Hoist by-divisor invariants and split mod-8 updates

.vscode/settings.json

@@ -9,7 +9,5 @@
 		"Mersenne",
 		"primality",
 		"suff"
-	],
-	"geminicodeassist.project": "evenperfectbitscanner",
-	"todo-tree.tree.showCountsInTree": true
+	]
 }

EvenPerfectBitScanner.Benchmarks/GpuModularArithmeticBenchmarks.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/GpuUInt128Montgomery64Benchmarks.cs

@@ -32,7 +32,7 @@ public class GpuUInt128Montgomery64Benchmarks
     [Benchmark(Baseline = true)]
     public ulong ExtensionMontgomeryMultiply()
     {
-        return Input.Left.MontgomeryMultiplyCpu(Input.Right, Input.Modulus, Input.NPrime);
+        return Input.Left.MontgomeryMultiply(Input.Right, Input.Modulus, Input.NPrime);
     }
 
     /// <summary>

EvenPerfectBitScanner.Benchmarks/MersenneDivisorCycleLengthGpuBenchmarks.cs

@@ -1,5 +1,6 @@
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
+using PerfectNumbers.Core;
 using BenchmarkDotNet.Jobs;
 
 namespace EvenPerfectBitScanner.Benchmarks;

EvenPerfectBitScanner.Benchmarks/Mod10Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod10_8_5_3Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using PerfectNumbers.Core;

EvenPerfectBitScanner.Benchmarks/Mod11Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod128Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod3Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod5Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod6Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod7Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/Mod8Benchmarks.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;

EvenPerfectBitScanner.Benchmarks/ModBenchmarkCase.cs

@@ -1,3 +1,5 @@
+using System;
+
 namespace EvenPerfectBitScanner.Benchmarks;
 
 public enum ModNumericType

EvenPerfectBitScanner.Benchmarks/MontgomeryMultiplyBenchmarks.cs

@@ -1,3 +1,4 @@
+using System;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 

EvenPerfectBitScanner.Benchmarks/MulMod64Benchmarks.Gpu.cs

@@ -1,8 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
 using System.Runtime.CompilerServices;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using ILGPU;
 using ILGPU.Runtime;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
 
 namespace EvenPerfectBitScanner.Benchmarks;

EvenPerfectBitScanner.Benchmarks/Pow2ModBenchmarks.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Buffers.Binary;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
@@ -100,7 +101,7 @@ public class Pow2ModBenchmarks
 
         for (int i = 0; i < SampleCount; i++)
         {
-            checksum ^= exponents[i].Pow2MontgomeryModWindowedConvertGpu(divisors[i]);
+            checksum ^= exponents[i].Pow2MontgomeryModWindowedGpu(divisors[i], keepMontgomery: false);
         }
 
         return checksum;
@@ -639,7 +640,7 @@ public class Pow2ModBenchmarks
         ulong nPrime = ComputeMontgomeryNPrime(modulus);
         ulong montgomeryOne = ComputeMontgomeryResidue(1UL, modulus);
         ulong montgomeryTwo = ComputeMontgomeryResidue(2UL, modulus);
-        ulong montgomeryTwoSquared = ULongExtensions.MontgomeryMultiplyCpu(montgomeryTwo, montgomeryTwo, modulus, nPrime);
+        ulong montgomeryTwoSquared = ULongExtensions.MontgomeryMultiply(montgomeryTwo, montgomeryTwo, modulus, nPrime);
 
         return new MontgomeryDivisorData(
             modulus,
@@ -735,22 +736,22 @@ public class Pow2ModBenchmarks
 
         if (exponent == 0UL)
         {
-            return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+            return result.MontgomeryMultiply(1UL, modulus, nPrime);
         }
 
         int msbIndex = 63 - BitOperations.LeadingZeroCount(exponent);
 
         for (int bitIndex = msbIndex; bitIndex >= 0; bitIndex--)
         {
-            result = result.MontgomeryMultiplyCpu(result, modulus, nPrime);
+            result = result.MontgomeryMultiply(result, modulus, nPrime);
 
             if (((exponent >> bitIndex) & 1UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(baseVal, modulus, nPrime);
+                result = result.MontgomeryMultiply(baseVal, modulus, nPrime);
             }
         }
 
-        return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+        return result.MontgomeryMultiply(1UL, modulus, nPrime);
     }
 
     private static ulong Pow2MontgomeryModBatched4(ulong exponent, in MontgomeryDivisorData divisor)
@@ -771,35 +772,35 @@ public class Pow2ModBenchmarks
             ulong nibble = remainingExponent & 0xFUL;
 
             ulong base0 = baseVal;
-            ulong base1 = base0.MontgomeryMultiplyCpu(base0, modulus, nPrime);
-            ulong base2 = base1.MontgomeryMultiplyCpu(base1, modulus, nPrime);
-            ulong base3 = base2.MontgomeryMultiplyCpu(base2, modulus, nPrime);
+            ulong base1 = base0.MontgomeryMultiply(base0, modulus, nPrime);
+            ulong base2 = base1.MontgomeryMultiply(base1, modulus, nPrime);
+            ulong base3 = base2.MontgomeryMultiply(base2, modulus, nPrime);
 
             if ((nibble & 1UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base0, modulus, nPrime);
+                result = result.MontgomeryMultiply(base0, modulus, nPrime);
             }
 
             if ((nibble & 2UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base1, modulus, nPrime);
+                result = result.MontgomeryMultiply(base1, modulus, nPrime);
             }
 
             if ((nibble & 4UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base2, modulus, nPrime);
+                result = result.MontgomeryMultiply(base2, modulus, nPrime);
             }
 
             if ((nibble & 8UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base3, modulus, nPrime);
+                result = result.MontgomeryMultiply(base3, modulus, nPrime);
             }
 
-            baseVal = base3.MontgomeryMultiplyCpu(base3, modulus, nPrime);
+            baseVal = base3.MontgomeryMultiply(base3, modulus, nPrime);
             remainingExponent >>= 4;
         }
 
-        return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+        return result.MontgomeryMultiply(1UL, modulus, nPrime);
     }
 
     private static ulong Pow2MontgomeryModSlidingWindow(ulong exponent, in MontgomeryDivisorData divisor)
@@ -816,16 +817,16 @@ public class Pow2ModBenchmarks
 
         if (exponent == 0UL)
         {
-            return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+            return result.MontgomeryMultiply(1UL, modulus, nPrime);
         }
 
         const int WindowSize = 5;
         Span<ulong> oddPowers = stackalloc ulong[1 << (WindowSize - 1)];
         oddPowers[0] = baseVal;
-        ulong baseSquared = baseVal.MontgomeryMultiplyCpu(baseVal, modulus, nPrime);
+        ulong baseSquared = baseVal.MontgomeryMultiply(baseVal, modulus, nPrime);
         for (int i = 1; i < oddPowers.Length; i++)
         {
-            oddPowers[i] = oddPowers[i - 1].MontgomeryMultiplyCpu(baseSquared, modulus, nPrime);
+            oddPowers[i] = oddPowers[i - 1].MontgomeryMultiply(baseSquared, modulus, nPrime);
         }
 
         int bitIndex = 63 - BitOperations.LeadingZeroCount(exponent);
@@ -834,7 +835,7 @@ public class Pow2ModBenchmarks
         {
             if (((exponent >> bitIndex) & 1UL) == 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(result, modulus, nPrime);
+                result = result.MontgomeryMultiply(result, modulus, nPrime);
                 bitIndex--;
                 continue;
             }
@@ -851,14 +852,14 @@ public class Pow2ModBenchmarks
             int squares = bitIndex - windowStart + 1;
             for (int i = 0; i < squares; i++)
             {
-                result = result.MontgomeryMultiplyCpu(result, modulus, nPrime);
+                result = result.MontgomeryMultiply(result, modulus, nPrime);
             }
 
-            result = result.MontgomeryMultiplyCpu(oddPowers[(int)(windowValue >> 1)], modulus, nPrime);
+            result = result.MontgomeryMultiply(oddPowers[(int)(windowValue >> 1)], modulus, nPrime);
             bitIndex = windowStart - 1;
         }
 
-        return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+        return result.MontgomeryMultiply(1UL, modulus, nPrime);
     }
 
     private static ulong Pow2ModBinary(ulong exponent, ulong modulus)

EvenPerfectBitScanner.Benchmarks/Pow2MontgomeryModBenchmarks.cs

@@ -77,7 +77,7 @@ public class Pow2MontgomeryModBenchmarks
 
         for (int i = 0; i < SampleCount; i++)
         {
-            checksum ^= exponents[i].Pow2MontgomeryModWindowedConvertGpu(divisors[i]);
+            checksum ^= exponents[i].Pow2MontgomeryModWindowedGpu(divisors[i], keepMontgomery: false);
         }
 
         return checksum;
@@ -262,7 +262,7 @@ public class Pow2MontgomeryModBenchmarks
         ulong nPrime = ComputeMontgomeryNPrime(modulus);
         ulong montgomeryOne = ComputeMontgomeryResidue(1UL, modulus);
         ulong montgomeryTwo = ComputeMontgomeryResidue(2UL, modulus);
-        ulong montgomeryTwoSquared = ULongExtensions.MontgomeryMultiplyCpu(montgomeryTwo, montgomeryTwo, modulus, nPrime);
+        ulong montgomeryTwoSquared = ULongExtensions.MontgomeryMultiply(montgomeryTwo, montgomeryTwo, modulus, nPrime);
 
         return new MontgomeryDivisorData(
             modulus,
@@ -300,22 +300,22 @@ public class Pow2MontgomeryModBenchmarks
 
         if (exponent == 0UL)
         {
-            return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+            return result.MontgomeryMultiply(1UL, modulus, nPrime);
         }
 
         int msbIndex = 63 - BitOperations.LeadingZeroCount(exponent);
 
         for (int bitIndex = msbIndex; bitIndex >= 0; bitIndex--)
         {
-            result = result.MontgomeryMultiplyCpu(result, modulus, nPrime);
+            result = result.MontgomeryMultiply(result, modulus, nPrime);
 
             if (((exponent >> bitIndex) & 1UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(baseVal, modulus, nPrime);
+                result = result.MontgomeryMultiply(baseVal, modulus, nPrime);
             }
         }
 
-        return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+        return result.MontgomeryMultiply(1UL, modulus, nPrime);
     }
 
     private static ulong Pow2MontgomeryModBatched4(ulong exponent, in MontgomeryDivisorData divisor)
@@ -336,35 +336,35 @@ public class Pow2MontgomeryModBenchmarks
             ulong nibble = remainingExponent & 0xFUL;
 
             ulong base0 = baseVal;
-            ulong base1 = base0.MontgomeryMultiplyCpu(base0, modulus, nPrime);
-            ulong base2 = base1.MontgomeryMultiplyCpu(base1, modulus, nPrime);
-            ulong base3 = base2.MontgomeryMultiplyCpu(base2, modulus, nPrime);
+            ulong base1 = base0.MontgomeryMultiply(base0, modulus, nPrime);
+            ulong base2 = base1.MontgomeryMultiply(base1, modulus, nPrime);
+            ulong base3 = base2.MontgomeryMultiply(base2, modulus, nPrime);
 
             if ((nibble & 1UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base0, modulus, nPrime);
+                result = result.MontgomeryMultiply(base0, modulus, nPrime);
             }
 
             if ((nibble & 2UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base1, modulus, nPrime);
+                result = result.MontgomeryMultiply(base1, modulus, nPrime);
             }
 
             if ((nibble & 4UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base2, modulus, nPrime);
+                result = result.MontgomeryMultiply(base2, modulus, nPrime);
             }
 
             if ((nibble & 8UL) != 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(base3, modulus, nPrime);
+                result = result.MontgomeryMultiply(base3, modulus, nPrime);
             }
 
-            baseVal = base3.MontgomeryMultiplyCpu(base3, modulus, nPrime);
+            baseVal = base3.MontgomeryMultiply(base3, modulus, nPrime);
             remainingExponent >>= 4;
         }
 
-        return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+        return result.MontgomeryMultiply(1UL, modulus, nPrime);
     }
 
 	// TODO: Update it with the latest implementations
@@ -382,16 +382,16 @@ public class Pow2MontgomeryModBenchmarks
 
         if (exponent == 0UL)
         {
-            return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+            return result.MontgomeryMultiply(1UL, modulus, nPrime);
         }
 
         const int WindowSize = 5;
         Span<ulong> oddPowers = stackalloc ulong[1 << (WindowSize - 1)];
         oddPowers[0] = baseVal;
-        ulong baseSquared = baseVal.MontgomeryMultiplyCpu(baseVal, modulus, nPrime);
+        ulong baseSquared = baseVal.MontgomeryMultiply(baseVal, modulus, nPrime);
         for (int i = 1; i < oddPowers.Length; i++)
         {
-            oddPowers[i] = oddPowers[i - 1].MontgomeryMultiplyCpu(baseSquared, modulus, nPrime);
+            oddPowers[i] = oddPowers[i - 1].MontgomeryMultiply(baseSquared, modulus, nPrime);
         }
 
         int bitIndex = 63 - BitOperations.LeadingZeroCount(exponent);
@@ -400,7 +400,7 @@ public class Pow2MontgomeryModBenchmarks
         {
             if (((exponent >> bitIndex) & 1UL) == 0UL)
             {
-                result = result.MontgomeryMultiplyCpu(result, modulus, nPrime);
+                result = result.MontgomeryMultiply(result, modulus, nPrime);
                 bitIndex--;
                 continue;
             }
@@ -417,14 +417,14 @@ public class Pow2MontgomeryModBenchmarks
             int squares = bitIndex - windowStart + 1;
             for (int i = 0; i < squares; i++)
             {
-                result = result.MontgomeryMultiplyCpu(result, modulus, nPrime);
+                result = result.MontgomeryMultiply(result, modulus, nPrime);
             }
 
-            result = result.MontgomeryMultiplyCpu(oddPowers[(int)(windowValue >> 1)], modulus, nPrime);
+            result = result.MontgomeryMultiply(oddPowers[(int)(windowValue >> 1)], modulus, nPrime);
             bitIndex = windowStart - 1;
         }
 
-        return result.MontgomeryMultiplyCpu(1UL, modulus, nPrime);
+        return result.MontgomeryMultiply(1UL, modulus, nPrime);
     }
 
 	// TODO: Update it with the latest implementations, if it exists in production code. Otherwise just remove TODO

EvenPerfectBitScanner.Benchmarks/Pow2MontgomeryModWindowedBenchmarkData.cs

@@ -1,3 +1,4 @@
+using System;
 using PerfectNumbers.Core;
 
 namespace EvenPerfectBitScanner.Benchmarks;

EvenPerfectBitScanner.Benchmarks/Pow2MontgomeryModWindowedKeepMontgomeryGpuBenchmarks.cs

@@ -1,3 +1,4 @@
+using System;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using PerfectNumbers.Core;
@@ -33,7 +34,7 @@ public class Pow2MontgomeryModWindowedKeepMontgomeryGpuBenchmarks
         for (int i = 0; i < cases.Length; i++)
         {
             ref readonly Pow2MontgomeryModWindowedBenchmarkCase current = ref cases[i];
-            checksum ^= current.Exponent.Pow2MontgomeryModWindowedConvertGpu(current.Divisor);
+            checksum ^= current.Exponent.Pow2MontgomeryModWindowedGpu(current.Divisor, keepMontgomery: false);
         }
 
         return checksum;
@@ -51,7 +52,7 @@ public class Pow2MontgomeryModWindowedKeepMontgomeryGpuBenchmarks
         for (int i = 0; i < cases.Length; i++)
         {
             ref readonly Pow2MontgomeryModWindowedBenchmarkCase current = ref cases[i];
-            checksum ^= current.Exponent.Pow2MontgomeryModWindowedKeepGpu(current.Divisor);
+            checksum ^= current.Exponent.Pow2MontgomeryModWindowedGpu(current.Divisor, keepMontgomery: true);
         }
 
         return checksum;

EvenPerfectBitScanner.Benchmarks/PrimeTesterBenchmarks.cs

@@ -1,8 +1,10 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using Open.Numeric.Primes;
 using PerfectNumbers.Core;
-using PerfectNumbers.Core.Gpu.Accelerators;
 
 namespace EvenPerfectBitScanner.Benchmarks;
 
@@ -10,7 +12,8 @@ namespace EvenPerfectBitScanner.Benchmarks;
 [MemoryDiagnoser]
 public class PrimeTesterBenchmarks
 {
-    private static readonly HeuristicPrimeTester _heuristicTester = new();
+    private HeuristicPrimeTester _cpuTester = null!;
+    private HeuristicPrimeTester _gpuTester = null!;
     private ulong[] _candidates = [];
 
     [ParamsSource(nameof(GetBenchmarkCases))]
@@ -19,6 +22,8 @@ public class PrimeTesterBenchmarks
     [GlobalSetup]
     public void GlobalSetup()
     {
+        _cpuTester = new HeuristicPrimeTester();
+        _gpuTester = new HeuristicPrimeTester();
         _candidates = BenchmarkCase.Candidates;
 
         if (_candidates.Length == 0)
@@ -26,23 +31,23 @@ public class PrimeTesterBenchmarks
             return;
         }
 
-		PrimeOrderCalculatorAccelerator.WarmUp();
-		// HeuristicGroupABPrimeTesterAccelerator.WarmUp();
-        _ = HeuristicPrimeTester.IsPrimeCpu(_candidates[0]);
-        _ = HeuristicPrimeTester.IsPrimeGpu(_candidates[0]);
+        CancellationToken cancellationToken = CancellationToken.None;
+        _cpuTester.IsPrimeCpu(_candidates[0], cancellationToken);
+        _gpuTester.IsPrimeGpu(_candidates[0]);
         _ = Prime.Numbers.IsPrime(_candidates[0]);
     }
 
-    // [Benchmark]
+    [Benchmark(Baseline = true)]
     public int HeuristicCpu()
     {
-        HeuristicPrimeTester tester = _heuristicTester;
+        HeuristicPrimeTester tester = _cpuTester;
         ulong[] values = _candidates;
+        CancellationToken cancellationToken = CancellationToken.None;
         int primeCount = 0;
 
         for (int i = 0; i < values.Length; i++)
         {
-            if (HeuristicPrimeTester.IsPrimeCpu(values[i]))
+            if (tester.IsPrimeCpu(values[i], cancellationToken))
             {
                 primeCount++;
             }
@@ -54,13 +59,14 @@ public class PrimeTesterBenchmarks
     [Benchmark]
     public int HeuristicGpu()
     {
-        HeuristicPrimeTester tester = _heuristicTester;
+        HeuristicPrimeTester tester = _gpuTester;
         ulong[] values = _candidates;
+        CancellationToken cancellationToken = CancellationToken.None;
         int primeCount = 0;
 
         for (int i = 0; i < values.Length; i++)
         {
-            if (HeuristicPrimeTester.IsPrimeGpu(values[i]))
+            if (tester.IsPrimeGpu(values[i]))
             {
                 primeCount++;
             }
@@ -69,49 +75,18 @@ public class PrimeTesterBenchmarks
         return primeCount;
     }
 
-    [Benchmark]
-    public int HeuristicCombinedGpu()
-    {
-        ulong[] values = _candidates;
-        int primeCount = 0;
-
-        for (int i = 0; i < values.Length; i++)
-        {
-            if (HeuristicCombinedPrimeTester.IsPrimeGpu(values[i]))
-            {
-                primeCount++;
-            }
-        }
-
-        return primeCount;
-    }
-
-    [Benchmark]
-    public int HeuristicCombinedCpu()
-    {
-        ulong[] values = _candidates;
-        int primeCount = 0;
-
-        for (int i = 0; i < values.Length; i++)
-        {
-            if (HeuristicCombinedPrimeTester.IsPrimeCpu(values[i]))
-            {
-                primeCount++;
-            }
-        }
-
-        return primeCount;
-    }
-
-    [Benchmark]
+    // This benchmark is very slow. No point in comparing it.
+    // [Benchmark]
     public int NonHeuristicGpu()
-	{
+    {
+        // PrimeTester tester = _gpuTester;
         ulong[] values = _candidates;
+        CancellationToken cancellationToken = CancellationToken.None;
         int primeCount = 0;
 
         for (int i = 0; i < values.Length; i++)
         {
-            if (PrimeTester.IsPrimeGpu(values[i]))
+            if (PrimeTester.Exclusive.IsPrimeGpu(values[i], cancellationToken))
             {
                 primeCount++;
             }
@@ -120,15 +95,17 @@ public class PrimeTesterBenchmarks
         return primeCount;
     }
 
-    [Benchmark(Baseline = true)]
+    [Benchmark]
     public int NonHeuristicCpu()
     {
+        // PrimeTester tester = _gpuTester;
         ulong[] values = _candidates;
+        CancellationToken cancellationToken = CancellationToken.None;
         int primeCount = 0;
 
         for (int i = 0; i < values.Length; i++)
         {
-            if (PrimeTester.IsPrime(values[i]))
+            if (PrimeTester.IsPrimeCpu(values[i], cancellationToken))
             {
                 primeCount++;
             }
@@ -137,7 +114,7 @@ public class PrimeTesterBenchmarks
         return primeCount;
     }
 
-    // [Benchmark]
+    [Benchmark]
     public int OpenNumericPrimes()
     {
         ulong[] values = _candidates;

EvenPerfectBitScanner.ResultsParser/Program.cs

@@ -19,7 +19,7 @@ internal static class Program
 				"/help"
 		};
 
-private const string DefaultHeader = "p,divisor,searchedMersenne,detailedCheck,passedAllTests";
+	private const string DefaultHeader = "p,searchedMersenne,detailedCheck,passedAllTests";
 
 	private static int Main(string[] args)
 	{

EvenPerfectBitScanner.Tests/ProgramTests.cs

@@ -3,9 +3,13 @@ using Xunit;
 using System.Reflection;
 using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
+
+using EvenPerfectBitScanner;
 using EvenPerfectBitScanner.Candidates;
 using EvenPerfectBitScanner.Candidates.Transforms;
 using System.Numerics;
+using System.Threading;
+using System.Threading.Tasks;
 
 namespace EvenPerfectBitScanner.Tests;
 
@@ -51,7 +55,7 @@ public class ProgramTests
     [InlineData(81UL, false)]
     public void IsPrime_identifies_primes_correctly(ulong n, bool expected)
     {
-        PrimeTester.IsPrime(n).Should().Be(expected);
+        new PrimeTester().IsPrime(n, CancellationToken.None).Should().Be(expected);
     }
 
     [Fact]
@@ -98,11 +102,13 @@ public class ProgramTests
         var testerField = typeof(Program).GetField("_divisorTester", BindingFlags.NonPublic | BindingFlags.Static)!;
         var candidatesField = typeof(MersenneNumberDivisorGpuTester).GetField("_divisorCandidates", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         testerField.SetValue(null, new MersenneNumberDivisorGpuTester());
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
         candidatesField.SetValue(null, new (ulong, uint)[] { (7UL, 3U), (23UL, 11U) });
+        forceCpuProp!.SetValue(null, true);
 
         try
         {
@@ -116,6 +122,7 @@ public class ProgramTests
             candidatesField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -128,11 +135,13 @@ public class ProgramTests
         var testerField = typeof(Program).GetField("_divisorTester", BindingFlags.NonPublic | BindingFlags.Static)!;
         var candidatesField = typeof(MersenneNumberDivisorGpuTester).GetField("_divisorCandidates", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         testerField.SetValue(null, new MersenneNumberDivisorGpuTester());
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
         candidatesField.SetValue(null, Array.Empty<(ulong, uint)>());
+        forceCpuProp!.SetValue(null, true);
 
         try
         {
@@ -146,6 +155,7 @@ public class ProgramTests
             candidatesField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -158,10 +168,12 @@ public class ProgramTests
 
         var testerField = typeof(Program).GetField("_divisorTester", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         testerField.SetValue(null, new MersenneNumberDivisorGpuTester());
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, true);
 
         try
         {
@@ -174,6 +186,7 @@ public class ProgramTests
             testerField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -186,10 +199,12 @@ public class ProgramTests
 
         var testerField = typeof(Program).GetField("_divisorTester", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         testerField.SetValue(null, new MersenneNumberDivisorGpuTester());
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, false);
 
         try
         {
@@ -206,6 +221,7 @@ public class ProgramTests
             testerField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -217,10 +233,12 @@ public class ProgramTests
 
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(useIncremental: true, useResidue: true, maxK: 1_000UL), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, false);
 
         try
         {
@@ -237,6 +255,7 @@ public class ProgramTests
             mersenneField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -248,6 +267,7 @@ public class ProgramTests
 
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(
             useIncremental: true,
@@ -255,6 +275,7 @@ public class ProgramTests
             maxK: 1_024UL), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, false);
 
         try
         {
@@ -271,6 +292,7 @@ public class ProgramTests
             mersenneField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -283,6 +305,7 @@ public class ProgramTests
 
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(
             useIncremental: true,
@@ -290,6 +313,7 @@ public class ProgramTests
             maxK: 5_000_000UL), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, false);
 
         try
         {
@@ -306,6 +330,7 @@ public class ProgramTests
             mersenneField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -317,6 +342,7 @@ public class ProgramTests
 
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(
             useIncremental: true,
@@ -324,6 +350,7 @@ public class ProgramTests
             maxK: 5_000_000UL), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, false);
 
         try
         {
@@ -340,6 +367,7 @@ public class ProgramTests
             mersenneField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -352,6 +380,7 @@ public class ProgramTests
 
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(
             useIncremental: true,
@@ -361,6 +390,7 @@ public class ProgramTests
             maxK: 1_024UL), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, exponent, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, true);
 
         try
         {
@@ -372,6 +402,7 @@ public class ProgramTests
             mersenneField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }
@@ -386,6 +417,7 @@ public class ProgramTests
 
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(
             useIncremental: false,
@@ -396,6 +428,7 @@ public class ProgramTests
             maxK: configuration.ResidueMaxK), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, exponent, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, false);
 
         try
         {
@@ -407,7 +440,9 @@ public class ProgramTests
             mersenneField.SetValue(null, null);
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
+            GpuContextPool.DisposeAll();
         }
     }
 
@@ -471,10 +506,12 @@ public class ProgramTests
         var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
         var compositeField = typeof(Program).GetField("_lastCompositeP", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
 
         mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(useIncremental: true, useResidue: false, maxK: 1_000UL), trackAllValues: true));
         primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
         CandidatesCalculator.OverrideResidueTrackers(new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
+        forceCpuProp!.SetValue(null, true);
 
         try
         {
@@ -495,6 +532,7 @@ public class ProgramTests
             primeField.SetValue(null, null);
             CandidatesCalculator.ResetResidueTrackers();
             compositeField.SetValue(null, false);
+            forceCpuProp!.SetValue(null, false);
             ResetCliArguments();
         }
     }

EvenPerfectBitScanner.Tests/ResultsFileNameTests.cs

@@ -1,3 +1,6 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Numerics;
 using FluentAssertions;
 using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;

EvenPerfectBitScanner/CalculationResultHandler.cs

@@ -1,13 +1,15 @@
 using System.Buffers.Text;
+using System.IO;
 using System.Runtime.CompilerServices;
 using System.Text;
+using System.Threading;
 using PerfectNumbers.Core;
 
 namespace EvenPerfectBitScanner;
 
 internal static class CalculationResultHandler
 {
-        private const string ResultsHeader = "p,divisor,searchedMersenne,detailedCheck,passedAllTests";
+        private const string ResultsHeader = "p,searchedMersenne,detailedCheck,passedAllTests";
         private const string PrimeFoundSuffix = " (FOUND VALID CANDIDATES)";
         internal const int DefaultWriteBatchSize = 100;
 
@@ -93,19 +95,19 @@ internal static class CalculationResultHandler
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal static void HandleResult(ulong currentP, ulong divisor, bool searchedMersenne, bool detailedCheck, bool passedAllTests, bool lastWasComposite)
+        internal static void HandleResult(ulong currentP, bool searchedMersenne, bool detailedCheck, bool passedAllTests, bool lastWasComposite)
         {
                 // Program flow ensures Initialize(...) and InitializeOutputBuffer() ran before this call. Do not add initialization guards here.
 
                 Span<byte> stackBuffer = stackalloc byte[128];
                 byte[]? rentedBuffer = null;
                 Span<byte> utf8Span = stackBuffer;
-                int byteCount = TryFormatResultLine(utf8Span, currentP, divisor, searchedMersenne, detailedCheck, passedAllTests);
+                int byteCount = TryFormatResultLine(utf8Span, currentP, searchedMersenne, detailedCheck, passedAllTests);
                 if (byteCount < 0)
                 {
                         rentedBuffer = ThreadStaticPools.BytePool.Rent(256);
                         utf8Span = rentedBuffer;
-                        byteCount = TryFormatResultLine(utf8Span, currentP, divisor, searchedMersenne, detailedCheck, passedAllTests);
+                        byteCount = TryFormatResultLine(utf8Span, currentP, searchedMersenne, detailedCheck, passedAllTests);
                         if (byteCount < 0)
                         {
                                 ThreadStaticPools.BytePool.Return(rentedBuffer);
@@ -229,7 +231,7 @@ internal static class CalculationResultHandler
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static int TryFormatResultLine(Span<byte> destination, ulong currentP, ulong divisor, bool searchedMersenne, bool detailedCheck, bool passedAllTests)
+        private static int TryFormatResultLine(Span<byte> destination, ulong currentP, bool searchedMersenne, bool detailedCheck, bool passedAllTests)
         {
                 int offset = 0;
 
@@ -246,19 +248,6 @@ internal static class CalculationResultHandler
 
                 destination[offset++] = (byte)',';
 
-                if (!Utf8Formatter.TryFormat(divisor, destination[offset..], out written))
-                {
-                        return -1;
-                }
-
-                offset += written;
-                if (offset >= destination.Length)
-                {
-                        return -1;
-                }
-
-                destination[offset++] = (byte)',';
-
                 if (!Utf8Formatter.TryFormat(searchedMersenne, destination[offset..], out written))
                 {
                         return -1;

EvenPerfectBitScanner/Candidates/CalculationTestTime.cs

@@ -1,4 +1,5 @@
 using System.Globalization;
+using System.IO;
 
 namespace EvenPerfectBitScanner.Candidates;
 

EvenPerfectBitScanner/Candidates/CandidatesCalculator.cs

@@ -1,4 +1,5 @@
 using System.Runtime.CompilerServices;
+using System.Threading;
 using Open.Numeric.Primes;
 using PerfectNumbers.Core;
 using EvenPerfectBitScanner.Candidates.Transforms;

EvenPerfectBitScanner/Candidates/Transforms/CandidateAddPrimesTransform.cs

@@ -1,4 +1,6 @@
 using System.Runtime.CompilerServices;
+using System.Threading;
+using EvenPerfectBitScanner.Candidates;
 using Open.Numeric.Primes;
 
 namespace EvenPerfectBitScanner.Candidates.Transforms;

EvenPerfectBitScanner/Candidates/Transforms/CandidateAddTransform.cs

@@ -1,4 +1,6 @@
 using System.Runtime.CompilerServices;
+using System.Threading;
+using EvenPerfectBitScanner.Candidates;
 
 namespace EvenPerfectBitScanner.Candidates.Transforms;
 

EvenPerfectBitScanner/Candidates/Transforms/CandidateBitTransform.cs

@@ -1,4 +1,5 @@
 using System.Runtime.CompilerServices;
+using System.Threading;
 
 namespace EvenPerfectBitScanner.Candidates.Transforms;
 

EvenPerfectBitScanner/CliArguments.cs

@@ -1,4 +1,6 @@
+using System;
 using System.Globalization;
+using System.Numerics;
 using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
 
@@ -200,15 +202,14 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--prime=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> primeValue = argument.AsSpan("--prime=".Length);
-                startPrime = Utf8CliParser.ParseUInt64(primeValue);
+                startPrime = Utf8CliParser.ParseUInt64(argument.AsSpan(argument.IndexOf('=') + 1));
                 startPrimeProvided = true;
                 continue;
             }
 
             if (argument.StartsWith("--max-prime=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> value = argument.AsSpan("--max-prime=".Length);
+                ReadOnlySpan<char> value = argument.AsSpan(argument.IndexOf('=') + 1);
                 if (UInt128.TryParse(value, NumberStyles.None, CultureInfo.InvariantCulture, out UInt128 parsedMaxPrime))
                 {
                     maxPrimeLimit = parsedMaxPrime;
@@ -237,13 +238,13 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--threads=", StringComparison.OrdinalIgnoreCase))
             {
-                threadCount = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--threads=".Length)));
+                threadCount = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--mersenne=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> value = argument.AsSpan("--mersenne=".Length);
+                ReadOnlySpan<char> value = argument.AsSpan(argument.IndexOf('=') + 1);
                 if (value.Equals("pow2mod", StringComparison.OrdinalIgnoreCase))
                 {
                     kernelType = GpuKernelType.Pow2Mod;
@@ -280,7 +281,7 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--divisor-cycles-limit=", StringComparison.OrdinalIgnoreCase))
             {
-                if (Utf8CliParser.TryParseUInt64(argument.AsSpan("--divisor-cycles-limit=".Length), out ulong parsedLimit))
+                if (Utf8CliParser.TryParseUInt64(argument.AsSpan(argument.IndexOf('=') + 1), out ulong parsedLimit))
                 {
                     divisorCyclesSearchLimit = parsedLimit;
                 }
@@ -290,7 +291,7 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--residue-max-k=", StringComparison.OrdinalIgnoreCase))
             {
-                if (Utf8CliParser.TryParseUInt64(argument.AsSpan("--residue-max-k=".Length), out ulong parsedResidueMax))
+                if (Utf8CliParser.TryParseUInt64(argument.AsSpan(argument.IndexOf('=') + 1), out ulong parsedResidueMax))
                 {
                     residueKMax = parsedResidueMax;
                 }
@@ -300,7 +301,7 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--mersenne-device=", StringComparison.OrdinalIgnoreCase))
             {
-                useMersenneOnGpu = !argument.AsSpan("--mersenne-device=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
+                useMersenneOnGpu = !argument.AsSpan(argument.IndexOf('=') + 1).Equals("cpu", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
@@ -318,7 +319,7 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--order-warmup-limit=", StringComparison.OrdinalIgnoreCase))
             {
-                if (Utf8CliParser.TryParseUInt64(argument.AsSpan("--order-warmup-limit=".Length), out ulong parsedLimit))
+                if (Utf8CliParser.TryParseUInt64(argument.AsSpan(argument.IndexOf('=') + 1), out ulong parsedLimit))
                 {
                     orderWarmupLimitOverride = parsedLimit;
                 }
@@ -334,14 +335,14 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--ntt=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> value = argument.AsSpan("--ntt=".Length);
+                ReadOnlySpan<char> value = argument.AsSpan(argument.IndexOf('=') + 1);
                 nttBackend = value.Equals("staged", StringComparison.OrdinalIgnoreCase) ? NttBackend.Staged : NttBackend.Reference;
                 continue;
             }
 
             if (argument.StartsWith("--mod-reduction=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> value = argument.AsSpan("--mod-reduction=".Length);
+                ReadOnlySpan<char> value = argument.AsSpan(argument.IndexOf('=') + 1);
                 if (value.Equals("mont64", StringComparison.OrdinalIgnoreCase))
                 {
                     modReductionMode = ModReductionMode.Mont64;
@@ -364,25 +365,25 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--primes-device=", StringComparison.OrdinalIgnoreCase))
             {
-                forcePrimeKernelsOnCpu = argument.AsSpan("--primes-device=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
+                forcePrimeKernelsOnCpu = argument.AsSpan(argument.IndexOf('=') + 1).Equals("cpu", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
             if (argument.StartsWith("--order-device=", StringComparison.OrdinalIgnoreCase))
             {
-                useOrderOnGpu = !argument.AsSpan("--order-device=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
+                useOrderOnGpu = !argument.AsSpan(argument.IndexOf('=') + 1).Equals("cpu", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
             if (argument.StartsWith("--rle-blacklist=", StringComparison.OrdinalIgnoreCase))
             {
-                rleBlacklistPath = argument["--rle-blacklist=".Length..];
+                rleBlacklistPath = argument[(argument.IndexOf('=') + 1)..];
                 continue;
             }
 
             if (argument.StartsWith("--rle-hard-max=", StringComparison.OrdinalIgnoreCase))
             {
-                if (Utf8CliParser.TryParseUInt64(argument.AsSpan("--rle-hard-max=".Length), out ulong parsedMax))
+                if (Utf8CliParser.TryParseUInt64(argument.AsSpan(argument.IndexOf('=') + 1), out ulong parsedMax))
                 {
                     rleHardMaxP = parsedMax;
                 }
@@ -392,14 +393,14 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--rle-only-last7=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> value = argument.AsSpan("--rle-only-last7=".Length);
+                ReadOnlySpan<char> value = argument.AsSpan(argument.IndexOf('=') + 1);
                 rleOnlyLast7 = !value.Equals("false", StringComparison.OrdinalIgnoreCase) && !value.Equals("0", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
             if (argument.StartsWith("--zero-hard=", StringComparison.OrdinalIgnoreCase))
             {
-                if (Utf8CliParser.TryParseDouble(argument.AsSpan("--zero-hard=".Length), out double zeroFraction))
+                if (Utf8CliParser.TryParseDouble(argument.AsSpan(argument.IndexOf('=') + 1), out double zeroFraction))
                 {
                     zeroFractionHard = zeroFraction;
                 }
@@ -409,7 +410,7 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--zero-conj=", StringComparison.OrdinalIgnoreCase))
             {
-                ReadOnlySpan<char> value = argument.AsSpan("--zero-conj=".Length);
+                ReadOnlySpan<char> value = argument.AsSpan(argument.IndexOf('=') + 1);
                 int colon = value.IndexOf(':');
                 if (colon > 0)
                 {
@@ -426,97 +427,87 @@ internal readonly struct CliArguments
 
             if (argument.StartsWith("--lucas=", StringComparison.OrdinalIgnoreCase))
             {
-                useMersenneOnGpu = !argument.AsSpan("--lucas=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
+                useMersenneOnGpu = !argument.AsSpan(argument.IndexOf('=') + 1).Equals("cpu", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
-            if (argument.StartsWith("--primes=", StringComparison.OrdinalIgnoreCase))
+            if (argument.StartsWith("--primes=", StringComparison.OrdinalIgnoreCase) ||
+                argument.StartsWith("--gpu-kernels=", StringComparison.OrdinalIgnoreCase) ||
+                argument.StartsWith("--accelerator=", StringComparison.OrdinalIgnoreCase))
             {
-                forcePrimeKernelsOnCpu = argument.AsSpan("--primes=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
-                continue;
-            }
-
-            if (argument.StartsWith("--gpu-kernels=", StringComparison.OrdinalIgnoreCase))
-            {
-                forcePrimeKernelsOnCpu = argument.AsSpan("--gpu-kernels=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
-                continue;
-            }
-
-            if (argument.StartsWith("--accelerator=", StringComparison.OrdinalIgnoreCase))
-            {
-                forcePrimeKernelsOnCpu = argument.AsSpan("--accelerator=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
+                forcePrimeKernelsOnCpu = argument.AsSpan(argument.IndexOf('=') + 1).Equals("cpu", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
             if (argument.StartsWith("--results-dir=", StringComparison.OrdinalIgnoreCase))
             {
-                resultsDirectory = argument["--results-dir=".Length..];
+                resultsDirectory = argument[(argument.IndexOf('=') + 1)..];
                 continue;
             }
 
             if (argument.StartsWith("--results-prefix=", StringComparison.OrdinalIgnoreCase))
             {
-                resultsPrefix = argument["--results-prefix=".Length..];
+                resultsPrefix = argument[(argument.IndexOf('=') + 1)..];
                 continue;
             }
 
             if (argument.StartsWith("--gpu-prime-threads=", StringComparison.OrdinalIgnoreCase))
             {
-                gpuPrimeThreads = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--gpu-prime-threads=".Length)));
+                gpuPrimeThreads = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--gpu-prime-batch=", StringComparison.OrdinalIgnoreCase))
             {
-                gpuPrimeBatch = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--gpu-prime-batch=".Length)));
+                gpuPrimeBatch = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--ll-slice=", StringComparison.OrdinalIgnoreCase))
             {
-                sliceSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--ll-slice=".Length)));
+                sliceSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--gpu-scan-batch=", StringComparison.OrdinalIgnoreCase))
             {
-                scanBatchSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--gpu-scan-batch=".Length)));
+                scanBatchSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--block-size=", StringComparison.OrdinalIgnoreCase))
             {
-                blockSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--block-size=".Length)));
+                blockSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--filter-p=", StringComparison.OrdinalIgnoreCase))
             {
-                filterFile = argument["--filter-p=".Length..];
+                filterFile = argument[(argument.IndexOf('=') + 1)..];
                 continue;
             }
 
             if (argument.StartsWith("--write-batch-size=", StringComparison.OrdinalIgnoreCase))
             {
-                writeBatchSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--write-batch-size=".Length)));
+                writeBatchSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 
             if (argument.StartsWith("--divisor-cycles=", StringComparison.OrdinalIgnoreCase))
             {
-                cyclesPath = argument["--divisor-cycles=".Length..];
+                cyclesPath = argument[(argument.IndexOf('=') + 1)..];
                 continue;
             }
 
             if (argument.StartsWith("--divisor-cycles-device=", StringComparison.OrdinalIgnoreCase))
             {
-                useGpuCycles = !argument.AsSpan("--divisor-cycles-device=".Length).Equals("cpu", StringComparison.OrdinalIgnoreCase);
+                useGpuCycles = !argument.AsSpan(argument.IndexOf('=') + 1).Equals("cpu", StringComparison.OrdinalIgnoreCase);
                 continue;
             }
 
             if (argument.StartsWith("--divisor-cycles-batch=", StringComparison.OrdinalIgnoreCase))
             {
-                cyclesBatchSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan("--divisor-cycles-batch=".Length)));
+                cyclesBatchSize = Math.Max(1, Utf8CliParser.ParseInt32(argument.AsSpan(argument.IndexOf('=') + 1)));
                 continue;
             }
 

EvenPerfectBitScanner/IO/CalculationResultsFile.cs

@@ -1,6 +1,7 @@
 using Open.Collections;
 using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
+using EvenPerfectBitScanner;
 
 namespace EvenPerfectBitScanner.IO;
 
@@ -13,7 +14,7 @@ internal static class CalculationResultsFile
                 using FileStream readStream = new(candidateFile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
                 using StreamReader reader = new(readStream);
                 string? line;
-                ReadOnlySpan<char> trimmed;
+                ReadOnlySpan<char> span;
                 while ((line = reader.ReadLine()) is not null)
                 {
                         if (string.IsNullOrWhiteSpace(line))
@@ -21,67 +22,36 @@ internal static class CalculationResultsFile
                                 continue;
                         }
 
-                        trimmed = line.AsSpan().Trim();
-                        if (trimmed.IsEmpty || trimmed[0] == '#')
+                        span = line.AsSpan().Trim();
+                        if (span.IsEmpty || span[0] == '#')
                         {
                                 continue;
                         }
-
-                        int length = trimmed.Length;
                         int index = 0;
-                        if (!maxPrimeConfigured)
+                        while (index < span.Length)
                         {
-                                while (index < length)
+                                if (!char.IsDigit(span[index]))
                                 {
-                                        char current = trimmed[index];
-                                        uint digit = (uint)(current - '0');
-                                        if (digit > 9U)
-                                        {
-                                                index++;
-                                                continue;
-                                        }
+                                        index++;
+                                        continue;
+                                }
 
-                                        int start = index++;
-                                        while (index < length && (uint)(trimmed[index] - '0') <= 9U)
-                                        {
-                                                index++;
-                                        }
+                                int start = index;
+                                index++;
+                                while (index < span.Length && char.IsDigit(span[index]))
+                                {
+                                        index++;
+                                }
 
-                                        if (Utf8CliParser.TryParseUInt64(trimmed[start..index], out ulong parsed))
+                                if (Utf8CliParser.TryParseUInt64(span[start..index], out ulong parsed))
+                                {
+                                        if (!maxPrimeConfigured || (UInt128)parsed <= maxPrimeLimit)
                                         {
                                                 candidates.Add(parsed);
                                         }
-                                }
-                        }
-                        else
-                        {
-                                UInt128 limit = maxPrimeLimit;
-                                while (index < length)
-                                {
-                                        char current = trimmed[index];
-                                        uint digit = (uint)(current - '0');
-                                        if (digit > 9U)
+                                        else
                                         {
-                                                index++;
-                                                continue;
-                                        }
-
-                                        int start = index++;
-                                        while (index < length && (uint)(trimmed[index] - '0') <= 9U)
-                                        {
-                                                index++;
-                                        }
-
-                                        if (Utf8CliParser.TryParseUInt64(trimmed[start..index], out ulong parsed))
-                                        {
-                                                if ((UInt128)parsed <= limit)
-                                                {
-                                                        candidates.Add(parsed);
-                                                }
-                                                else
-                                                {
-                                                        skippedByLimit++;
-                                                }
+                                                skippedByLimit++;
                                         }
                                 }
                         }
@@ -100,7 +70,6 @@ internal static class CalculationResultsFile
                 int first = 0;
                 int second = 0;
                 int third = 0;
-                int fourth = 0;
                 ulong parsedP = 0UL;
                 ReadOnlySpan<char> detailedSpan = default;
                 ReadOnlySpan<char> passedAllTestsSpan = default;
@@ -140,15 +109,8 @@ internal static class CalculationResultsFile
                                 continue;
                         }
 
-                        span = span[(third + 1)..];
-                        fourth = span.IndexOf(',');
-                        if (fourth < 0)
-                        {
-                                continue;
-                        }
-
-                        detailedSpan = span[..fourth];
-                        passedAllTestsSpan = span[(fourth + 1)..];
+                        detailedSpan = span[..third];
+                        passedAllTestsSpan = span[(third + 1)..];
 
                         if (Utf8CliParser.TryParseBoolean(detailedSpan, out detailed) && Utf8CliParser.TryParseBoolean(passedAllTestsSpan, out passedAllTests))
                         {

EvenPerfectBitScanner/Program.cs

@@ -12,7 +12,7 @@ namespace EvenPerfectBitScanner;
 
 internal static class Program
 {
-	// private static ThreadLocal<PrimeTester> PrimeTesters = null!;
+	private static ThreadLocal<PrimeTester> PrimeTesters = null!;
 	private static ThreadLocal<MersenneNumberTester> MersenneTesters = null!;
 	private const ulong InitialP = PerfectNumberConstants.BiggestKnownEvenPerfectP;
 	private static MersenneNumberDivisorGpuTester? _divisorTester;
@@ -28,8 +28,6 @@ internal static class Program
 	[ThreadStatic]
 	private static bool _lastCompositeP;
 
-	private static bool _runPrimesOnCpu;
-
 	private static void Main(string[] args)
 	{
 		try
@@ -51,24 +49,18 @@ internal static class Program
 
 			NttGpuMath.GpuTransformBackend = _cliArguments.NttBackend;
 			NttGpuMath.ReductionMode = _cliArguments.ModReductionMode;
-			_runPrimesOnCpu = _cliArguments.ForcePrimeKernelsOnCpu;
+			GpuContextPool.ForceCpu = _cliArguments.ForcePrimeKernelsOnCpu;
 
 			ulong currentP = _cliArguments.StartPrime;
 			ulong remainder = currentP % 6UL;
 			bool startPrimeProvided = _cliArguments.StartPrimeProvided;
 			int threadCount = Math.Max(1, _cliArguments.ThreadCount);
-			int gpuPrimeBatch = Math.Max(1, _cliArguments.GpuPrimeBatch);
-			// int gpuPrimeThreads = SharedGpuContext.Device.MaxNumThreads;
-			int gpuPrimeThreads = Math.Max(1, _cliArguments.GpuPrimeThreads);
 			UnboundedTaskScheduler.ConfigureThreadCount(threadCount);
-			PrimeTester.GpuBatchSize = gpuPrimeBatch;
-			GpuPrimeWorkLimiter.SetLimit(gpuPrimeThreads);
-			Console.WriteLine("Warming up GPU kernels");
-			PrimeTester.WarmUpGpuKernels(1024);			
-			// PrimeTester.WarmUpGpuKernels(gpuPrimeThreads >> 4);
 			Console.WriteLine("Starting up threads...");
 			_ = UnboundedTaskScheduler.Instance;
 			int blockSize = Math.Max(1, _cliArguments.BlockSize);
+			int gpuPrimeThreads = Math.Max(1, _cliArguments.GpuPrimeThreads);
+			int gpuPrimeBatch = Math.Max(1, _cliArguments.GpuPrimeBatch);
 			GpuKernelType kernelType = _cliArguments.KernelType;
 			bool useBitTransform = _cliArguments.UseBitTransform;
 			bool useOrder = _cliArguments.UseOrder;
@@ -112,7 +104,14 @@ internal static class Program
 				testPrimeCandidateLimit = Math.Max(1, threadCount) * 3;
 			}
 
-			_byDivisorStartPrime = useByDivisor && startPrimeProvided ? currentP : 0UL;
+			if (useByDivisor)
+			{
+				_byDivisorStartPrime = startPrimeProvided ? currentP : 0UL;
+			}
+			else
+			{
+				_byDivisorStartPrime = 0UL;
+			}
 
 			if (useByDivisor && !testMode && string.IsNullOrEmpty(filterFile))
 			{
@@ -120,6 +119,9 @@ internal static class Program
 				return;
 			}
 
+			// Apply GPU prime sieve runtime configuration
+			GpuPrimeWorkLimiter.SetLimit(gpuPrimeThreads);
+			PrimeTester.GpuBatchSize = Math.Max(1, gpuPrimeBatch);
 
 			MersenneDivisorCycles mersenneDivisorCycles = new();
 			if (!File.Exists(cyclesPath) || continueCyclesGeneration)
@@ -175,10 +177,13 @@ internal static class Program
 
 			Console.WriteLine("Divisor cycles are ready");
 
-			blockSize = useByDivisor ? 1 : blockSize;
+			if (useByDivisor)
+			{
+				blockSize = 1;
+			}
 
 			CandidatesCalculator.Initialize(currentP);
-			// PrimeTesters = new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true);
+			PrimeTesters = new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true);
 			// Note: --primes-device controls default device for library kernels; p primality remains CPU here.
 			// Initialize per-thread p residue tracker (Identity model) at currentP
 			if (!useDivisor && !_cliArguments.UseByDivisor)
@@ -261,7 +266,7 @@ internal static class Program
 			orderWarmupLimitOverride ?? 5_000_000UL,
 			NttGpuMath.ReductionMode,
 			mersenneOnGpu ? "gpu" : "cpu",
-			_runPrimesOnCpu ? "cpu" : "gpu",
+			GpuContextPool.ForceCpu ? "cpu" : "gpu",
 			orderOnGpu ? "gpu" : "cpu");
 
 			if (!string.IsNullOrEmpty(_cliArguments.ResultsPrefix))
@@ -422,7 +427,7 @@ internal static class Program
 						_byDivisorStartPrime,
 						static () => _lastCompositeP = true,
 						static () => _lastCompositeP = false,
-						static (candidate, searchedMersenne, detailedCheck, passedAllTests, divisor) => CalculationResultHandler.HandleResult(candidate, divisor, searchedMersenne, detailedCheck, passedAllTests, _lastCompositeP),
+						static (candidate, searchedMersenne, detailedCheck, passedAllTests) => CalculationResultHandler.HandleResult(candidate, searchedMersenne, detailedCheck, passedAllTests, _lastCompositeP),
 						threadCount,
 						byDivisorPrimeRange);
 						
@@ -483,7 +488,7 @@ internal static class Program
 							{
 								p = buffer[j];
 								passedAllTests = IsEvenPerfectCandidate(p, divisorCyclesSearchLimit, out searchedMersenne, out detailedCheck);
-								CalculationResultHandler.HandleResult(p, 0UL, searchedMersenne, detailedCheck, passedAllTests, _lastCompositeP);
+								CalculationResultHandler.HandleResult(p, searchedMersenne, detailedCheck, passedAllTests, _lastCompositeP);
 							}
 
 							continue;
@@ -506,7 +511,7 @@ internal static class Program
 							}
 
 							passedAllTests = IsEvenPerfectCandidate(p, divisorCyclesSearchLimit, out searchedMersenne, out detailedCheck);
-							CalculationResultHandler.HandleResult(p, 0UL, searchedMersenne, detailedCheck, passedAllTests, _lastCompositeP);
+							CalculationResultHandler.HandleResult(p, searchedMersenne, detailedCheck, passedAllTests, _lastCompositeP);
 
 							if (p == maxP)
 							{
@@ -626,9 +631,9 @@ internal static class Program
 		// If primes-device=gpu, route p primality through GPU-assisted sieve with deterministic MR validation.
 		if (!_cliArguments.UseByDivisor)
 		{
-			if (!(_runPrimesOnCpu
-					? PrimeTester.IsPrime(p)
-					: HeuristicCombinedPrimeTester.IsPrimeGpu(p)))
+			if (!(GpuContextPool.ForceCpu
+											? PrimeTesters.Value!.IsPrime(p, CancellationToken.None)
+											: PrimeTesters.Value!.IsPrimeGpu(p, CancellationToken.None)))
 			{
 				_lastCompositeP = true;
 				return false;
@@ -649,7 +654,7 @@ internal static class Program
 		if (_cliArguments.UseByDivisor)
 		{
 			// Windowed pow2mod kernel handles by-divisor scans.
-			return _byDivisorTester!.IsPrime(p, out detailedCheck, out _);
+			return _byDivisorTester!.IsPrime(p, out detailedCheck);
 		}
 
 		detailedCheck = MersenneTesters.Value!.IsMersennePrime(p);

EvenPerfectBitScanner/Utf8CliParser.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Buffers;
 using System.Buffers.Text;
 using System.Text;

PerfectNumbers.Core.Tests/Gpu/GpuContextPoolTests.cs

@@ -1,3 +1,7 @@
+using FluentAssertions;
+using ILGPU;
+using ILGPU.Runtime;
+using PerfectNumbers.Core.Gpu;
 using Xunit;
 
 namespace PerfectNumbers.Core.Tests.Gpu;
@@ -5,88 +9,88 @@ namespace PerfectNumbers.Core.Tests.Gpu;
 [Collection("GpuNtt")]
 public class GpuContextPoolTests
 {
-    // [Fact]
-    // [Trait("Category", "Fast")]
-    // public void RentPreferred_cpu_returns_cpu_accelerator()
-    // {
-    //     GpuContextPool.DisposeAll();
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void RentPreferred_cpu_returns_cpu_accelerator()
+    {
+        GpuContextPool.DisposeAll();
 
-    //     GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         lease.Accelerator.AcceleratorType.Should().Be(AcceleratorType.CPU);
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
+        GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            lease.Accelerator.AcceleratorType.Should().Be(AcceleratorType.CPU);
+        }
+        finally
+        {
+            lease.Dispose();
+        }
 
-    //     GpuContextPool.DisposeAll();
-    // }
+        GpuContextPool.DisposeAll();
+    }
 
-    // [Fact]
-    // [Trait("Category", "Fast")]
-    // public void RentPreferred_reuses_cpu_context()
-    // {
-    //     GpuContextPool.DisposeAll();
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void RentPreferred_reuses_cpu_context()
+    {
+        GpuContextPool.DisposeAll();
 
-    //     Context firstContext;
-    //     Accelerator firstAccelerator;
-    //     GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         firstContext = lease.Context;
-    //         firstAccelerator = lease.Accelerator;
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
+        Context firstContext;
+        Accelerator firstAccelerator;
+        GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            firstContext = lease.Context;
+            firstAccelerator = lease.Accelerator;
+        }
+        finally
+        {
+            lease.Dispose();
+        }
 
-    //     lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         lease.Context.Should().BeSameAs(firstContext);
-    //         lease.Accelerator.Should().BeSameAs(firstAccelerator);
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
+        lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            lease.Context.Should().BeSameAs(firstContext);
+            lease.Accelerator.Should().BeSameAs(firstAccelerator);
+        }
+        finally
+        {
+            lease.Dispose();
+        }
 
-    //     GpuContextPool.DisposeAll();
-    // }
+        GpuContextPool.DisposeAll();
+    }
 
-    // [Fact]
-    // [Trait("Category", "Fast")]
-    // public void DisposeAll_clears_pooled_contexts()
-    // {
-    //     GpuContextPool.DisposeAll();
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void DisposeAll_clears_pooled_contexts()
+    {
+        GpuContextPool.DisposeAll();
 
-    //     Context firstContext;
-    //     GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         firstContext = lease.Context;
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
+        Context firstContext;
+        GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            firstContext = lease.Context;
+        }
+        finally
+        {
+            lease.Dispose();
+        }
 
-    //     GpuContextPool.DisposeAll();
+        GpuContextPool.DisposeAll();
 
-    //     lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         lease.Context.Should().NotBeSameAs(firstContext);
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
+        lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            lease.Context.Should().NotBeSameAs(firstContext);
+        }
+        finally
+        {
+            lease.Dispose();
+        }
 
-    //     GpuContextPool.DisposeAll();
-    // }
+        GpuContextPool.DisposeAll();
+    }
 }
 

PerfectNumbers.Core.Tests/Gpu/GpuKernelCompilationTests.cs

@@ -1,8 +1,8 @@
 using System.Reflection;
+using FluentAssertions;
 using ILGPU;
 using ILGPU.Runtime;
 using PerfectNumbers.Core.Gpu;
-using PerfectNumbers.Core.Gpu.Accelerators;
 using Xunit;
 
 namespace PerfectNumbers.Core.Tests.Gpu;
@@ -114,10 +114,14 @@ public class GpuKernelCompilationTests
         typeof(PrimeOrderGpuHeuristics).GetMethod("GetPow2ModKernel", BindingFlags.NonPublic | BindingFlags.Static)
         ?? throw new InvalidOperationException("PrimeOrderGpuHeuristics.GetPow2ModKernel not found.");
 
+    private static readonly MethodInfo PrimeOrderGetPow2ModWideKernelMethod =
+        typeof(PrimeOrderGpuHeuristics).GetMethod("GetPow2ModWideKernel", BindingFlags.NonPublic | BindingFlags.Static)
+        ?? throw new InvalidOperationException("PrimeOrderGpuHeuristics.GetPow2ModWideKernel not found.");
+
     private static readonly Action<Index1D, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> MersenneDivisorCyclesKernel =
         DivisorCycleKernels.GpuDivisorCycleKernel;
 
-    private static readonly Action<Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>> PrimeTesterSmallPrimeKernel =
+    private static readonly Action<Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<byte>> PrimeTesterSmallPrimeKernel =
         PrimeTesterKernels.SmallPrimeSieveKernel;
 
     private static readonly Action<Index1D, ArrayView<ulong>, ArrayView<byte>> PrimeTesterSharesFactorKernel =
@@ -163,23 +167,23 @@ public class GpuKernelCompilationTests
         return new object[] { name, loader };
     }
 
-    // [Theory]
-    // [Trait("Category", "Fast")]
-    // [MemberData(nameof(KernelLoaders))]
-    // public void Kernel_compiles_without_internal_compiler_errors(string name, Action<Accelerator> compile)
-    // {
-    //     GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         var accelerator = lease.Accelerator;
-    //         Action action = () => compile(accelerator);
-    //         action.Should().NotThrow($"kernel {name} should compile");
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
-    // }
+    [Theory]
+    [Trait("Category", "Fast")]
+    [MemberData(nameof(KernelLoaders))]
+    public void Kernel_compiles_without_internal_compiler_errors(string name, Action<Accelerator> compile)
+    {
+        GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            var accelerator = lease.Accelerator;
+            Action action = () => compile(accelerator);
+            action.Should().NotThrow($"kernel {name} should compile");
+        }
+        finally
+        {
+            lease.Dispose();
+        }
+    }
 
     private static void CompileDivisorCycleCacheKernel(Accelerator accelerator)
     {
@@ -321,67 +325,56 @@ public class GpuKernelCompilationTests
 
     private static void CompilePrimeOrderPow2ModWideKernel(Accelerator accelerator)
     {
-        var kernel = accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>>(PrimeOrderGpuHeuristics.Pow2ModKernelWide);
-        _ = kernel;
+        _ = PrimeOrderGetPow2ModWideKernelMethod.Invoke(null, new object[] { accelerator });
     }
 
     private static void CompileMersenneDivisorCyclesKernel(Accelerator accelerator)
     {
-        var kernel = accelerator.LoadAutoGroupedStreamKernel(MersenneDivisorCyclesKernel);
+        var kernel = accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(MersenneDivisorCyclesKernel);
         _ = kernel;
     }
 
     private static void CompilePrimeTesterSmallPrimeKernel(Accelerator accelerator)
     {
-        var kernel = accelerator.LoadAutoGroupedStreamKernel(PrimeTesterSmallPrimeKernel);
+        var kernel = accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<byte>>(PrimeTesterSmallPrimeKernel);
         _ = kernel;
     }
 
     private static void CompilePrimeTesterSharesFactorKernel(Accelerator accelerator)
     {
-        var kernel = accelerator.LoadAutoGroupedStreamKernel(PrimeTesterSharesFactorKernel);
+        var kernel = accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<byte>>(PrimeTesterSharesFactorKernel);
         _ = kernel;
     }
 
-	private static KernelType _kernelType = KernelType.Pow2ModKernelScan | KernelType.OrderKernelScan | KernelType.IncrementalKernelScan | KernelType.IncrementalOrderKernelScan | KernelType.Pow2ModOrderKernelScan;
-	private static void CompileGpuKernelPoolKernels(Accelerator accelerator)
-	{
+    private static void CompileGpuKernelPoolKernels(Accelerator accelerator)
+    {
+        _ = accelerator;
+        var lease = GpuKernelPool.GetKernel(useGpuOrder: false);
+        try
+        {
+            _ = lease.OrderKernel;
+            _ = lease.IncrementalKernel;
+            _ = lease.Pow2ModKernel;
+            _ = lease.IncrementalOrderKernel;
+            _ = lease.Pow2ModOrderKernel;
+        }
+        finally
+        {
+            lease.Dispose();
+        }
 
-		GpuPrimeWorkLimiter.Acquire();
-		int acceleratorIndex = AcceleratorPool.Shared.Rent();
-		AcceleratorStream stream = AcceleratorStreamPool.Rent(acceleratorIndex);
-		try
-		{
-			var kernels = GpuKernelPool.GetOrAddKernels(acceleratorIndex, stream, _kernelType);
-			_ = kernels.Order;
-			_ = kernels.Incremental;
-			_ = kernels.Pow2Mod;
-			_ = kernels.IncrementalOrder;
-			_ = kernels.Pow2ModOrder;
-		}
-		finally
-		{
-			stream.Synchronize();
-			AcceleratorStreamPool.Return(acceleratorIndex, stream);
-			// GpuPrimeWorkLimiter.Release();
-		}
-
-		stream = AcceleratorStreamPool.Rent(acceleratorIndex);
-		GpuPrimeWorkLimiter.Acquire();
-		try
-		{
-			var kernels = GpuKernelPool.GetOrAddKernels(acceleratorIndex, stream, _kernelType);
-			_ = kernels.Order;
-			_ = kernels.Incremental;
-			_ = kernels.Pow2Mod;
-			_ = kernels.IncrementalOrder;
-			_ = kernels.Pow2ModOrder;
-		}
-		finally
-		{
-			stream.Synchronize();
-			AcceleratorStreamPool.Return(acceleratorIndex, stream);
-			// GpuPrimeWorkLimiter.Release();
-		}
-	}
+        var orderLease = GpuKernelPool.GetKernel(useGpuOrder: true);
+        try
+        {
+            _ = orderLease.OrderKernel;
+            _ = orderLease.IncrementalKernel;
+            _ = orderLease.Pow2ModKernel;
+            _ = orderLease.IncrementalOrderKernel;
+            _ = orderLease.Pow2ModOrderKernel;
+        }
+        finally
+        {
+            orderLease.Dispose();
+        }
+    }
 }

PerfectNumbers.Core.Tests/Gpu/GpuPrimeLimiterTests.cs

@@ -18,33 +18,22 @@ public class GpuPrimeLimiterTests
         var startedSecond = new TaskCompletionSource<bool>();
         var sw = new Stopwatch();
 
-        GpuPrimeWorkLimiter.Acquire();
+        using var first = GpuPrimeWorkLimiter.Acquire();
         sw.Start();
 
         var secondTask = Task.Run(() =>
         {
-            GpuPrimeWorkLimiter.Acquire();
-            try
-            {
-                startedSecond.TrySetResult(true);
-            }
-            finally
-            {
-				GpuPrimeWorkLimiter.Release();
-            }
+            using var second = GpuPrimeWorkLimiter.Acquire();
+            startedSecond.TrySetResult(true);
         });
 
-        try
-        {
-            // Give secondTask a moment to attempt acquire (it should block).
-            await Task.Delay(50);
-            startedSecond.Task.IsCompleted.Should().BeFalse();
-        }
-        finally
-        {
-            // Release first after the initial wait so the second task can proceed.
-			GpuPrimeWorkLimiter.Release();
-        }
+        // Give secondTask a moment to attempt acquire (it should block).
+        await Task.Delay(50);
+        startedSecond.Task.IsCompleted.Should().BeFalse();
+
+        // Release first after short delay, allowing second to continue.
+        // (Dispose at scope end, but we want to end now.)
+        first.Dispose();
 
         await secondTask.WaitAsync(TimeSpan.FromSeconds(1));
         sw.Stop();

PerfectNumbers.Core.Tests/Gpu/LucasLehmerPrimeTesterTests.cs

@@ -14,7 +14,7 @@ public class LucasLehmerPrimeTesterTests
     [Trait("Category", "Fast")]
     public void IsMersennePrime_gpu_returns_expected_results(ulong p, bool expected)
     {
-        new MersenneNumberLucasLehmerGpuTester().IsPrime(p, true).Should().Be(expected);
+        new MersenneNumberLucasLehmerGpuTester().IsMersennePrime(p).Should().Be(expected);
     }
 
     [Fact]
@@ -26,7 +26,7 @@ public class LucasLehmerPrimeTesterTests
         const ulong exponent = 128UL;
         var tester = new MersenneNumberLucasLehmerGpuTester();
         tester.WarmUpNttParameters(exponent);
-        tester.IsPrime(exponent, true).Should().BeFalse();
+        tester.IsMersennePrime(exponent).Should().BeFalse();
     }
 
     [Fact]
@@ -49,7 +49,7 @@ public class LucasLehmerPrimeTesterTests
     {
         var tester = new MersenneNumberLucasLehmerGpuTester();
         tester.WarmUpNttParameters(exponent);
-        tester.IsPrime(exponent, true).Should().BeFalse();
+        tester.IsMersennePrime(exponent).Should().BeFalse();
     }
 
     [Theory]

PerfectNumbers.Core.Tests/Gpu/NttGpuMathTests.cs

@@ -13,352 +13,367 @@ namespace PerfectNumbers.Core.Tests.Gpu;
 [Collection("GpuNtt")]
 public class NttGpuMathTests
 {
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void ForwardGpu_reference_matches_cpu_forward()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Reference;
-			Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
-			cpu[0] = new GpuUInt128(0UL, 1UL);
-			cpu[1] = new GpuUInt128(0UL, 2UL);
-			cpu[2] = new GpuUInt128(0UL, 3UL);
-			cpu[3] = new GpuUInt128(0UL, 4UL);
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
-			cpu.CopyTo(gpu);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			NttGpuMath.Forward(cpu, modulus, primitiveRoot);
-			NttGpuMath.ForwardGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < cpu.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void ForwardGpu_reference_matches_cpu_forward()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Reference;
+            Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
+            cpu[0] = new GpuUInt128(0UL, 1UL);
+            cpu[1] = new GpuUInt128(0UL, 2UL);
+            cpu[2] = new GpuUInt128(0UL, 3UL);
+            cpu[3] = new GpuUInt128(0UL, 4UL);
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
+            cpu.CopyTo(gpu);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            NttGpuMath.Forward(cpu, modulus, primitiveRoot);
+            NttGpuMath.ForwardGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < cpu.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void ForwardGpu_staged_matches_cpu_forward()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Staged;
-			Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
-			cpu[0] = new GpuUInt128(0UL, 1UL);
-			cpu[1] = new GpuUInt128(0UL, 2UL);
-			cpu[2] = new GpuUInt128(0UL, 3UL);
-			cpu[3] = new GpuUInt128(0UL, 4UL);
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
-			cpu.CopyTo(gpu);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			NttGpuMath.Forward(cpu, modulus, primitiveRoot);
-			NttGpuMath.ForwardGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < cpu.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void ForwardGpu_staged_matches_cpu_forward()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Staged;
+            Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
+            cpu[0] = new GpuUInt128(0UL, 1UL);
+            cpu[1] = new GpuUInt128(0UL, 2UL);
+            cpu[2] = new GpuUInt128(0UL, 3UL);
+            cpu[3] = new GpuUInt128(0UL, 4UL);
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
+            cpu.CopyTo(gpu);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            NttGpuMath.Forward(cpu, modulus, primitiveRoot);
+            NttGpuMath.ForwardGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < cpu.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void InverseGpu_reference_matches_cpu_inverse()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Reference;
-			Span<GpuUInt128> input = stackalloc GpuUInt128[4];
-			input[0] = new GpuUInt128(0UL, 5UL);
-			input[1] = new GpuUInt128(0UL, 7UL);
-			input[2] = new GpuUInt128(0UL, 9UL);
-			input[3] = new GpuUInt128(0UL, 11UL);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			Span<GpuUInt128> transformed = stackalloc GpuUInt128[4];
-			input.CopyTo(transformed);
-			NttGpuMath.Forward(transformed, modulus, primitiveRoot);
-			Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
-			transformed.CopyTo(cpu);
-			NttGpuMath.Inverse(cpu, modulus, primitiveRoot);
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
-			transformed.CopyTo(gpu);
-			NttGpuMath.InverseGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < input.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void InverseGpu_reference_matches_cpu_inverse()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Reference;
+            Span<GpuUInt128> input = stackalloc GpuUInt128[4];
+            input[0] = new GpuUInt128(0UL, 5UL);
+            input[1] = new GpuUInt128(0UL, 7UL);
+            input[2] = new GpuUInt128(0UL, 9UL);
+            input[3] = new GpuUInt128(0UL, 11UL);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            Span<GpuUInt128> transformed = stackalloc GpuUInt128[4];
+            input.CopyTo(transformed);
+            NttGpuMath.Forward(transformed, modulus, primitiveRoot);
+            Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
+            transformed.CopyTo(cpu);
+            NttGpuMath.Inverse(cpu, modulus, primitiveRoot);
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
+            transformed.CopyTo(gpu);
+            NttGpuMath.InverseGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < input.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void InverseGpu_staged_matches_cpu_inverse()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Staged;
-			Span<GpuUInt128> input = stackalloc GpuUInt128[4];
-			input[0] = new GpuUInt128(0UL, 5UL);
-			input[1] = new GpuUInt128(0UL, 7UL);
-			input[2] = new GpuUInt128(0UL, 9UL);
-			input[3] = new GpuUInt128(0UL, 11UL);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			Span<GpuUInt128> transformed = stackalloc GpuUInt128[4];
-			input.CopyTo(transformed);
-			NttGpuMath.Forward(transformed, modulus, primitiveRoot);
-			Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
-			transformed.CopyTo(cpu);
-			NttGpuMath.Inverse(cpu, modulus, primitiveRoot);
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
-			transformed.CopyTo(gpu);
-			NttGpuMath.InverseGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < input.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void InverseGpu_staged_matches_cpu_inverse()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Staged;
+            Span<GpuUInt128> input = stackalloc GpuUInt128[4];
+            input[0] = new GpuUInt128(0UL, 5UL);
+            input[1] = new GpuUInt128(0UL, 7UL);
+            input[2] = new GpuUInt128(0UL, 9UL);
+            input[3] = new GpuUInt128(0UL, 11UL);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            Span<GpuUInt128> transformed = stackalloc GpuUInt128[4];
+            input.CopyTo(transformed);
+            NttGpuMath.Forward(transformed, modulus, primitiveRoot);
+            Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
+            transformed.CopyTo(cpu);
+            NttGpuMath.Inverse(cpu, modulus, primitiveRoot);
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
+            transformed.CopyTo(gpu);
+            NttGpuMath.InverseGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < input.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void Montgomery_twiddle_inverses_multiply_to_r2()
-	{
-		var modulus = new GpuUInt128(0UL, 17UL);
-		var primitiveRoot = new GpuUInt128(0UL, 3UL);
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void Montgomery_twiddle_inverses_multiply_to_r2()
+    {
+        var modulus = new GpuUInt128(0UL, 17UL);
+        var primitiveRoot = new GpuUInt128(0UL, 3UL);
 
-		var accelerator = SharedGpuContext.CreateAccelerator();
-		var stream = accelerator.CreateStream();
+        GpuContextPool.GpuContextLease gpu = GpuContextPool.Rent();
+        try
+        {
+            var accelerator = gpu.Accelerator;
 
-		var method = typeof(NttGpuMath).GetMethod("GetSquareCache", BindingFlags.NonPublic | BindingFlags.Static);
-		method.Should().NotBeNull();
-		var cache = method!.Invoke(null, new object[] { accelerator, 8, modulus, primitiveRoot })!;
-		var cacheType = cache.GetType();
+            var method = typeof(NttGpuMath).GetMethod("GetSquareCache", BindingFlags.NonPublic | BindingFlags.Static);
+            method.Should().NotBeNull();
+            var cache = method!.Invoke(null, new object[] { accelerator, 8, modulus, primitiveRoot })!;
+            var cacheType = cache.GetType();
 
-		var twiddlesMont = (MemoryBuffer1D<GpuUInt128, Stride1D.Dense>)cacheType.GetProperty("TwiddlesMont")!.GetValue(cache)!;
-		var twiddlesInvMont = (MemoryBuffer1D<GpuUInt128, Stride1D.Dense>)cacheType.GetProperty("TwiddlesInvMont")!.GetValue(cache)!;
-		var r2 = (ulong)cacheType.GetProperty("MontR2Mod64")!.GetValue(cache)!;
-		var mod = (ulong)cacheType.GetProperty("ModulusLow")!.GetValue(cache)!;
+            var twiddlesMont = (MemoryBuffer1D<GpuUInt128, Stride1D.Dense>)cacheType.GetProperty("TwiddlesMont")!.GetValue(cache)!;
+            var twiddlesInvMont = (MemoryBuffer1D<GpuUInt128, Stride1D.Dense>)cacheType.GetProperty("TwiddlesInvMont")!.GetValue(cache)!;
+            var r2 = (ulong)cacheType.GetProperty("MontR2Mod64")!.GetValue(cache)!;
+            var mod = (ulong)cacheType.GetProperty("ModulusLow")!.GetValue(cache)!;
 
-		int count = 7; // length 8 -> 7 twiddles
-		var forward = new GpuUInt128[count];
-		var inverse = new GpuUInt128[count];
-		twiddlesMont.CopyToCPU(stream, forward);
-		twiddlesInvMont.CopyToCPU(stream, inverse);
-		stream.Synchronize();
-		stream.Dispose();
-		accelerator.Dispose();
+            int count = 7; // length 8 -> 7 twiddles
+            var forward = new GpuUInt128[count];
+            var inverse = new GpuUInt128[count];
+            twiddlesMont.CopyToCPU(forward);
+            twiddlesInvMont.CopyToCPU(inverse);
 
-		for (int i = 0; i < count; i++)
-		{
-			ulong prod = (ulong)((((BigInteger)forward[i].Low) * inverse[i].Low) % mod);
-			prod.Should().Be(r2);
-		}
-	}
+            for (int i = 0; i < count; i++)
+            {
+                ulong prod = (ulong)((((BigInteger)forward[i].Low) * inverse[i].Low) % mod);
+                prod.Should().Be(r2);
+            }
+        }
+        finally
+        {
+            gpu.Dispose();
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void ConvolveGpu_reference_matches_cpu_convolve()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Reference;
-			Span<GpuUInt128> leftCpu = stackalloc GpuUInt128[4];
-			Span<GpuUInt128> rightCpu = stackalloc GpuUInt128[4];
-			leftCpu[0] = new GpuUInt128(0UL, 1UL);
-			leftCpu[1] = new GpuUInt128(0UL, 2UL);
-			leftCpu[2] = new GpuUInt128(0UL, 3UL);
-			leftCpu[3] = new GpuUInt128(0UL, 4UL);
-			rightCpu[0] = new GpuUInt128(0UL, 5UL);
-			rightCpu[1] = new GpuUInt128(0UL, 6UL);
-			rightCpu[2] = new GpuUInt128(0UL, 7UL);
-			rightCpu[3] = new GpuUInt128(0UL, 8UL);
-			Span<GpuUInt128> leftGpu = stackalloc GpuUInt128[4];
-			Span<GpuUInt128> rightGpu = stackalloc GpuUInt128[4];
-			leftCpu.CopyTo(leftGpu);
-			rightCpu.CopyTo(rightGpu);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			NttGpuMath.Convolve(leftCpu, rightCpu, modulus, primitiveRoot);
-			NttGpuMath.ConvolveGpu(leftGpu, rightGpu, modulus, primitiveRoot);
-			for (int i = 0; i < leftCpu.Length; i++)
-			{
-				leftGpu[i].Should().Be(leftCpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void ConvolveGpu_reference_matches_cpu_convolve()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Reference;
+            Span<GpuUInt128> leftCpu = stackalloc GpuUInt128[4];
+            Span<GpuUInt128> rightCpu = stackalloc GpuUInt128[4];
+            leftCpu[0] = new GpuUInt128(0UL, 1UL);
+            leftCpu[1] = new GpuUInt128(0UL, 2UL);
+            leftCpu[2] = new GpuUInt128(0UL, 3UL);
+            leftCpu[3] = new GpuUInt128(0UL, 4UL);
+            rightCpu[0] = new GpuUInt128(0UL, 5UL);
+            rightCpu[1] = new GpuUInt128(0UL, 6UL);
+            rightCpu[2] = new GpuUInt128(0UL, 7UL);
+            rightCpu[3] = new GpuUInt128(0UL, 8UL);
+            Span<GpuUInt128> leftGpu = stackalloc GpuUInt128[4];
+            Span<GpuUInt128> rightGpu = stackalloc GpuUInt128[4];
+            leftCpu.CopyTo(leftGpu);
+            rightCpu.CopyTo(rightGpu);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            NttGpuMath.Convolve(leftCpu, rightCpu, modulus, primitiveRoot);
+            NttGpuMath.ConvolveGpu(leftGpu, rightGpu, modulus, primitiveRoot);
+            for (int i = 0; i < leftCpu.Length; i++)
+            {
+                leftGpu[i].Should().Be(leftCpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void ConvolveGpu_staged_matches_cpu_convolve()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Staged;
-			Span<GpuUInt128> leftCpu = stackalloc GpuUInt128[4];
-			Span<GpuUInt128> rightCpu = stackalloc GpuUInt128[4];
-			leftCpu[0] = new GpuUInt128(0UL, 1UL);
-			leftCpu[1] = new GpuUInt128(0UL, 2UL);
-			leftCpu[2] = new GpuUInt128(0UL, 3UL);
-			leftCpu[3] = new GpuUInt128(0UL, 4UL);
-			rightCpu[0] = new GpuUInt128(0UL, 5UL);
-			rightCpu[1] = new GpuUInt128(0UL, 6UL);
-			rightCpu[2] = new GpuUInt128(0UL, 7UL);
-			rightCpu[3] = new GpuUInt128(0UL, 8UL);
-			Span<GpuUInt128> leftGpu = stackalloc GpuUInt128[4];
-			Span<GpuUInt128> rightGpu = stackalloc GpuUInt128[4];
-			leftCpu.CopyTo(leftGpu);
-			rightCpu.CopyTo(rightGpu);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			NttGpuMath.Convolve(leftCpu, rightCpu, modulus, primitiveRoot);
-			NttGpuMath.ConvolveGpu(leftGpu, rightGpu, modulus, primitiveRoot);
-			for (int i = 0; i < leftCpu.Length; i++)
-			{
-				leftGpu[i].Should().Be(leftCpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void ConvolveGpu_staged_matches_cpu_convolve()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Staged;
+            Span<GpuUInt128> leftCpu = stackalloc GpuUInt128[4];
+            Span<GpuUInt128> rightCpu = stackalloc GpuUInt128[4];
+            leftCpu[0] = new GpuUInt128(0UL, 1UL);
+            leftCpu[1] = new GpuUInt128(0UL, 2UL);
+            leftCpu[2] = new GpuUInt128(0UL, 3UL);
+            leftCpu[3] = new GpuUInt128(0UL, 4UL);
+            rightCpu[0] = new GpuUInt128(0UL, 5UL);
+            rightCpu[1] = new GpuUInt128(0UL, 6UL);
+            rightCpu[2] = new GpuUInt128(0UL, 7UL);
+            rightCpu[3] = new GpuUInt128(0UL, 8UL);
+            Span<GpuUInt128> leftGpu = stackalloc GpuUInt128[4];
+            Span<GpuUInt128> rightGpu = stackalloc GpuUInt128[4];
+            leftCpu.CopyTo(leftGpu);
+            rightCpu.CopyTo(rightGpu);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            NttGpuMath.Convolve(leftCpu, rightCpu, modulus, primitiveRoot);
+            NttGpuMath.ConvolveGpu(leftGpu, rightGpu, modulus, primitiveRoot);
+            for (int i = 0; i < leftCpu.Length; i++)
+            {
+                leftGpu[i].Should().Be(leftCpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void SquareGpu_reference_matches_cpu_square()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Reference;
-			Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
-			cpu[0] = new GpuUInt128(0UL, 1UL);
-			cpu[1] = new GpuUInt128(0UL, 2UL);
-			cpu[2] = new GpuUInt128(0UL, 3UL);
-			cpu[3] = new GpuUInt128(0UL, 4UL);
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
-			cpu.CopyTo(gpu);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			NttGpuMath.Square(cpu, modulus, primitiveRoot);
-			NttGpuMath.SquareGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < cpu.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void SquareGpu_reference_matches_cpu_square()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Reference;
+            Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
+            cpu[0] = new GpuUInt128(0UL, 1UL);
+            cpu[1] = new GpuUInt128(0UL, 2UL);
+            cpu[2] = new GpuUInt128(0UL, 3UL);
+            cpu[3] = new GpuUInt128(0UL, 4UL);
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
+            cpu.CopyTo(gpu);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            NttGpuMath.Square(cpu, modulus, primitiveRoot);
+            NttGpuMath.SquareGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < cpu.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void SquareGpu_staged_matches_cpu_square()
-	{
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Staged;
-			Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
-			cpu[0] = new GpuUInt128(0UL, 1UL);
-			cpu[1] = new GpuUInt128(0UL, 2UL);
-			cpu[2] = new GpuUInt128(0UL, 3UL);
-			cpu[3] = new GpuUInt128(0UL, 4UL);
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
-			cpu.CopyTo(gpu);
-			var modulus = new GpuUInt128(0UL, 17UL);
-			var primitiveRoot = new GpuUInt128(0UL, 3UL);
-			NttGpuMath.Square(cpu, modulus, primitiveRoot);
-			NttGpuMath.SquareGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < cpu.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void SquareGpu_staged_matches_cpu_square()
+    {
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Staged;
+            Span<GpuUInt128> cpu = stackalloc GpuUInt128[4];
+            cpu[0] = new GpuUInt128(0UL, 1UL);
+            cpu[1] = new GpuUInt128(0UL, 2UL);
+            cpu[2] = new GpuUInt128(0UL, 3UL);
+            cpu[3] = new GpuUInt128(0UL, 4UL);
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[4];
+            cpu.CopyTo(gpu);
+            var modulus = new GpuUInt128(0UL, 17UL);
+            var primitiveRoot = new GpuUInt128(0UL, 3UL);
+            NttGpuMath.Square(cpu, modulus, primitiveRoot);
+            NttGpuMath.SquareGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < cpu.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void BitReverseGpu_matches_cpu()
-	{
-		GpuUInt128[] cpu = new GpuUInt128[8];
-		for (ulong i = 0; i < (ulong)cpu.Length; i++)
-		{
-			cpu[i] = new GpuUInt128(0UL, i);
-		}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void BitReverseGpu_matches_cpu()
+    {
+        GpuUInt128[] cpu = new GpuUInt128[8];
+        for (ulong i = 0; i < (ulong)cpu.Length; i++)
+        {
+            cpu[i] = new GpuUInt128(0UL, i);
+        }
 
-		GpuUInt128[] gpu = (GpuUInt128[])cpu.Clone();
-		NttGpuMath.BitReverse(cpu);
-		NttGpuMath.BitReverseGpu(gpu);
-		gpu.Should().Equal(cpu);
-	}
+        GpuUInt128[] gpu = (GpuUInt128[])cpu.Clone();
+        NttGpuMath.BitReverse(cpu);
+        NttGpuMath.BitReverseGpu(gpu);
+        gpu.Should().Equal(cpu);
+    }
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void DisposeAll_clears_ntt_caches()
-	{
-		// Ensure the cache starts empty.
-		NttGpuMath.ClearCaches();
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void DisposeAll_clears_ntt_caches()
+    {
+        // Ensure the cache starts empty.
+        NttGpuMath.ClearCaches();
 
-		Span<GpuUInt128> values = stackalloc GpuUInt128[2];
-		values[0] = new GpuUInt128(0UL, 1UL);
-		values[1] = new GpuUInt128(0UL, 2UL);
-		var modulus = new GpuUInt128(0UL, 17UL);
-		var primitiveRoot = new GpuUInt128(0UL, 3UL);
-		Accelerator accelerator = SharedGpuContext.CreateAccelerator();
-		var stream = accelerator.CreateStream();
-		var buffer = accelerator.Allocate1D<GpuUInt128>(values.Length);
-		buffer.View.CopyFromCPU(stream, ref values[0], values.Length);
-		NttGpuMath.SquareDevice(accelerator, stream, buffer.View, modulus, primitiveRoot);
-		stream.Synchronize();
-		stream.Dispose();
-		buffer.Dispose();
-		accelerator.Dispose();
+        Span<GpuUInt128> values = stackalloc GpuUInt128[2];
+        values[0] = new GpuUInt128(0UL, 1UL);
+        values[1] = new GpuUInt128(0UL, 2UL);
+        var modulus = new GpuUInt128(0UL, 17UL);
+        var primitiveRoot = new GpuUInt128(0UL, 3UL);
+        GpuContextPool.GpuContextLease gpu = GpuContextPool.Rent();
+        try
+        {
+            var buffer = gpu.Accelerator.Allocate1D<GpuUInt128>(values.Length);
+            try
+            {
+                buffer.View.CopyFromCPU(ref values[0], values.Length);
+                NttGpuMath.SquareDevice(gpu.Accelerator, buffer.View, modulus, primitiveRoot);
+            }
+            finally
+            {
+                buffer.Dispose();
+            }
+        }
+        finally
+        {
+            gpu.Dispose();
+        }
 
-		// Verify that the square cache now holds entries for the accelerator.
-		var field = typeof(NttGpuMath).GetField("SquareCache", BindingFlags.NonPublic | BindingFlags.Static)!;
-		var cacheObj = field.GetValue(null)!;
-		int count = (int)cacheObj.GetType().GetProperty("Count")!.GetValue(cacheObj)!;
-		count.Should().BeGreaterThan(0);
+        // Verify that the square cache now holds entries for the accelerator.
+        var field = typeof(NttGpuMath).GetField("SquareCache", BindingFlags.NonPublic | BindingFlags.Static)!;
+        var cacheObj = field.GetValue(null)!;
+        int count = (int)cacheObj.GetType().GetProperty("Count")!.GetValue(cacheObj)!;
+        count.Should().BeGreaterThan(0);
 
-		count = (int)cacheObj.GetType().GetProperty("Count")!.GetValue(cacheObj)!;
-		count.Should().Be(0);
-	}
+        GpuContextPool.DisposeAll();
+
+        count = (int)cacheObj.GetType().GetProperty("Count")!.GetValue(cacheObj)!;
+        count.Should().Be(0);
+    }
 }
 

PerfectNumbers.Core.Tests/Gpu/NttMontgomeryTests.cs

@@ -9,83 +9,86 @@ namespace PerfectNumbers.Core.Tests.Gpu;
 [Trait("Category", "Fast")]
 public class NttMontgomeryTests
 {
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void SquareDevice_montgomery64_matches_cpu_square_on_small_input()
-	{
-		// Small 64-bit modulus and tiny input to keep runtime trivial.
-		var modulus = new GpuUInt128(0UL, 17UL);
-		var primitiveRoot = new GpuUInt128(0UL, 3UL);
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void SquareDevice_montgomery64_matches_cpu_square_on_small_input()
+    {
+        // Small 64-bit modulus and tiny input to keep runtime trivial.
+        var modulus = new GpuUInt128(0UL, 17UL);
+        var primitiveRoot = new GpuUInt128(0UL, 3UL);
 
-		Span<GpuUInt128> cpu = stackalloc GpuUInt128[8];
-		for (ulong i = 0; i < (ulong)cpu.Length; i++)
-		{
-			cpu[(int)i] = new GpuUInt128(0UL, i + 1UL);
-		}
-		Span<GpuUInt128> gpu = stackalloc GpuUInt128[16];
-		cpu.CopyTo(gpu);
-		for (int i = cpu.Length; i < gpu.Length; i++)
-		{
-			gpu[i] = new GpuUInt128(0UL, 0UL);
-		}
+        Span<GpuUInt128> cpu = stackalloc GpuUInt128[8];
+        for (ulong i = 0; i < (ulong)cpu.Length; i++)
+        {
+            cpu[(int)i] = new GpuUInt128(0UL, i + 1UL);
+        }
+        Span<GpuUInt128> gpu = stackalloc GpuUInt128[16];
+        cpu.CopyTo(gpu);
+        for (int i = cpu.Length; i < gpu.Length; i++)
+        {
+            gpu[i] = new GpuUInt128(0UL, 0UL);
+        }
 
-		// CPU reference
-		NttGpuMath.Square(cpu, modulus, primitiveRoot);
+        // CPU reference
+        NttGpuMath.Square(cpu, modulus, primitiveRoot);
 
-		// Device execution
-		var accelerator = SharedGpuContext.CreateAccelerator();
-		var stream = accelerator.CreateStream();
-		using var buffer = accelerator.Allocate1D<GpuUInt128>(gpu.Length);
-		buffer.View.CopyFromCPU(stream, ref gpu[0], gpu.Length);
-		NttGpuMath.SquareDevice(accelerator, stream, buffer.View, modulus, primitiveRoot);
-		buffer.View.CopyToCPU(stream, ref gpu[0], gpu.Length);
-		stream.Synchronize();
-		stream.Dispose();
-		accelerator.Dispose();
+        // Device execution
+        GpuContextPool.GpuContextLease context = GpuContextPool.Rent();
+        try
+        {
+            var accelerator = context.Accelerator;
+            using var buffer = accelerator.Allocate1D<GpuUInt128>(gpu.Length);
+            buffer.View.CopyFromCPU(ref gpu[0], gpu.Length);
+            NttGpuMath.SquareDevice(accelerator, buffer.View, modulus, primitiveRoot);
+            buffer.View.CopyToCPU(ref gpu[0], gpu.Length);
 
-		for (int i = 0; i < cpu.Length; i++)
-		{
-			gpu[i].Should().Be(cpu[i]);
-		}
+            for (int i = 0; i < cpu.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            context.Dispose();
+        }
+    }
 
-	}
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void InverseDevice_montgomery64_matches_cpu_inverse_on_small_input()
+    {
+        var modulus = new GpuUInt128(0UL, 17UL);
+        var primitiveRoot = new GpuUInt128(0UL, 3UL);
 
-	[Fact]
-	[Trait("Category", "Fast")]
-	public void InverseDevice_montgomery64_matches_cpu_inverse_on_small_input()
-	{
-		var modulus = new GpuUInt128(0UL, 17UL);
-		var primitiveRoot = new GpuUInt128(0UL, 3UL);
+        Span<GpuUInt128> input = stackalloc GpuUInt128[8];
+        for (ulong i = 0; i < (ulong)input.Length; i++)
+        {
+            input[(int)i] = new GpuUInt128(0UL, i + 1UL);
+        }
 
-		Span<GpuUInt128> input = stackalloc GpuUInt128[8];
-		for (ulong i = 0; i < (ulong)input.Length; i++)
-		{
-			input[(int)i] = new GpuUInt128(0UL, i + 1UL);
-		}
+        Span<GpuUInt128> transformed = stackalloc GpuUInt128[input.Length];
+        input.CopyTo(transformed);
+        NttGpuMath.Forward(transformed, modulus, primitiveRoot);
 
-		Span<GpuUInt128> transformed = stackalloc GpuUInt128[input.Length];
-		input.CopyTo(transformed);
-		NttGpuMath.Forward(transformed, modulus, primitiveRoot);
+        Span<GpuUInt128> cpu = stackalloc GpuUInt128[input.Length];
+        transformed.CopyTo(cpu);
+        NttGpuMath.Inverse(cpu, modulus, primitiveRoot);
 
-		Span<GpuUInt128> cpu = stackalloc GpuUInt128[input.Length];
-		transformed.CopyTo(cpu);
-		NttGpuMath.Inverse(cpu, modulus, primitiveRoot);
-
-		var original = NttGpuMath.GpuTransformBackend;
-		try
-		{
-			NttGpuMath.GpuTransformBackend = NttBackend.Staged;
-			Span<GpuUInt128> gpu = stackalloc GpuUInt128[input.Length];
-			transformed.CopyTo(gpu);
-			NttGpuMath.InverseGpu(gpu, modulus, primitiveRoot);
-			for (int i = 0; i < input.Length; i++)
-			{
-				gpu[i].Should().Be(cpu[i]);
-			}
-		}
-		finally
-		{
-			NttGpuMath.GpuTransformBackend = original;
-		}
-	}
+        var original = NttGpuMath.GpuTransformBackend;
+        try
+        {
+            NttGpuMath.GpuTransformBackend = NttBackend.Staged;
+            Span<GpuUInt128> gpu = stackalloc GpuUInt128[input.Length];
+            transformed.CopyTo(gpu);
+            NttGpuMath.InverseGpu(gpu, modulus, primitiveRoot);
+            for (int i = 0; i < input.Length; i++)
+            {
+                gpu[i].Should().Be(cpu[i]);
+            }
+        }
+        finally
+        {
+            NttGpuMath.GpuTransformBackend = original;
+        }
+    }
 }

PerfectNumbers.Core.Tests/Gpu/PrimeTesterGpuTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core.Gpu;
 using Xunit;
 
 namespace PerfectNumbers.Core.Tests.Gpu;
@@ -9,23 +10,41 @@ public class PrimeTesterGpuTests
     [Fact]
     public void IsPrimeGpu_accepts_known_primes()
     {
-		var tester = new PrimeTester();
-		ulong[] primes = [31UL, 61UL, 89UL, 107UL, 127UL, 521UL];
-		foreach (ulong prime in primes)
-		{
-			PrimeTester.IsPrimeGpu(prime).Should().BeTrue();
-		}
+        GpuContextPool.ForceCpu = false;
+        try
+        {
+            var tester = new PrimeTester();
+            ulong[] primes = [31UL, 61UL, 89UL, 107UL, 127UL, 521UL];
+            foreach (ulong prime in primes)
+            {
+                tester.IsPrimeGpu(prime, CancellationToken.None).Should().BeTrue();
+            }
+        }
+        finally
+        {
+            GpuContextPool.ForceCpu = false;
+            GpuContextPool.DisposeAll();
+        }
     }
 
     [Fact]
     public void IsPrimeGpu_rejects_composites()
     {
-		var tester = new PrimeTester();
-		ulong[] composites = [33UL, 39UL, 51UL, 77UL, 91UL];
-		foreach (ulong composite in composites)
-		{
-			PrimeTester.IsPrimeGpu(composite).Should().BeFalse();
-		}
+        GpuContextPool.ForceCpu = false;
+        try
+        {
+            var tester = new PrimeTester();
+            ulong[] composites = [33UL, 39UL, 51UL, 77UL, 91UL];
+            foreach (ulong composite in composites)
+            {
+                tester.IsPrimeGpu(composite, CancellationToken.None).Should().BeFalse();
+            }
+        }
+        finally
+        {
+            GpuContextPool.ForceCpu = false;
+            GpuContextPool.DisposeAll();
+        }
     }
 
 }

PerfectNumbers.Core.Tests/Gpu/ULongExtensionsGpuTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core;
 using Xunit;
 
 namespace PerfectNumbers.Core.Tests.Gpu;

PerfectNumbers.Core.Tests/GpuKernelPoolTests.cs

@@ -7,26 +7,26 @@ namespace PerfectNumbers.Core.Tests;
 [Collection("GpuNtt")]
 public class GpuKernelPoolTests
 {
-    // [Fact]
-    // [Trait("Category", "Fast")]
-    // public void EnsureSmallCyclesOnDevice_returns_same_view_on_subsequent_calls()
-    // {
-    //     GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
-    //     try
-    //     {
-    //         var accelerator = lease.Accelerator;
+    [Fact]
+    [Trait("Category", "Fast")]
+    public void EnsureSmallCyclesOnDevice_returns_same_view_on_subsequent_calls()
+    {
+        GpuContextPool.GpuContextLease lease = GpuContextPool.RentPreferred(preferCpu: true);
+        try
+        {
+            var accelerator = lease.Accelerator;
 
-    //         var first = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
-    //         var second = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
+            var first = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
+            var second = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
 
-    //         second.Equals(first).Should().BeTrue();
-    //         second.Length.Should().Be(MersenneDivisorCycles.SmallDivisorsMax + 1);
-    //     }
-    //     finally
-    //     {
-    //         lease.Dispose();
-    //     }
-    // }
+            second.Equals(first).Should().BeTrue();
+            second.Length.Should().Be(MersenneDivisorCycles.SmallDivisorsMax + 1);
+        }
+        finally
+        {
+            lease.Dispose();
+        }
+    }
 
     [Fact]
     [Trait("Category", "Fast")]

PerfectNumbers.Core.Tests/GpuWorkLimiterTests.cs

@@ -17,31 +17,19 @@ public class GpuWorkLimiterTests
         var startedSecond = new TaskCompletionSource<bool>();
         var sw = new Stopwatch();
 
-        var first = GpuWorkLimiter.Acquire();
+        using var first = GpuWorkLimiter.Acquire();
         sw.Start();
 
         var secondTask = Task.Run(() =>
         {
-            var second = GpuWorkLimiter.Acquire();
-            try
-            {
-                startedSecond.TrySetResult(true);
-            }
-            finally
-            {
-                second.Dispose();
-            }
+            using var second = GpuWorkLimiter.Acquire();
+            startedSecond.TrySetResult(true);
         });
 
-        try
-        {
-            await Task.Delay(50);
-            startedSecond.Task.IsCompleted.Should().BeFalse();
-        }
-        finally
-        {
-            first.Dispose();
-        }
+        await Task.Delay(50);
+        startedSecond.Task.IsCompleted.Should().BeFalse();
+
+        first.Dispose();
 
         await secondTask.WaitAsync(TimeSpan.FromSeconds(1));
         sw.Stop();

PerfectNumbers.Core.Tests/HeuristicCombinedPrimeTesterTests.cs

@@ -1,235 +0,0 @@
-using FluentAssertions;
-using Xunit;
-
-namespace PerfectNumbers.Core.Tests;
-
-public class HeuristicCombinedPrimeTesterTests
-{
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData((byte)1)]
-    [InlineData((byte)7)]
-    [InlineData((byte)9)]
-    public void Enumerator_uses_one_a_one_b_schedule_by_default(byte lastDigit)
-    {
-        Span<HeuristicCombinedPrimeTester.HeuristicGroupBSequenceState> groupBState =
-            stackalloc HeuristicCombinedPrimeTester.HeuristicGroupBSequenceState[4];
-
-        var enumerator = HeuristicCombinedPrimeTester.CreateHeuristicDivisorEnumerator(500UL * 500UL, lastDigit, groupBState);
-        var results = new List<HeuristicCombinedPrimeTester.HeuristicDivisorCandidate>(32);
-
-        while (results.Count < 20 && enumerator.TryGetNext(out var candidate))
-        {
-            results.Add(candidate);
-        }
-
-        const int segmentsToCheck = 6;
-        results.Count.Should().BeGreaterThanOrEqualTo(4 + segmentsToCheck * 2);
-        results[0].Value.Should().Be(3UL);
-        results[0].Group.Should().Be(HeuristicCombinedPrimeTester.HeuristicDivisorGroup.GroupAConstant);
-        results[1].Value.Should().Be(7UL);
-        results[1].Group.Should().Be(HeuristicCombinedPrimeTester.HeuristicDivisorGroup.GroupAConstant);
-        results[2].Value.Should().Be(11UL);
-        results[2].Group.Should().Be(HeuristicCombinedPrimeTester.HeuristicDivisorGroup.GroupAConstant);
-        results[3].Value.Should().Be(13UL);
-        results[3].Group.Should().Be(HeuristicCombinedPrimeTester.HeuristicDivisorGroup.GroupAConstant);
-
-        int index = 4;
-
-        for (int segment = 0; segment < segmentsToCheck; segment++)
-        {
-            HeuristicCombinedPrimeTester.HeuristicDivisorCandidate groupACandidate = results[index++];
-            groupACandidate.Value.Should().BeGreaterThan(13UL);
-            (groupACandidate.Value % 10UL).Should().Be(3UL);
-            groupACandidate.Group.Should().NotBe(HeuristicCombinedPrimeTester.HeuristicDivisorGroup.GroupB);
-
-            HeuristicCombinedPrimeTester.HeuristicDivisorCandidate groupBCandidate = results[index++];
-            groupBCandidate.Value.Should().BeGreaterThan(13UL);
-            (groupBCandidate.Value % 10UL).Should().NotBe(3UL);
-            groupBCandidate.Group.Should().Be(HeuristicCombinedPrimeTester.HeuristicDivisorGroup.GroupB);
-        }
-
-    }
-
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData((byte)1)]
-    [InlineData((byte)7)]
-    [InlineData((byte)9)]
-    public void One_a_one_b_pattern_interleaves_group_a_and_group_b_values(byte lastDigit)
-    {
-        ReadOnlySpan<ulong> combined = HeuristicCombinedPrimeTester.GetCombinedDivisors(
-            lastDigit,
-            HeuristicCombinedPrimeTester.CombinedDivisorPattern.OneAOneB);
-
-        combined.Length.Should().BeGreaterThan(18);
-        combined[0].Should().Be(3UL);
-        combined[1].Should().Be(7UL);
-        combined[2].Should().Be(11UL);
-        combined[3].Should().Be(13UL);
-
-        int index = 4;
-        const int segmentsToCheck = 6;
-
-        for (int segment = 0; segment < segmentsToCheck; segment++)
-        {
-            ulong groupAValue = combined[index++];
-            groupAValue.Should().BeGreaterThan(13UL);
-            (groupAValue % 10UL).Should().Be(3UL);
-
-            ulong groupBValue = combined[index++];
-            groupBValue.Should().BeGreaterThan(13UL);
-            (groupBValue % 10UL).Should().NotBe(3UL);
-        }
-    }
-
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData((byte)1)]
-    [InlineData((byte)7)]
-    [InlineData((byte)9)]
-    public void Two_a_one_b_pattern_interleaves_two_group_a_values_before_group_b(byte lastDigit)
-    {
-        ReadOnlySpan<ulong> combined = HeuristicCombinedPrimeTester.GetCombinedDivisors(
-            lastDigit,
-            HeuristicCombinedPrimeTester.CombinedDivisorPattern.TwoAOneB);
-
-        combined.Length.Should().BeGreaterThan(20);
-        combined[0].Should().Be(3UL);
-        combined[1].Should().Be(7UL);
-        combined[2].Should().Be(11UL);
-        combined[3].Should().Be(13UL);
-
-        int index = 4;
-        const int segmentsToCheck = 5;
-
-        for (int segment = 0; segment < segmentsToCheck; segment++)
-        {
-            for (int i = 0; i < 2; i++)
-            {
-                ulong groupAValue = combined[index++];
-                groupAValue.Should().BeGreaterThan(13UL);
-                (groupAValue % 10UL).Should().Be(3UL);
-            }
-
-            ulong groupBValue = combined[index++];
-            groupBValue.Should().BeGreaterThan(13UL);
-            (groupBValue % 10UL).Should().NotBe(3UL);
-        }
-    }
-
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData((byte)1)]
-    [InlineData((byte)7)]
-    [InlineData((byte)9)]
-    public void Three_a_two_b_pattern_interleaves_three_group_a_values_before_two_group_b_values(byte lastDigit)
-    {
-        ReadOnlySpan<ulong> combined = HeuristicCombinedPrimeTester.GetCombinedDivisors(
-            lastDigit,
-            HeuristicCombinedPrimeTester.CombinedDivisorPattern.ThreeATwoB);
-
-        combined.Length.Should().BeGreaterThan(28);
-        combined[0].Should().Be(3UL);
-        combined[1].Should().Be(7UL);
-        combined[2].Should().Be(11UL);
-        combined[3].Should().Be(13UL);
-
-        int index = 4;
-        const int segmentsToCheck = 4;
-
-        for (int segment = 0; segment < segmentsToCheck; segment++)
-        {
-            for (int i = 0; i < 3; i++)
-            {
-                ulong groupAValue = combined[index++];
-                groupAValue.Should().BeGreaterThan(13UL);
-                (groupAValue % 10UL).Should().Be(3UL);
-            }
-
-            for (int i = 0; i < 2; i++)
-            {
-                ulong groupBValue = combined[index++];
-                groupBValue.Should().BeGreaterThan(13UL);
-                (groupBValue % 10UL).Should().NotBe(3UL);
-            }
-        }
-    }
-
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData((byte)1)]
-    [InlineData((byte)7)]
-    [InlineData((byte)9)]
-    public void Three_a_one_b_pattern_interleaves_three_group_a_values_before_group_b(byte lastDigit)
-    {
-        ReadOnlySpan<ulong> combined = HeuristicCombinedPrimeTester.GetCombinedDivisors(
-            lastDigit,
-            HeuristicCombinedPrimeTester.CombinedDivisorPattern.ThreeAOneB);
-
-        combined.Length.Should().BeGreaterThan(24);
-        combined[0].Should().Be(3UL);
-        combined[1].Should().Be(7UL);
-        combined[2].Should().Be(11UL);
-        combined[3].Should().Be(13UL);
-
-        int index = 4;
-        const int segmentsToCheck = 4;
-
-        for (int segment = 0; segment < segmentsToCheck; segment++)
-        {
-            for (int i = 0; i < 3; i++)
-            {
-                ulong groupAValue = combined[index++];
-                groupAValue.Should().BeGreaterThan(13UL);
-                (groupAValue % 10UL).Should().Be(3UL);
-            }
-
-            ulong groupBValue = combined[index++];
-            groupBValue.Should().BeGreaterThan(13UL);
-            (groupBValue % 10UL).Should().NotBe(3UL);
-        }
-    }
-
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData(0UL)]
-    [InlineData(1UL)]
-    [InlineData(2UL)]
-    [InlineData(3UL)]
-    [InlineData(4UL)]
-    [InlineData(5UL)]
-    [InlineData(8UL)]
-    [InlineData(9UL)]
-    [InlineData(15UL)]
-    [InlineData(16UL)]
-    [InlineData(17UL)]
-    [InlineData(24UL)]
-    [InlineData(25UL)]
-    [InlineData(26UL)]
-    [InlineData(255UL)]
-    [InlineData(256UL)]
-    [InlineData(257UL)]
-    [InlineData(1_000UL)]
-    [InlineData(1_048_575UL)]
-    [InlineData(1_048_576UL)]
-    [InlineData(1_048_577UL)]
-    [InlineData(4_000_000UL)]
-    [InlineData(4_000_001UL)]
-    [InlineData(4_000_004UL)]
-    [InlineData(65_535_999UL)]
-    [InlineData(65_536_000UL)]
-    [InlineData(65_536_001UL)]
-    [InlineData(4_294_967_295UL)]
-    [InlineData(4_294_967_296UL)]
-    [InlineData(4_294_967_297UL)]
-    [InlineData(18_446_744_073_709_551_615UL)]
-    [InlineData(18_446_744_073_709_551_614UL)]
-    [InlineData(18_446_744_073_709_551_613UL)]
-    public void ComputeHeuristicDivisorSquareLimit_returns_input_value(ulong value)
-    {
-        ulong limit = HeuristicCombinedPrimeTester.ComputeHeuristicDivisorSquareLimit(value);
-
-        limit.Should().Be(value);
-    }
-}

PerfectNumbers.Core.Tests/MersenneNumberDivisorByDivisorTesterTests.cs

@@ -11,7 +11,7 @@ public class MersenneNumberDivisorByDivisorTesterTests
     {
         var candidates = new List<ulong> { 5UL, 7UL, 11UL, 13UL };
         var tester = new FakeTester();
-        var results = new List<(ulong Prime, bool Searched, bool Detailed, bool Passed, ulong Divisor)>();
+        var results = new List<(ulong Prime, bool Searched, bool Detailed, bool Passed)>();
         int compositeMarks = 0;
         int clearedMarks = 0;
 
@@ -22,7 +22,7 @@ public class MersenneNumberDivisorByDivisorTesterTests
             startPrime: 0UL,
             markComposite: () => compositeMarks++,
             clearComposite: () => clearedMarks++,
-            printResult: (prime, searched, detailed, passed, divisor) => results.Add((prime, searched, detailed, passed, divisor)),
+            printResult: (prime, searched, detailed, passed) => results.Add((prime, searched, detailed, passed)),
             threadCount: 1,
             primesPerTask: 2);
 
@@ -32,10 +32,10 @@ public class MersenneNumberDivisorByDivisorTesterTests
         results.Should().Equal(
             new[]
             {
-                (5UL, true, true, true, 0UL),
-                (7UL, true, true, false, 7UL),
-                (11UL, true, true, false, 11UL),
-                (13UL, true, true, true, 0UL),
+                (5UL, true, true, true),
+                (7UL, true, true, false),
+                (11UL, true, true, false),
+                (13UL, true, true, true),
             });
     }
 
@@ -57,23 +57,10 @@ public class MersenneNumberDivisorByDivisorTesterTests
             return DivisorLimit;
         }
 
-        public bool IsPrime(ulong prime, out bool divisorsExhausted, out ulong divisor)
+        public bool IsPrime(ulong prime, out bool divisorsExhausted)
         {
             divisorsExhausted = true;
-            if (prime % 7UL == 0UL)
-            {
-                divisor = 7UL;
-                return false;
-            }
-
-            if (prime % 11UL == 0UL)
-            {
-                divisor = 11UL;
-                return false;
-            }
-
-            divisor = 0UL;
-            return true;
+            return prime % 7UL != 0UL && prime % 11UL != 0UL;
         }
 
         public IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession()
@@ -96,7 +83,7 @@ public class MersenneNumberDivisorByDivisorTesterTests
                 throw new NotSupportedException();
             }
 
-            public void Return()
+            public void Dispose()
             {
             }
         }

PerfectNumbers.Core.Tests/MersenneNumberDivisorCpuTesterTests.cs

@@ -13,17 +13,14 @@ public class MersenneNumberDivisorCpuTesterTests
                 var tester = new MersenneNumberDivisorByDivisorCpuTester();
                 tester.ConfigureFromMaxPrime(11UL);
 
-                tester.IsPrime(5UL, out bool divisorsExhausted, out ulong divisor).Should().BeTrue();
+                tester.IsPrime(5UL, out bool divisorsExhausted).Should().BeTrue();
                 divisorsExhausted.Should().BeTrue();
-                divisor.Should().Be(0UL);
 
-                tester.IsPrime(7UL, out divisorsExhausted, out divisor).Should().BeTrue();
+                tester.IsPrime(7UL, out divisorsExhausted).Should().BeTrue();
                 divisorsExhausted.Should().BeTrue();
-                divisor.Should().Be(0UL);
 
-                tester.IsPrime(11UL, out divisorsExhausted, out divisor).Should().BeFalse();
+                tester.IsPrime(11UL, out divisorsExhausted).Should().BeFalse();
                 divisorsExhausted.Should().BeTrue();
-                divisor.Should().BeGreaterThan(0UL);
         }
 
         [Fact]
@@ -33,25 +30,18 @@ public class MersenneNumberDivisorCpuTesterTests
                 var tester = new MersenneNumberDivisorByDivisorCpuTester();
                 tester.ConfigureFromMaxPrime(13UL);
 
-                var session = tester.CreateDivisorSession();
-                try
-                {
-                        ulong[] primes = { 5UL, 7UL, 11UL, 13UL };
-                        byte[] hits = new byte[primes.Length];
+                using var session = tester.CreateDivisorSession();
+                ulong[] primes = { 5UL, 7UL, 11UL, 13UL };
+                byte[] hits = new byte[primes.Length];
 
-                        ulong cycle23 = MersenneDivisorCycles.CalculateCycleLength(23UL, MontgomeryDivisorData.FromModulus(23UL));
-                        session.CheckDivisor(23UL, MontgomeryDivisorData.FromModulus(23UL), cycle23, primes, hits);
-                        hits.Should().ContainInOrder(new byte[] { 0, 0, 1, 0 });
+                ulong cycle23 = MersenneDivisorCycles.CalculateCycleLength(23UL, MontgomeryDivisorData.FromModulus(23UL));
+                session.CheckDivisor(23UL, MontgomeryDivisorData.FromModulus(23UL), cycle23, primes, hits);
+                hits.Should().ContainInOrder(new byte[] { 0, 0, 1, 0 });
 
-                        Array.Fill(hits, (byte)0);
-                        ulong cycle31 = MersenneDivisorCycles.CalculateCycleLength(31UL, MontgomeryDivisorData.FromModulus(31UL));
-                        session.CheckDivisor(31UL, MontgomeryDivisorData.FromModulus(31UL), cycle31, primes, hits);
-                        hits.Should().ContainInOrder(new byte[] { 1, 0, 0, 0 });
-                }
-                finally
-                {
-                        session.Return();
-                }
+                Array.Fill(hits, (byte)0);
+                ulong cycle31 = MersenneDivisorCycles.CalculateCycleLength(31UL, MontgomeryDivisorData.FromModulus(31UL));
+                session.CheckDivisor(31UL, MontgomeryDivisorData.FromModulus(31UL), cycle31, primes, hits);
+                hits.Should().ContainInOrder(new byte[] { 1, 0, 0, 0 });
         }
 
         [Fact]
@@ -61,22 +51,15 @@ public class MersenneNumberDivisorCpuTesterTests
                 var tester = new MersenneNumberDivisorByDivisorCpuTester();
                 tester.ConfigureFromMaxPrime(43UL);
 
-                var session = tester.CreateDivisorSession();
-                try
-                {
-                        ulong[] exponents = { 6UL, 7UL, 9UL, 10UL, 12UL };
-                        byte[] hits = new byte[exponents.Length];
+                using var session = tester.CreateDivisorSession();
+                ulong[] exponents = { 6UL, 7UL, 9UL, 10UL, 12UL };
+                byte[] hits = new byte[exponents.Length];
 
-                        MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(7UL);
-                        ulong cycle = MersenneDivisorCycles.CalculateCycleLength(7UL, divisorData);
-                        session.CheckDivisor(7UL, divisorData, cycle, exponents, hits);
+                MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(7UL);
+                ulong cycle = MersenneDivisorCycles.CalculateCycleLength(7UL, divisorData);
+                session.CheckDivisor(7UL, divisorData, cycle, exponents, hits);
 
-                        hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
-                }
-                finally
-                {
-                        session.Return();
-                }
+                hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
         }
 
         [Fact]
@@ -86,22 +69,15 @@ public class MersenneNumberDivisorCpuTesterTests
                 var tester = new MersenneNumberDivisorByDivisorCpuTester();
                 tester.ConfigureFromMaxPrime(61UL);
 
-                var session = tester.CreateDivisorSession();
-                try
-                {
-                        ulong[] exponents = { 10UL, 11UL, 20UL, 21UL, 30UL };
-                        byte[] hits = new byte[exponents.Length];
+                using var session = tester.CreateDivisorSession();
+                ulong[] exponents = { 10UL, 11UL, 20UL, 21UL, 30UL };
+                byte[] hits = new byte[exponents.Length];
 
-                        MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(11UL);
-                        ulong cycle = MersenneDivisorCycles.CalculateCycleLength(11UL, divisorData);
-                        session.CheckDivisor(11UL, divisorData, cycle, exponents, hits);
+                MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(11UL);
+                ulong cycle = MersenneDivisorCycles.CalculateCycleLength(11UL, divisorData);
+                session.CheckDivisor(11UL, divisorData, cycle, exponents, hits);
 
-                        hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
-                }
-                finally
-                {
-                        session.Return();
-                }
+                hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
         }
 }
 

PerfectNumbers.Core.Tests/MersenneNumberDivisorGpuTesterTests.cs

@@ -73,17 +73,14 @@ public class MersenneNumberDivisorGpuTesterTests
         var tester = new MersenneNumberDivisorByDivisorGpuTester();
         tester.ConfigureFromMaxPrime(43UL);
 
-        tester.IsPrime(31UL, out bool exhausted, out ulong divisor).Should().BeTrue();
+        tester.IsPrime(31UL, out bool exhausted).Should().BeTrue();
         exhausted.Should().BeTrue();
-        divisor.Should().Be(0UL);
 
-        tester.IsPrime(37UL, out exhausted, out divisor).Should().BeFalse();
+        tester.IsPrime(37UL, out exhausted).Should().BeFalse();
         exhausted.Should().BeTrue();
-        divisor.Should().BeGreaterThan(0UL);
 
-        tester.IsPrime(43UL, out exhausted, out divisor).Should().BeFalse();
+        tester.IsPrime(43UL, out exhausted).Should().BeFalse();
         exhausted.Should().BeTrue();
-        divisor.Should().BeGreaterThan(0UL);
     }
 
     [Fact]
@@ -108,15 +105,12 @@ public class MersenneNumberDivisorGpuTesterTests
         var tester = new MersenneNumberDivisorByDivisorGpuTester();
         tester.ConfigureFromMaxPrime(41UL);
 
-        tester.IsPrime(31UL, out _, out ulong divisor).Should().BeTrue();
-        divisor.Should().Be(0UL);
-        tester.IsPrime(37UL, out bool exhausted, out divisor).Should().BeFalse();
+        tester.IsPrime(31UL, out _).Should().BeTrue();
+        tester.IsPrime(37UL, out bool exhausted).Should().BeFalse();
         exhausted.Should().BeTrue();
-        divisor.Should().BeGreaterThan(0UL);
 
-        tester.IsPrime(41UL, out bool divisorsExhausted, out divisor).Should().BeFalse();
+        tester.IsPrime(41UL, out bool divisorsExhausted).Should().BeFalse();
         divisorsExhausted.Should().BeTrue();
-        divisor.Should().BeGreaterThan(0UL);
     }
 
 
@@ -130,16 +124,8 @@ public class MersenneNumberDivisorGpuTesterTests
         var tester = new MersenneNumberDivisorByDivisorGpuTester();
         tester.ConfigureFromMaxPrime(exponent);
 
-        tester.IsPrime(exponent, out bool exhausted, out ulong divisor).Should().Be(expectedPrime);
+        tester.IsPrime(exponent, out bool exhausted).Should().Be(expectedPrime);
         exhausted.Should().BeTrue();
-        if (expectedPrime)
-        {
-            divisor.Should().Be(0UL);
-        }
-        else
-        {
-            divisor.Should().BeGreaterThan(0UL);
-        }
     }
     [Fact]
     [Trait("Category", "Fast")]
@@ -152,9 +138,8 @@ public class MersenneNumberDivisorGpuTesterTests
 
         tester.ConfigureFromMaxPrime(43UL);
 
-        tester.IsPrime(41UL, out bool divisorsExhausted, out ulong divisor).Should().BeFalse();
+        tester.IsPrime(41UL, out bool divisorsExhausted).Should().BeFalse();
         divisorsExhausted.Should().BeTrue();
-        divisor.Should().BeGreaterThan(0UL);
     }
 
     [Fact]
@@ -164,20 +149,13 @@ public class MersenneNumberDivisorGpuTesterTests
         var tester = new MersenneNumberDivisorByDivisorGpuTester();
         tester.ConfigureFromMaxPrime(43UL);
 
-        var session = tester.CreateDivisorSession();
-        try
-        {
-            ulong[] primes = { 31UL, 37UL, 41UL };
-            byte[] hits = new byte[primes.Length];
+        using var session = tester.CreateDivisorSession();
+        ulong[] primes = { 31UL, 37UL, 41UL };
+        byte[] hits = new byte[primes.Length];
 
-            session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), 0UL, primes, hits);
+        session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), 0UL, primes, hits);
 
-            hits.Should().ContainInOrder(new byte[] { 0, 1, 0 });
-        }
-        finally
-        {
-            session.Return();
-        }
+        hits.Should().ContainInOrder(new byte[] { 0, 1, 0 });
     }
 
     [Fact]
@@ -187,25 +165,18 @@ public class MersenneNumberDivisorGpuTesterTests
         var tester = new MersenneNumberDivisorByDivisorGpuTester();
         tester.ConfigureFromMaxPrime(43UL);
 
-        var session = tester.CreateDivisorSession();
-        try
-        {
-            ulong[] primes = { 31UL, 37UL, 41UL, 43UL };
-            byte[] hits = new byte[primes.Length];
+        using var session = tester.CreateDivisorSession();
+        ulong[] primes = { 31UL, 37UL, 41UL, 43UL };
+        byte[] hits = new byte[primes.Length];
 
-            ulong cycle223 = MersenneDivisorCycles.CalculateCycleLength(223UL, MontgomeryDivisorData.FromModulus(223UL));
-            session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), cycle223, primes, hits);
-            hits.Should().ContainInOrder(new byte[] { 0, 1, 0, 0 });
+        ulong cycle223 = MersenneDivisorCycles.CalculateCycleLength(223UL, MontgomeryDivisorData.FromModulus(223UL));
+        session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), cycle223, primes, hits);
+        hits.Should().ContainInOrder(new byte[] { 0, 1, 0, 0 });
 
-            Array.Fill(hits, (byte)0);
-            ulong cycle13367 = MersenneDivisorCycles.CalculateCycleLength(13367UL, MontgomeryDivisorData.FromModulus(13367UL));
-            session.CheckDivisor(13367UL, MontgomeryDivisorData.FromModulus(13367UL), cycle13367, primes, hits);
-            hits.Should().ContainInOrder(new byte[] { 0, 0, 1, 0 });
-        }
-        finally
-        {
-            session.Return();
-        }
+        Array.Fill(hits, (byte)0);
+        ulong cycle13367 = MersenneDivisorCycles.CalculateCycleLength(13367UL, MontgomeryDivisorData.FromModulus(13367UL));
+        session.CheckDivisor(13367UL, MontgomeryDivisorData.FromModulus(13367UL), cycle13367, primes, hits);
+        hits.Should().ContainInOrder(new byte[] { 0, 0, 1, 0 });
     }
 
     [Fact]
@@ -219,21 +190,14 @@ public class MersenneNumberDivisorGpuTesterTests
 
         tester.ConfigureFromMaxPrime(47UL);
 
-        var session = tester.CreateDivisorSession();
-        try
-        {
-            ulong[] primes = { 31UL, 37UL, 41UL, 43UL, 47UL };
-            byte[] hits = new byte[primes.Length];
+        using var session = tester.CreateDivisorSession();
+        ulong[] primes = { 31UL, 37UL, 41UL, 43UL, 47UL };
+        byte[] hits = new byte[primes.Length];
 
-            ulong cycle223 = MersenneDivisorCycles.CalculateCycleLength(223UL, MontgomeryDivisorData.FromModulus(223UL));
-            session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), cycle223, primes, hits);
+        ulong cycle223 = MersenneDivisorCycles.CalculateCycleLength(223UL, MontgomeryDivisorData.FromModulus(223UL));
+        session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), cycle223, primes, hits);
 
-            hits.Should().ContainInOrder(new byte[] { 0, 1, 0, 0, 0 });
-        }
-        finally
-        {
-            session.Return();
-        }
+        hits.Should().ContainInOrder(new byte[] { 0, 1, 0, 0, 0 });
     }
 
     [Fact]
@@ -246,23 +210,16 @@ public class MersenneNumberDivisorGpuTesterTests
         };
         tester.ConfigureFromMaxPrime(43UL);
 
-        var session = tester.CreateDivisorSession();
-        try
-        {
-            ulong[] exponents = { 6UL, 7UL, 9UL, 10UL, 12UL };
-            byte[] hits = new byte[exponents.Length];
+        using var session = tester.CreateDivisorSession();
+        ulong[] exponents = { 6UL, 7UL, 9UL, 10UL, 12UL };
+        byte[] hits = new byte[exponents.Length];
 
-            MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(7UL);
-            ulong cycle = MersenneDivisorCycles.CalculateCycleLength(7UL, divisorData);
+        MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(7UL);
+        ulong cycle = MersenneDivisorCycles.CalculateCycleLength(7UL, divisorData);
 
-            session.CheckDivisor(7UL, divisorData, cycle, exponents, hits);
+        session.CheckDivisor(7UL, divisorData, cycle, exponents, hits);
 
-            hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
-        }
-        finally
-        {
-            session.Return();
-        }
+        hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
     }
 
     [Fact]
@@ -275,23 +232,16 @@ public class MersenneNumberDivisorGpuTesterTests
         };
         tester.ConfigureFromMaxPrime(61UL);
 
-        var session = tester.CreateDivisorSession();
-        try
-        {
-            ulong[] exponents = { 10UL, 11UL, 20UL, 21UL, 30UL };
-            byte[] hits = new byte[exponents.Length];
+        using var session = tester.CreateDivisorSession();
+        ulong[] exponents = { 10UL, 11UL, 20UL, 21UL, 30UL };
+        byte[] hits = new byte[exponents.Length];
 
-            MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(11UL);
-            ulong cycle = MersenneDivisorCycles.CalculateCycleLength(11UL, divisorData);
+        MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(11UL);
+        ulong cycle = MersenneDivisorCycles.CalculateCycleLength(11UL, divisorData);
 
-            session.CheckDivisor(11UL, divisorData, cycle, exponents, hits);
+        session.CheckDivisor(11UL, divisorData, cycle, exponents, hits);
 
-            hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
-        }
-        finally
-        {
-            session.Return();
-        }
+        hits.Should().Equal(new byte[] { 1, 0, 1, 0, 1 });
     }
 
     [Fact]
@@ -324,15 +274,15 @@ public class MersenneNumberDivisorGpuTesterTests
                 .GetField("_divisorLimit", BindingFlags.NonPublic | BindingFlags.Instance)!
                 .SetValue(tester, 200UL);
 
-            tester.IsPrime(19UL, out bool divisorsExhausted, out ulong divisor).Should().BeTrue();
+            tester.IsPrime(19UL, out bool divisorsExhausted).Should().BeTrue();
             divisorsExhausted.Should().BeTrue();
-            divisor.Should().Be(0UL);
         }
         finally
         {
             tableField.SetValue(cycles, originalTable);
             smallCyclesField.SetValue(cycles, originalSmall);
             DivisorCycleCache.Shared.RefreshSnapshot();
+            GpuContextPool.DisposeAll();
         }
     }
 
@@ -347,21 +297,14 @@ public class MersenneNumberDivisorGpuTesterTests
 
         tester.ConfigureFromMaxPrime(47UL);
 
-        var session = tester.CreateDivisorSession();
-        try
-        {
-            ulong[] primes = { 31UL, 37UL, 41UL, 43UL, 47UL };
-            byte[] hits = new byte[primes.Length];
+        using var session = tester.CreateDivisorSession();
+        ulong[] primes = { 31UL, 37UL, 41UL, 43UL, 47UL };
+        byte[] hits = new byte[primes.Length];
 
-            ulong cycle223 = MersenneDivisorCycles.CalculateCycleLength(223UL, MontgomeryDivisorData.FromModulus(223UL));
-            session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), cycle223, primes, hits);
+        ulong cycle223 = MersenneDivisorCycles.CalculateCycleLength(223UL, MontgomeryDivisorData.FromModulus(223UL));
+        session.CheckDivisor(223UL, MontgomeryDivisorData.FromModulus(223UL), cycle223, primes, hits);
 
-            hits.Should().ContainInOrder(new byte[] { 0, 1, 0, 0, 0 });
-        }
-        finally
-        {
-            session.Return();
-        }
+        hits.Should().ContainInOrder(new byte[] { 0, 1, 0, 0, 0 });
     }
 }
 

PerfectNumbers.Core.Tests/MersenneNumberIncrementalCpuTesterTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Cpu;
 using Xunit;
 using UInt128 = System.UInt128;

PerfectNumbers.Core.Tests/MersenneNumberIncrementalGpuTesterTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
 using Xunit;
 using UInt128 = System.UInt128;

PerfectNumbers.Core.Tests/MersenneNumberOrderCpuTesterTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Cpu;
 using Xunit;
 using UInt128 = System.UInt128;

PerfectNumbers.Core.Tests/MersenneNumberOrderGpuTesterTests.cs

@@ -1,5 +1,6 @@
 using System.Reflection;
 using FluentAssertions;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
 using Xunit;
 using UInt128 = System.UInt128;
@@ -54,6 +55,7 @@ public class MersenneNumberOrderGpuTesterTests
             ulong[]? backupSmall = originalSmall is null ? null : (ulong[])originalSmall.Clone();
 
             cycles.LoadFrom(tempPath);
+            GpuContextPool.DisposeAll();
 
             try
             {
@@ -73,6 +75,7 @@ public class MersenneNumberOrderGpuTesterTests
             {
                 tableField.SetValue(cycles, originalTable);
                 smallCyclesField.SetValue(cycles, backupSmall);
+                GpuContextPool.DisposeAll();
             }
         }
         finally

PerfectNumbers.Core.Tests/MersenneNumberResidueCpuTesterTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Cpu;
 using Xunit;
 using UInt128 = System.UInt128;

PerfectNumbers.Core.Tests/MersenneNumberResidueGpuTesterTests.cs

@@ -1,4 +1,5 @@
 using FluentAssertions;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
 using Xunit;
 using UInt128 = System.UInt128;

PerfectNumbers.Core.Tests/PrimeTester/PrimeTesterIsPrimeTests.cs

@@ -17,29 +17,12 @@ public class PrimeTesterIsPrimeTests
     [InlineData(97UL, true)]
     [InlineData(133UL, false)]
     [InlineData(137UL, true)]
-    [InlineData(143UL, false)]
-    [InlineData(199UL, true)]
-    [InlineData(209UL, false)]
-    [InlineData(403UL, false)]
     [InlineData(341UL, false)]
     public void IsPrime_returns_expected_results(ulong n, bool expected)
     {
         var tester = new PrimeTester();
 
-		PrimeTester.IsPrime(n).Should().Be(expected);
-    }
-
-    [Theory]
-    [Trait("Category", "Fast")]
-    [InlineData(139UL, true)]
-    [InlineData(189UL, false)]
-    [InlineData(193UL, true)]
-    [InlineData(279UL, false)]
-    public void IsPrimeGpu_uses_residue_specific_tables(ulong n, bool expected)
-    {
-        var tester = new PrimeTester();
-
-		PrimeTester.IsPrimeGpu(n).Should().Be(expected);
+        tester.IsPrime(n, CancellationToken.None).Should().Be(expected);
     }
 
     [Fact]
@@ -47,14 +30,20 @@ public class PrimeTesterIsPrimeTests
     public void IsPrimeGpu_falls_back_to_cpu_when_forced()
     {
         var tester = new PrimeTester();
-        PrimeTester.IsPrime(137UL).Should().BeTrue();
-        PrimeTester.IsPrime(341UL).Should().BeFalse();
+        GpuContextPool.ForceCpu = true;
+
+        tester.IsPrimeGpu(137UL, CancellationToken.None).Should().BeTrue();
+
+        tester.IsPrimeGpu(341UL, CancellationToken.None).Should().BeFalse();
+
+        GpuContextPool.ForceCpu = false;
     }
 
     [Fact]
     [Trait("Category", "Fast")]
     public void IsPrimeGpu_handles_parallel_calls_for_known_primes()
     {
+        GpuContextPool.ForceCpu = false;
         GpuPrimeWorkLimiter.SetLimit(64);
         PrimeTester.GpuBatchSize = 256_000;
 
@@ -64,7 +53,7 @@ public class PrimeTesterIsPrimeTests
         var testers = new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true);
         Parallel.For(0, primes.Length, i =>
         {
-            results[i] = PrimeTester.IsPrimeGpu(primes[i]);
+            results[i] = testers.Value!.IsPrimeGpu(primes[i], CancellationToken.None);
         });
 
         results.Should().AllBeEquivalentTo(true);
@@ -73,7 +62,7 @@ public class PrimeTesterIsPrimeTests
         {
             foreach (ulong prime in primes)
             {
-				PrimeTester.IsPrimeGpu(prime).Should().BeTrue();
+                testers.Value!.IsPrimeGpu(prime, CancellationToken.None).Should().BeTrue();
             }
         });
     }

PerfectNumbers.Core.Tests/PrimesGeneratorTests.cs

@@ -32,39 +32,14 @@ public class PrimesGeneratorTests
         var lastOnePow2 = PrimesGenerator.SmallPrimesPow2LastOne;
         var lastSeven = PrimesGenerator.SmallPrimesLastSeven;
         var lastSevenPow2 = PrimesGenerator.SmallPrimesPow2LastSeven;
-        var lastThree = DivisorGenerator.SmallPrimesLastThree;
-        var lastThreePow2 = DivisorGenerator.SmallPrimesPow2LastThree;
-        var lastNine = DivisorGenerator.SmallPrimesLastNine;
-        var lastNinePow2 = DivisorGenerator.SmallPrimesPow2LastNine;
-        var lastOneWithoutThree = DivisorGenerator.SmallPrimesLastOneWithoutLastThree;
-        var lastOneWithoutThreePow2 = DivisorGenerator.SmallPrimesPow2LastOneWithoutLastThree;
-        var lastSevenWithoutThree = DivisorGenerator.SmallPrimesLastSevenWithoutLastThree;
-        var lastSevenWithoutThreePow2 = DivisorGenerator.SmallPrimesPow2LastSevenWithoutLastThree;
-        var lastNineWithoutThree = DivisorGenerator.SmallPrimesLastNineWithoutLastThree;
-        var lastNineWithoutThreePow2 = DivisorGenerator.SmallPrimesPow2LastNineWithoutLastThree;
 
         lastOne.Length.Should().Be((int)PerfectNumberConstants.PrimesLimit);
         lastSeven.Length.Should().Be((int)PerfectNumberConstants.PrimesLimit);
-        lastThree.Length.Should().Be((int)PerfectNumberConstants.PrimesLimit);
-        lastNine.Length.Should().Be((int)PerfectNumberConstants.PrimesLimit);
-        lastOneWithoutThree.Length.Should().BeGreaterThan(0);
-        lastSevenWithoutThree.Length.Should().BeGreaterThan(0);
-        lastNineWithoutThree.Length.Should().BeGreaterThan(0);
-        lastOneWithoutThree.Length.Should().BeLessThan(lastOne.Length);
-        lastSevenWithoutThree.Length.Should().BeLessThan(lastSeven.Length);
-        lastNineWithoutThree.Length.Should().BeLessThan(lastNine.Length);
         lastOnePow2.Length.Should().Be(lastOne.Length);
         lastSevenPow2.Length.Should().Be(lastSeven.Length);
-        lastThreePow2.Length.Should().Be(lastThree.Length);
-        lastNinePow2.Length.Should().Be(lastNine.Length);
-        lastOneWithoutThreePow2.Length.Should().Be(lastOneWithoutThree.Length);
-        lastSevenWithoutThreePow2.Length.Should().Be(lastSevenWithoutThree.Length);
-        lastNineWithoutThreePow2.Length.Should().Be(lastNineWithoutThree.Length);
 
         lastOne[..5].Should().Equal([3U, 7U, 11U, 13U, 19U]);
         lastSeven[..5].Should().Equal([3U, 7U, 11U, 13U, 17U]);
-        lastThree[..6].Should().Equal([3U, 7U, 11U, 13U, 17U, 19U]);
-        lastNine[..6].Should().Equal([3U, 7U, 11U, 13U, 17U, 19U]);
 
         for (int i = 0; i < lastOne.Length; i++)
         {
@@ -83,64 +58,6 @@ public class PrimesGeneratorTests
                 .Should().BeTrue();
             lastSevenPow2[i].Should().Be(prime * (ulong)prime);
         }
-
-        for (int i = 0; i < lastThree.Length; i++)
-        {
-            uint prime = lastThree[i];
-            uint mod10 = prime % 10U;
-            (mod10 == 3U || mod10 == 7U || prime == 11U || prime == 19U)
-                .Should().BeTrue();
-            lastThreePow2[i].Should().Be(prime * (ulong)prime);
-        }
-
-
-        lastOneWithoutThree.Should().NotBeEmpty();
-        lastSevenWithoutThree.Should().NotBeEmpty();
-        lastNineWithoutThree.Should().NotBeEmpty();
-
-        for (int i = 0; i < lastOneWithoutThree.Length; i++)
-        {
-            uint prime = lastOneWithoutThree[i];
-            (prime % 10U != 3U).Should().BeTrue();
-            if (i > 0)
-            {
-                prime.Should().BeGreaterThan(lastOneWithoutThree[i - 1]);
-            }
-
-            lastOneWithoutThreePow2[i].Should().Be(prime * (ulong)prime);
-        }
-
-        for (int i = 0; i < lastSevenWithoutThree.Length; i++)
-        {
-            uint prime = lastSevenWithoutThree[i];
-            (prime % 10U != 3U).Should().BeTrue();
-            if (i > 0)
-            {
-                prime.Should().BeGreaterThan(lastSevenWithoutThree[i - 1]);
-            }
-
-            lastSevenWithoutThreePow2[i].Should().Be(prime * (ulong)prime);
-        }
-
-        for (int i = 0; i < lastNineWithoutThree.Length; i++)
-        {
-            uint prime = lastNineWithoutThree[i];
-            (prime % 10U != 3U).Should().BeTrue();
-            if (i > 0)
-            {
-                prime.Should().BeGreaterThan(lastNineWithoutThree[i - 1]);
-            }
-
-            lastNineWithoutThreePow2[i].Should().Be(prime * (ulong)prime);
-        }
-
-        for (int i = 0; i < lastNine.Length; i++)
-        {
-            uint prime = lastNine[i];
-            uint mod10 = prime % 10U;
-            (mod10 == 3U || mod10 == 7U || mod10 == 9U || prime == 11U)
-                .Should().BeTrue();
-            lastNinePow2[i].Should().Be(prime * (ulong)prime);
-        }
     }
 }
+

PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs

@@ -2,8 +2,11 @@ namespace PerfectNumbers.Core.Cpu;
 
 internal sealed class MersenneCpuDivisorScanSession : IMersenneNumberDivisorByDivisorTester.IDivisorScanSession
 {
+    private bool _disposed;
+
     public void Reset()
     {
+        _disposed = false;
     }
 
     public void CheckDivisor(
@@ -62,8 +65,14 @@ internal sealed class MersenneCpuDivisorScanSession : IMersenneNumberDivisorByDi
         }
     }
 
-    public void Return()
+    public void Dispose()
     {
+        if (_disposed)
+        {
+            throw new ObjectDisposedException(nameof(MersenneCpuDivisorScanSession), "Divisor scan session disposed twice.");
+        }
+
+        _disposed = true;
         ThreadStaticPools.ReturnMersenneCpuDivisorSession(this);
     }
 }

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs

@@ -1,510 +1,284 @@
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using PerfectNumbers.Core;
 using PerfectNumbers.Core.Gpu;
-using PerfectNumbers.Core.Gpu.Accelerators;
 
 namespace PerfectNumbers.Core.Cpu;
 
 public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDivisorByDivisorTester
 {
-	private ulong _divisorLimit;
-	private int _batchSize = 1_024;
-
-	[ThreadStatic]
-	private static GpuUInt128WorkSet _divisorScanGpuWorkSet;
-
-	private struct GpuUInt128WorkSet
-	{
-		public GpuUInt128 Step;
-		public GpuUInt128 Divisor;
-		public GpuUInt128 Limit;
-	}
-
-	public int BatchSize
-	{
-		get => _batchSize;
-		set => _batchSize = Math.Max(1, value);
-	}
-
-	public void ConfigureFromMaxPrime(ulong maxPrime)
-	{
-		_divisorLimit = ComputeDivisorLimitFromMaxPrime(maxPrime);
-	}
-
-	public ulong DivisorLimit
-	{
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		get
-		{
-			return _divisorLimit;
-		}
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ulong GetAllowedMaxDivisor(ulong prime) => ComputeAllowedMaxDivisor(prime, _divisorLimit);
-
-	public bool IsPrime(ulong prime, out bool divisorsExhausted, out ulong divisor)
-	{
-		ulong allowedMax = ComputeAllowedMaxDivisor(prime, _divisorLimit);
-
-		// The CPU by-divisor run always hands us primes with enormous divisor limits, so the fallback below never executes.
-		// if (allowedMax < 3UL)
-		// {
-		//     // EvenPerfectBitScanner routes primes below the small-divisor cutoff to the GPU path, so the CPU path still sees
-		//     // trivial candidates during targeted tests. Short-circuit here to keep those runs aligned with the production flow.
-		//     divisorsExhausted = true;
-		//     return true;
-		// }
-
-		bool processedAll;
-
-		bool composite = CheckDivisors(
-			prime,
-			allowedMax,
-			out processedAll,
-			out divisor);
-
-		if (composite)
-		{
-			divisorsExhausted = true;
-			return false;
-		}
-
-		divisorsExhausted = processedAll || composite;
-		divisor = 0UL;
-		return true;
-	}
-
-	public void PrepareCandidates(in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
-	{
-		ulong divisorLimit = _divisorLimit;
-		int length = primes.Length;
-		for (int index = 0; index < length; index++)
-		{
-			allowedMaxValues[index] = ComputeAllowedMaxDivisor(primes[index], divisorLimit);
-		}
-	}
-
-	public IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession()
-	{
-		MersenneCpuDivisorScanSession? session = ThreadStaticPools.RentMersenneCpuDivisorSession();
-		if (session is not null)
-		{
-			return session;
-		}
-
-		return new MersenneCpuDivisorScanSession();
-	}
-
-	private bool CheckDivisors(
-		ulong prime,
-		ulong allowedMax,
-		out bool processedAll,
-		out ulong foundDivisor)
-	{
-		foundDivisor = 0UL;
-		// The EvenPerfectBitScanner feeds primes >= 138,000,000 here, so allowedMax >= 3 in production runs.
-		// Keeping the guard commented out documents the reasoning for benchmarks and tests.
-		// if (allowedMax < 3UL)
-		// {
-		//     return false;
-		// }
-
-		ref GpuUInt128WorkSet workSet = ref _divisorScanGpuWorkSet;
-
-		ref GpuUInt128 step = ref workSet.Step;
-		step.High = 0UL;
-		step.Low = prime;
-		step.ShiftLeft(1);
-
-		ref GpuUInt128 limit = ref workSet.Limit;
-		limit.High = 0UL;
-		limit.Low = allowedMax;
-
-		ref GpuUInt128 divisor = ref workSet.Divisor;
-		divisor.High = step.High;
-		divisor.Low = step.Low;
-		divisor.Add(1UL);
-		if (divisor.CompareTo(limit) > 0)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		// Intentionally recomputes factorizations without a per-thread cache.
-		// The previous factor cache recorded virtually no hits and only slowed down the scan.
-		_ = DivisorCycleCache.Shared;
-
-		ulong stepHigh = step.High;
-		ulong stepLow = step.Low;
-		ulong limitHigh = limit.High;
-		ulong divisorLow = divisor.Low;
-
-		// Keep the divisibility filters aligned with the divisor-cycle generator so the
-		// CPU path never requests cycles that were skipped during cache creation.
-		LastDigit lastDigit = (prime & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
-		ushort decimalMask = DivisorGenerator.GetDecimalMask(lastDigit);
-
-		byte step10;
-		byte step8;
-		byte step3;
-		byte step7;
-		byte step11;
-
-		byte remainder10;
-		byte remainder8;
-		byte remainder3;
-		byte remainder7;
-		byte remainder11;
-
-		if (stepHigh == 0UL && limitHigh == 0UL)
-		{
-			step10 = (byte)(stepLow % 10UL);
-			step8 = (byte)(stepLow & 7UL);
-			step3 = (byte)(stepLow % 3UL);
-			step7 = (byte)(stepLow % 7UL);
-			step11 = (byte)(stepLow % 11UL);
-
-			remainder10 = (byte)(divisorLow % 10UL);
-			remainder8 = (byte)(divisorLow & 7UL);
-			remainder3 = (byte)(divisorLow % 3UL);
-			remainder7 = (byte)(divisorLow % 7UL);
-			remainder11 = (byte)(divisorLow % 11UL);
-
-			return CheckDivisors64(
-				prime,
-				stepLow,
-				limit.Low,
-				divisorLow,
-				decimalMask,
-				step10,
-				step8,
-				step3,
-				step7,
-				step11,
-				remainder10,
-				remainder8,
-				remainder3,
-				remainder7,
-				remainder11,
-				out processedAll,
-				out foundDivisor);
-		}
-
-		ulong divisorHigh = divisor.High;
-		step10 = (byte)((((stepHigh % 10UL) * 6UL) + (stepLow % 10UL)) % 10UL);
-		step8 = (byte)(stepLow % 8UL);
-		step3 = (byte)(((stepHigh % 3UL) + (stepLow % 3UL)) % 3UL);
-		step7 = (byte)((((stepHigh % 7UL) * 2UL) + (stepLow % 7UL)) % 7UL);
-		step11 = (byte)((((stepHigh % 11UL) * 5UL) + (stepLow % 11UL)) % 11UL);
-
-		remainder10 = (byte)((((divisorHigh % 10UL) * 6UL) + (divisorLow % 10UL)) % 10UL);
-		remainder8 = (byte)(divisorLow % 8UL);
-		remainder3 = (byte)(((divisorHigh % 3UL) + (divisorLow % 3UL)) % 3UL);
-		remainder7 = (byte)((((divisorHigh % 7UL) * 2UL) + (divisorLow % 7UL)) % 7UL);
-		remainder11 = (byte)((((divisorHigh % 11UL) * 5UL) + (divisorLow % 11UL)) % 11UL);
-
-		var gpu = PrimeOrderCalculatorAccelerator.Rent(1);
-
-		while (divisor.CompareTo(limit) <= 0)
-		{
-			bool passesSmallModuli = remainder3 != 0 && remainder7 != 0 && remainder11 != 0;
-			if (passesSmallModuli && (remainder8 == 1 || remainder8 == 7) && ((decimalMask >> remainder10) & 1) != 0)
-			{
-				ulong candidate = divisor.Low;
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
-				ulong divisorCycle;
-				// Divisors generated from 2 * k * p + 1 exceed the small-cycle snapshot when p >= 138,000,000, so the short path below never runs.
-				// if (candidate <= PerfectNumberConstants.MaxQForDivisorCycles)
-				// {
-				//     divisorCycle = cycleCache.GetCycleLength(candidate);
-				// }
-				// else
-				{
-					if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(
-							gpu,
-							candidate,
-							prime,
-							divisorData,
-							out ulong computedCycle,
-							out bool primeOrderFailed) || computedCycle == 0UL)
-					{
-						// Divisors produced by 2 * k * p + 1 always exceed PerfectNumberConstants.MaxQForDivisorCycles
-						// for the exponents scanned here, so skip the unused cache fallback and compute directly.
-						divisorCycle = MersenneDivisorCycles.CalculateCycleLength(
-							candidate,
-							divisorData,
-							skipPrimeOrderHeuristic: primeOrderFailed);
-					}
-					else
-					{
-						divisorCycle = computedCycle;
-					}
-				}
-
-				if (divisorCycle == prime)
-				{
-					// A cycle equal to the tested exponent (which is prime in this path) guarantees that the candidate divides
-					// the corresponding Mersenne number because the order of 2 modulo the divisor is exactly p.
-					foundDivisor = candidate;
-					processedAll = true;
-					PrimeOrderCalculatorAccelerator.Return(gpu);
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			divisor.Add(step);
-			remainder10 = AddMod10(remainder10, step10);
-			remainder8 = AddMod8(remainder8, step8);
-			remainder3 = AddMod3(remainder3, step3);
-			remainder7 = AddMod7(remainder7, step7);
-			remainder11 = AddMod11(remainder11, step11);
-		}
-
-		PrimeOrderCalculatorAccelerator.Return(gpu);
-		processedAll = true;
-		foundDivisor = 0UL;
-		return false;
-	}
-
-	private static bool CheckDivisors64(
-		ulong prime,
-		ulong step,
-		ulong limit,
-		ulong divisor,
-		ushort decimalMask,
-		byte step10,
-		byte step8,
-		byte step3,
-		byte step7,
-		byte step11,
-		byte remainder10,
-		byte remainder8,
-		byte remainder3,
-		byte remainder7,
-		byte remainder11,
-		out bool processedAll,
-		out ulong foundDivisor)
-	{
-		processedAll = false;
-		foundDivisor = 0UL;
-
-		bool canAdvance = step <= limit;
-		var gpu = PrimeOrderCalculatorAccelerator.Rent(1);
-		if (!canAdvance)
-		{
-			if (divisor <= limit)
-			{
-				if (remainder3 != 0 && remainder7 != 0 && remainder11 != 0 && (remainder8 == 1 || remainder8 == 7) && ((decimalMask >> remainder10) & 1) != 0)
-				{
-					MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-					ulong divisorCycle;
-					if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(
-							gpu,
-							divisor,
-							prime,
-							divisorData,
-							out ulong computedCycle,
-							out bool primeOrderFailed) || computedCycle == 0UL)
-					{
-						divisorCycle = MersenneDivisorCycles.CalculateCycleLength(
-							divisor,
-							divisorData,
-							skipPrimeOrderHeuristic: primeOrderFailed);
-					}
-					else
-					{
-						divisorCycle = computedCycle;
-					}
-
-					if (divisorCycle == prime)
-					{
-						foundDivisor = divisor;
-						processedAll = true;
-						PrimeOrderCalculatorAccelerator.Return(gpu);
-						return true;
-					}
-
-					if (divisorCycle == 0UL)
-					{
-						Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-					}
-				}
-			}
-
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		if (divisor > limit)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		ulong remainingIterations = ((limit - divisor) / step) + 1UL;
-
-		while (true)
-		{
-			bool passesSmallModuli = remainder3 != 0 && remainder7 != 0 && remainder11 != 0;
-			if (passesSmallModuli && (remainder8 == 1 || remainder8 == 7) && ((decimalMask >> remainder10) & 1) != 0)
-			{
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
-				if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(
-						gpu,
-						divisor,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					divisorCycle = MersenneDivisorCycles.CalculateCycleLength(
-						divisor,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				if (divisorCycle == prime)
-				{
-					foundDivisor = divisor;
-					processedAll = true;
-					PrimeOrderCalculatorAccelerator.Return(gpu);
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			remainingIterations--;
-			if (remainingIterations == 0UL)
-			{
-				processedAll = true;
-				foundDivisor = 0UL;
-				return false;
-			}
-
-			divisor += step;
-			remainder10 = AddMod10(remainder10, step10);
-			remainder8 = AddMod8(remainder8, step8);
-			remainder3 = AddMod3(remainder3, step3);
-			remainder7 = AddMod7(remainder7, step7);
-			remainder11 = AddMod11(remainder11, step11);
-		}
-	}
-
-	private static byte CheckDivisor(ulong prime, ulong divisorCycle, in MontgomeryDivisorData divisorData)
-	{
-		ulong residue = prime.Pow2MontgomeryModWithCycleCpu(divisorCycle, divisorData);
-		return residue == 1UL ? (byte)1 : (byte)0;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static byte AddMod3(byte value, byte delta)
-	{
-		const int Modulus = 3;
-		int sum = value + delta;
-
-		if (sum >= Modulus)
-		{
-			sum -= Modulus;
-		}
-
-		return (byte)sum;
-	}
-
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static byte AddMod7(byte value, byte delta)
-	{
-		const int Modulus = 7;
-		int sum = value + delta;
-
-		if (sum >= Modulus)
-		{
-			sum -= Modulus;
-		}
-
-		return (byte)sum;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static byte AddMod10(byte value, byte delta)
-	{
-		const int Modulus = 10;
-		int sum = value + delta;
-
-		if (sum >= Modulus)
-		{
-			sum -= Modulus;
-		}
-
-		return (byte)sum;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static byte AddMod11(byte value, byte delta)
-	{
-		const int Modulus = 11;
-		int sum = value + delta;
-
-		if (sum >= Modulus)
-		{
-			sum -= Modulus;
-		}
-
-		return (byte)sum;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static byte AddMod8(byte value, byte delta)
-	{
-		return (byte)((value + delta) & 7);
-	}
-
-	private static ulong ComputeDivisorLimitFromMaxPrime(ulong maxPrime)
-	{
-		// The by-divisor CPU configuration only supplies primes greater than 1, so the guard below never trips.
-		// if (maxPrime <= 1UL)
-		// {
-		//     return 0UL;
-		// }
-		if (maxPrime - 1UL >= 64UL)
-		{
-			return ulong.MaxValue;
-		}
-
-		return (1UL << (int)(maxPrime - 1UL)) - 1UL;
-	}
-
-	private static ulong ComputeAllowedMaxDivisor(ulong prime, ulong divisorLimit)
-	{
-		// Production by-divisor scans only handle primes, so inputs never fall below 2.
-		// if (prime <= 1UL)
-		// {
-		//     return 0UL;
-		// }
-		if (prime - 1UL >= 64UL)
-		{
-			return divisorLimit;
-		}
-
-		return Math.Min((1UL << (int)(prime - 1UL)) - 1UL, divisorLimit);
-	}
+    private ulong _divisorLimit;
+    private int _batchSize = 1_024;
+
+    [ThreadStatic]
+    private static GpuUInt128WorkSet _divisorScanGpuWorkSet;
+
+    private struct GpuUInt128WorkSet
+    {
+        public GpuUInt128 Step;
+        public GpuUInt128 Divisor;
+        public GpuUInt128 Limit;
+    }
+
+    public int BatchSize
+    {
+        get => _batchSize;
+        set => _batchSize = Math.Max(1, value);
+    }
+
+    public void ConfigureFromMaxPrime(ulong maxPrime)
+    {
+        _divisorLimit = ComputeDivisorLimitFromMaxPrime(maxPrime);
+    }
+
+    public ulong DivisorLimit
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        get
+        {
+            return _divisorLimit;
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public ulong GetAllowedMaxDivisor(ulong prime) => ComputeAllowedMaxDivisor(prime, _divisorLimit);
+
+    public bool IsPrime(ulong prime, out bool divisorsExhausted)
+    {
+        ulong allowedMax = ComputeAllowedMaxDivisor(prime, _divisorLimit);
+
+        // The CPU by-divisor run always hands us primes with enormous divisor limits, so the fallback below never executes.
+        // if (allowedMax < 3UL)
+        // {
+        //     // EvenPerfectBitScanner routes primes below the small-divisor cutoff to the GPU path, so the CPU path still sees
+        //     // trivial candidates during targeted tests. Short-circuit here to keep those runs aligned with the production flow.
+        //     divisorsExhausted = true;
+        //     return true;
+        // }
+
+        bool processedAll;
+
+        bool composite = CheckDivisors(
+            prime,
+            allowedMax,
+            out processedAll);
+
+        if (composite)
+        {
+            divisorsExhausted = true;
+            return false;
+        }
+
+        divisorsExhausted = processedAll || composite;
+        return true;
+    }
+
+    public void PrepareCandidates(in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
+    {
+        ulong divisorLimit = _divisorLimit;
+        int length = primes.Length;
+        for (int index = 0; index < length; index++)
+        {
+            allowedMaxValues[index] = ComputeAllowedMaxDivisor(primes[index], divisorLimit);
+        }
+    }
+
+    public IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession()
+    {
+        MersenneCpuDivisorScanSession? session = ThreadStaticPools.RentMersenneCpuDivisorSession();
+        if (session is not null)
+        {
+            return session;
+        }
+
+        return new MersenneCpuDivisorScanSession();
+    }
+
+    private bool CheckDivisors(
+        ulong prime,
+        ulong allowedMax,
+        out bool processedAll)
+    {
+        processedAll = false;
+
+        // The EvenPerfectBitScanner feeds primes >= 138,000,000 here, so allowedMax >= 3 in production runs.
+        // Keeping the guard commented out documents the reasoning for benchmarks and tests.
+        // if (allowedMax < 3UL)
+        // {
+        //     return false;
+        // }
+
+        ref GpuUInt128WorkSet workSet = ref _divisorScanGpuWorkSet;
+
+        ref GpuUInt128 step = ref workSet.Step;
+        step.High = 0UL;
+        step.Low = prime;
+        step.ShiftLeft(1);
+
+        ref GpuUInt128 limit = ref workSet.Limit;
+        limit.High = 0UL;
+        limit.Low = allowedMax;
+
+        ref GpuUInt128 divisor = ref workSet.Divisor;
+        divisor.High = step.High;
+        divisor.Low = step.Low;
+        divisor.Add(1UL);
+        if (divisor.CompareTo(limit) > 0)
+        {
+            processedAll = true;
+            return false;
+        }
+
+        // Intentionally recomputes factorizations without a per-thread cache.
+        // The previous factor cache recorded virtually no hits and only slowed down the scan.
+        DivisorCycleCache cycleCache = DivisorCycleCache.Shared;
+
+        ulong stepHigh = step.High;
+        ulong stepLow = step.Low;
+        byte step10 = (byte)((((stepHigh % 10UL) * 6UL) + (stepLow % 10UL)) % 10UL);
+        byte step8 = (byte)(stepLow % 8UL);
+        byte step5 = (byte)(((stepHigh % 5UL) + (stepLow % 5UL)) % 5UL);
+        byte step3 = (byte)(((stepHigh % 3UL) + (stepLow % 3UL)) % 3UL);
+        byte step7 = (byte)((((stepHigh % 7UL) * 2UL) + (stepLow % 7UL)) % 7UL);
+        byte step11 = (byte)((((stepHigh % 11UL) * 5UL) + (stepLow % 11UL)) % 11UL);
+
+        ulong divisorHigh = divisor.High;
+        ulong divisorLow = divisor.Low;
+        byte remainder10 = (byte)((((divisorHigh % 10UL) * 6UL) + (divisorLow % 10UL)) % 10UL);
+        byte remainder8 = (byte)(divisorLow % 8UL);
+        byte remainder5 = (byte)(((divisorHigh % 5UL) + (divisorLow % 5UL)) % 5UL);
+        byte remainder3 = (byte)(((divisorHigh % 3UL) + (divisorLow % 3UL)) % 3UL);
+        byte remainder7 = (byte)((((divisorHigh % 7UL) * 2UL) + (divisorLow % 7UL)) % 7UL);
+        byte remainder11 = (byte)((((divisorHigh % 11UL) * 5UL) + (divisorLow % 11UL)) % 11UL);
+
+        // Keep the divisibility filters aligned with the divisor-cycle generator so the
+        // CPU path never requests cycles that were skipped during cache creation.
+        LastDigit lastDigit = (prime & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
+        ushort decimalMask = DivisorGenerator.GetDecimalMask(lastDigit);
+
+        while (divisor.CompareTo(limit) <= 0)
+        {
+            ulong candidate = divisor.Low;
+
+            bool admissible = ((decimalMask >> remainder10) & 1) != 0
+                && (remainder8 == 1 || remainder8 == 7)
+                && remainder3 != 0
+                && remainder5 != 0
+                && remainder7 != 0
+                && remainder11 != 0;
+
+            if (admissible)
+            {
+                MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
+                ulong divisorCycle;
+                // Divisors generated from 2 * k * p + 1 exceed the small-cycle snapshot when p >= 138,000,000, so the short path below never runs.
+                // if (candidate <= PerfectNumberConstants.MaxQForDivisorCycles)
+                // {
+                //     divisorCycle = cycleCache.GetCycleLength(candidate);
+                // }
+                // else
+                {
+                    if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(
+                            candidate,
+                            prime,
+                            divisorData,
+                            out ulong computedCycle,
+                            out bool primeOrderFailed) || computedCycle == 0UL)
+                    {
+                        // Divisors produced by 2 * k * p + 1 always exceed PerfectNumberConstants.MaxQForDivisorCycles
+                        // for the exponents scanned here, so skip the unused cache fallback and compute directly.
+                        divisorCycle = MersenneDivisorCycles.CalculateCycleLength(
+                            candidate,
+                            divisorData,
+                            skipPrimeOrderHeuristic: primeOrderFailed);
+                    }
+                    else
+                    {
+                        divisorCycle = computedCycle;
+                    }
+                }
+
+                if (divisorCycle == prime)
+                {
+                    // A cycle equal to the tested exponent (which is prime in this path) guarantees that the candidate divides
+                    // the corresponding Mersenne number because the order of 2 modulo the divisor is exactly p.
+                    processedAll = true;
+                    return true;
+                }
+
+                if (divisorCycle == 0UL)
+                {
+                    Console.WriteLine($"Divisor cycle was not calculated for {prime}");
+                }
+            }
+
+            divisor.Add(step);
+            remainder10 = AddMod(remainder10, step10, (byte)10);
+            remainder8 = AddMod8(remainder8, step8);
+            remainder5 = AddMod(remainder5, step5, (byte)5);
+            remainder3 = AddMod(remainder3, step3, (byte)3);
+            remainder7 = AddMod(remainder7, step7, (byte)7);
+            remainder11 = AddMod(remainder11, step11, (byte)11);
+        }
+
+        processedAll = divisor.CompareTo(limit) > 0;
+        return false;
+    }
+
+    private static byte CheckDivisor(ulong prime, ulong divisorCycle, in MontgomeryDivisorData divisorData)
+    {
+        ulong residue = prime.Pow2MontgomeryModWithCycleCpu(divisorCycle, divisorData);
+        return residue == 1UL ? (byte)1 : (byte)0;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static byte AddMod(byte value, byte delta, byte modulus)
+    {
+        int sum = value + delta;
+
+        if (sum >= modulus)
+        {
+            sum -= modulus;
+        }
+
+        return (byte)sum;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static byte AddMod8(byte value, byte delta)
+    {
+        return (byte)((value + delta) & 7);
+    }
+
+    private static ulong ComputeDivisorLimitFromMaxPrime(ulong maxPrime)
+    {
+        // The by-divisor CPU configuration only supplies primes greater than 1, so the guard below never trips.
+        // if (maxPrime <= 1UL)
+        // {
+        //     return 0UL;
+        // }
+        if (maxPrime - 1UL >= 64UL)
+        {
+            return ulong.MaxValue;
+        }
+
+        return (1UL << (int)(maxPrime - 1UL)) - 1UL;
+    }
+
+    private static ulong ComputeAllowedMaxDivisor(ulong prime, ulong divisorLimit)
+    {
+        // Production by-divisor scans only handle primes, so inputs never fall below 2.
+        // if (prime <= 1UL)
+        // {
+        //     return 0UL;
+        // }
+        if (prime - 1UL >= 64UL)
+        {
+            return divisorLimit;
+        }
+
+        return Math.Min((1UL << (int)(prime - 1UL)) - 1UL, divisorLimit);
+    }
 
 
 }

PerfectNumbers.Core/DeterministicRandom.cs

@@ -1,6 +1,6 @@
-namespace PerfectNumbers.Core.Cpu;
+namespace PerfectNumbers.Core;
 
-internal static class DeterministicRandomCpu
+internal static class DeterministicRandom
 {
     [ThreadStatic]
     private static ulong s_threadState;

PerfectNumbers.Core/DivisorCycleCache.cs

@@ -1,377 +1,331 @@
+using System.Buffers;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using ILGPU;
 using ILGPU.Runtime;
 using PerfectNumbers.Core.Gpu;
-using PerfectNumbers.Core.Gpu.Accelerators;
 
 namespace PerfectNumbers.Core;
 
 public sealed class DivisorCycleCache
 {
-	private const byte ByteZero = 0;
-	private const byte ByteOne = 1;
-	private const int StackBufferThreshold = 128;
-	private readonly Accelerator _accelerator;
-	private readonly int _acceleratorIndex;
-	private readonly Action<AcceleratorStream, Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>> _gpuKernel;
-	private volatile ulong[] _snapshot;
-	private volatile bool _useGpuGeneration = true;
-	private readonly int _divisorCyclesBatchSize;
-	private static int _sharedDivisorCyclesBatchSize = GpuConstants.GpuCycleStepsPerInvocation;
+    private const byte ByteZero = 0;
+    private const byte ByteOne = 1;
+    private const int StackBufferThreshold = 128;
 
-	private const int CycleCacheTrackingLimit = 500_000;
-	private static readonly HashSet<ulong> CycleCacheTrackedDivisors = new();
-	private static readonly object CycleCacheTrackingLock = new();
-	private static ulong CycleCacheHitCount;
-	private static bool CycleCacheTrackingDisabled;
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>> _gpuKernelCache = new(AcceleratorReferenceComparer.Instance);
+    private volatile ulong[] _snapshot;
+    private volatile bool _useGpuGeneration = true;
+    private readonly int _divisorCyclesBatchSize;
+    private static int _sharedDivisorCyclesBatchSize = GpuConstants.GpuCycleStepsPerInvocation;
 
-	public static void SetDivisorCyclesBatchSize(int divisorCyclesBatchSize)
-	{
-		_sharedDivisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
-	}
+    private const int CycleCacheTrackingLimit = 500_000;
+    private static readonly HashSet<ulong> CycleCacheTrackedDivisors = new();
+    private static readonly object CycleCacheTrackingLock = new();
+    private static ulong CycleCacheHitCount;
+    private static bool CycleCacheTrackingDisabled;
 
-	public static DivisorCycleCache Shared { get; } = new DivisorCycleCache(_sharedDivisorCyclesBatchSize);
+    public static void SetDivisorCyclesBatchSize(int divisorCyclesBatchSize)
+    {
+        _sharedDivisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
+    }
 
-	public int PreferredBatchSize => _divisorCyclesBatchSize;
+    public static DivisorCycleCache Shared { get; } = new DivisorCycleCache(_sharedDivisorCyclesBatchSize);
 
-	// private static readonly Accelerator[] _accelerators;
+    public int PreferredBatchSize => _divisorCyclesBatchSize;
 
-	private DivisorCycleCache(int divisorCyclesBatchSize)
-	{
-		_divisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
-		var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		_acceleratorIndex = acceleratorIndex;
-		Accelerator accelerator = AcceleratorPool.Shared.Accelerators[acceleratorIndex];
-		_accelerator = accelerator;
-		_gpuKernel = LoadKernel(accelerator);
-		_snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
-	}
+    private DivisorCycleCache(int divisorCyclesBatchSize)
+    {
+        _divisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
+        _snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
+    }
 
-	public void ConfigureGeneratorDevice(bool useGpu)
-	{
-		_useGpuGeneration = useGpu;
-	}
+    public void ConfigureGeneratorDevice(bool useGpu)
+    {
+        _useGpuGeneration = useGpu;
+    }
 
-	public void RefreshSnapshot()
-	{
-		_snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
-	}
+    public void RefreshSnapshot()
+    {
+        _snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
+    }
 
-	public ulong GetCycleLength(ulong divisor, bool skipPrimeOrderHeuristic = false)
-	{
-		if (!skipPrimeOrderHeuristic)
-		{
-			Span<ulong> result = stackalloc ulong[1];
-			ReadOnlySpan<ulong> singleDivisor = stackalloc ulong[1] { divisor };
-			GetCycleLengths(singleDivisor, result);
-			return result[0];
-		}
+    public ulong GetCycleLength(ulong divisor, bool skipPrimeOrderHeuristic = false)
+    {
+        if (!skipPrimeOrderHeuristic)
+        {
+            Span<ulong> result = stackalloc ulong[1];
+            ReadOnlySpan<ulong> singleDivisor = stackalloc ulong[1] { divisor };
+            GetCycleLengths(singleDivisor, result);
+            return result[0];
+        }
 
-		// The skipPrimeOrderHeuristic path is only used for divisors produced by the CPU by-divisor scanner,
-		// which always generates values greater than one. Keep this guard disabled here to avoid repeating the
-		// validation already performed by the general GetCycleLengths path.
-		// if (divisor <= 1UL)
-		// {
-		//     throw new InvalidDataException("Divisor must be > 1");
-		// }
+        // The skipPrimeOrderHeuristic path is only used for divisors produced by the CPU by-divisor scanner,
+        // which always generates values greater than one. Keep this guard disabled here to avoid repeating the
+        // validation already performed by the general GetCycleLengths path.
+        // if (divisor <= 1UL)
+        // {
+        //     throw new InvalidDataException("Divisor must be > 1");
+        // }
 
-		ulong[] snapshot = _snapshot;
-		if (divisor < (ulong)snapshot.Length)
-		{
-			ulong cached = snapshot[divisor];
-			if (cached == 0UL)
-			{
-				throw new InvalidDataException($"Divisor cycle is missing for {divisor}");
-			}
+        ulong[] snapshot = _snapshot;
+        if (divisor < (ulong)snapshot.Length)
+        {
+            ulong cached = snapshot[divisor];
+            if (cached == 0UL)
+            {
+                throw new InvalidDataException($"Divisor cycle is missing for {divisor}");
+            }
 
-			return cached;
-		}
+            // ObserveCycleCacheDivisor(divisor);
+            return cached;
+        }
 
-		MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-		return MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData, skipPrimeOrderHeuristic: true);
-	}
+        MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
+        return MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData, skipPrimeOrderHeuristic: true);
+    }
 
-	public void GetCycleLengths(ReadOnlySpan<ulong> divisors, Span<ulong> cycles)
-	{
-		ulong[] snapshot = _snapshot;
-		int length = divisors.Length;
-		int[]? rentedMissing = null;
-		Span<int> missingBuffer = length <= StackBufferThreshold
-			? stackalloc int[length]
-			: new Span<int>(rentedMissing = ThreadStaticPools.IntPool.Rent(length), 0, length);
+    public void GetCycleLengths(ReadOnlySpan<ulong> divisors, Span<ulong> cycles)
+    {
+        ulong[] snapshot = _snapshot;
+        int length = divisors.Length;
+        int[]? rentedMissing = null;
+        Span<int> missingBuffer = length <= StackBufferThreshold
+            ? stackalloc int[length]
+            : new Span<int>(rentedMissing = ArrayPool<int>.Shared.Rent(length), 0, length);
 
-		int missingCount = 0;
+        int missingCount = 0;
 
-		for (int i = 0; i < length; i++)
-		{
-			ulong divisor = divisors[i];
-			if (divisor <= 1UL)
-			{
-				throw new InvalidDataException("Divisor must be > 1");
-			}
+        for (int i = 0; i < length; i++)
+        {
+            ulong divisor = divisors[i];
+            if (divisor <= 1UL)
+            {
+                throw new InvalidDataException("Divisor must be > 1");
+            }
 
-			if (divisor < (ulong)snapshot.Length)
-			{
-				ulong cached = snapshot[divisor];
-				if (cached == 0UL)
-				{
-					throw new InvalidDataException($"Divisor cycle is missing for {divisor}");
-				}
+            if (divisor < (ulong)snapshot.Length)
+            {
+                ulong cached = snapshot[divisor];
+                if (cached == 0UL)
+                {
+                    throw new InvalidDataException($"Divisor cycle is missing for {divisor}");
+                }
 
-				cycles[i] = cached;
-			}
-			else
-			{
-				missingBuffer[missingCount++] = i;
-			}
-		}
+                // ObserveCycleCacheDivisor(divisor);
+                cycles[i] = cached;
+            }
+            else
+            {
+                missingBuffer[missingCount++] = i;
+            }
+        }
 
-		if (missingCount != 0)
-		{
-			ReadOnlySpan<int> missingIndices = missingBuffer[..missingCount];
-			if (_useGpuGeneration)
-			{
-				ComputeCyclesGpu(divisors, cycles, missingIndices);
-			}
-			else
-			{
-				ComputeCyclesCpu(divisors, cycles, missingIndices);
-			}
-		}
+        if (missingCount != 0)
+        {
+            ReadOnlySpan<int> missingIndices = missingBuffer[..missingCount];
+            if (_useGpuGeneration)
+            {
+                ComputeCyclesGpu(divisors, cycles, missingIndices);
+            }
+            else
+            {
+                ComputeCyclesCpu(divisors, cycles, missingIndices);
+            }
+        }
 
-		if (rentedMissing is not null)
-		{
-			ThreadStaticPools.IntPool.Return(rentedMissing, clearArray: false);
-		}
-	}
+        if (rentedMissing is not null)
+        {
+            ArrayPool<int>.Shared.Return(rentedMissing, clearArray: false);
+        }
+    }
 
-	private static void ObserveCycleCacheDivisor(ulong divisor)
-	{
-		bool logHit = false;
-		ulong hitNumber = 0UL;
-		bool trackingDisabledNow = false;
+    private static void ObserveCycleCacheDivisor(ulong divisor)
+    {
+        bool logHit = false;
+        ulong hitNumber = 0UL;
+        bool trackingDisabledNow = false;
 
-		lock (CycleCacheTrackingLock)
-		{
-			if (CycleCacheTrackingDisabled)
-			{
-				return;
-			}
+        lock (CycleCacheTrackingLock)
+        {
+            if (CycleCacheTrackingDisabled)
+            {
+                return;
+            }
 
-			if (!CycleCacheTrackedDivisors.Add(divisor))
-			{
-				CycleCacheHitCount++;
-				hitNumber = CycleCacheHitCount;
-				logHit = true;
-			}
-			else if (CycleCacheTrackedDivisors.Count >= CycleCacheTrackingLimit)
-			{
-				CycleCacheTrackingDisabled = true;
-				CycleCacheTrackedDivisors.Clear();
-				trackingDisabledNow = true;
-			}
-		}
+            if (!CycleCacheTrackedDivisors.Add(divisor))
+            {
+                CycleCacheHitCount++;
+                hitNumber = CycleCacheHitCount;
+                logHit = true;
+            }
+            else if (CycleCacheTrackedDivisors.Count >= CycleCacheTrackingLimit)
+            {
+                CycleCacheTrackingDisabled = true;
+                CycleCacheTrackedDivisors.Clear();
+                trackingDisabledNow = true;
+            }
+        }
 
-		if (logHit)
-		{
-			Console.WriteLine($"Cycle cache hit for divisor {divisor} ({hitNumber})");
-		}
-		else if (trackingDisabledNow)
-		{
-			Console.WriteLine("Cycle cache hit tracking disabled after exceeding the tracking limit.");
-		}
-	}
+        if (logHit)
+        {
+            Console.WriteLine($"Cycle cache hit for divisor {divisor} ({hitNumber})");
+        }
+        else if (trackingDisabledNow)
+        {
+            Console.WriteLine("Cycle cache hit tracking disabled after exceeding the tracking limit.");
+        }
+    }
 
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static void ComputeCyclesCpu(ReadOnlySpan<ulong> divisors, Span<ulong> cycles, ReadOnlySpan<int> indices)
-	{
-		for (int i = 0; i < indices.Length; i++)
-		{
-			int targetIndex = indices[i];
-			ulong divisor = divisors[targetIndex];
-			MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-			cycles[targetIndex] = MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData);
-		}
-	}
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void ComputeCyclesCpu(ReadOnlySpan<ulong> divisors, Span<ulong> cycles, ReadOnlySpan<int> indices)
+    {
+        for (int i = 0; i < indices.Length; i++)
+        {
+            int targetIndex = indices[i];
+            ulong divisor = divisors[targetIndex];
+            MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
+            cycles[targetIndex] = MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData);
+        }
+    }
 
-	private void ComputeCyclesGpu(ReadOnlySpan<ulong> divisors, Span<ulong> cycles, ReadOnlySpan<int> indices)
-	{
-		int count = indices.Length;
-		ulong[]? rentedDivisors = null;
-		Span<ulong> workDivisors = count <= StackBufferThreshold
-			? stackalloc ulong[count]
-			: new Span<ulong>(rentedDivisors = ThreadStaticPools.UlongPool.Rent(count), 0, count);
+    private void ComputeCyclesGpu(ReadOnlySpan<ulong> divisors, Span<ulong> cycles, ReadOnlySpan<int> indices)
+    {
+        int count = indices.Length;
+        ulong[]? rentedDivisors = null;
+        Span<ulong> workDivisors = count <= StackBufferThreshold
+            ? stackalloc ulong[count]
+            : new Span<ulong>(rentedDivisors = ArrayPool<ulong>.Shared.Rent(count), 0, count);
 
-		ulong[]? rentedResults = null;
-		Span<ulong> workResults = count <= StackBufferThreshold
-			? stackalloc ulong[count]
-			: new Span<ulong>(rentedResults = ThreadStaticPools.UlongPool.Rent(count), 0, count);
+        ulong[]? rentedResults = null;
+        Span<ulong> workResults = count <= StackBufferThreshold
+            ? stackalloc ulong[count]
+            : new Span<ulong>(rentedResults = ArrayPool<ulong>.Shared.Rent(count), 0, count);
 
-		for (int i = 0; i < count; i++)
-		{
-			workDivisors[i] = divisors[indices[i]];
-		}
+        for (int i = 0; i < count; i++)
+        {
+            workDivisors[i] = divisors[indices[i]];
+        }
 
-		ComputeCyclesGpuCore(workDivisors, workResults);
+        ComputeCyclesGpuCore(workDivisors, workResults);
 
-		for (int i = 0; i < count; i++)
-		{
-			cycles[indices[i]] = workResults[i];
-		}
+        for (int i = 0; i < count; i++)
+        {
+            cycles[indices[i]] = workResults[i];
+        }
 
-		if (rentedDivisors is not null)
-		{
-			ThreadStaticPools.UlongPool.Return(rentedDivisors, clearArray: false);
-			ThreadStaticPools.UlongPool.Return(rentedResults!, clearArray: false);
-		}
-	}
+        if (rentedDivisors is not null)
+        {
+            ArrayPool<ulong>.Shared.Return(rentedDivisors, clearArray: false);
+            ArrayPool<ulong>.Shared.Return(rentedResults!, clearArray: false);
+        }
+    }
 
-	private const int DefaultCapacity = 128;
+    private void ComputeCyclesGpuCore(ReadOnlySpan<ulong> divisors, Span<ulong> destination)
+    {
+        int length = divisors.Length;
+        var gpuLease = GpuKernelPool.GetKernel(useGpuOrder: true);
+        var execution = gpuLease.EnterExecutionScope();
 
-	[ThreadStatic]
-	private static MemoryBuffer1D<ulong, Stride1D.Dense>? divisorBuffer;
+        Accelerator accelerator = gpuLease.Accelerator;
+        var kernel = _gpuKernelCache.GetOrAdd(accelerator, LoadKernel);
 
-	[ThreadStatic]
-	private static MemoryBuffer1D<ulong, Stride1D.Dense>? powBuffer;
+        using MemoryBuffer1D<ulong, Stride1D.Dense> divisorBuffer = accelerator.Allocate1D<ulong>(length);
+        using MemoryBuffer1D<ulong, Stride1D.Dense> powBuffer = accelerator.Allocate1D<ulong>(length);
+        using MemoryBuffer1D<ulong, Stride1D.Dense> orderBuffer = accelerator.Allocate1D<ulong>(length);
+        using MemoryBuffer1D<ulong, Stride1D.Dense> resultBuffer = accelerator.Allocate1D<ulong>(length);
+        using MemoryBuffer1D<byte, Stride1D.Dense> statusBuffer = accelerator.Allocate1D<byte>(length);
 
-	[ThreadStatic]
-	private static MemoryBuffer1D<ulong, Stride1D.Dense>? orderBuffer;
+        ulong[]? rentedPow = null;
+        Span<ulong> powSpan = length <= StackBufferThreshold
+            ? stackalloc ulong[length]
+            : new Span<ulong>(rentedPow = ArrayPool<ulong>.Shared.Rent(length), 0, length);
 
-	[ThreadStatic]
-	private static MemoryBuffer1D<ulong, Stride1D.Dense>? resultBuffer;
+        ulong[]? rentedOrder = null;
+        Span<ulong> orderSpan = length <= StackBufferThreshold
+            ? stackalloc ulong[length]
+            : new Span<ulong>(rentedOrder = ArrayPool<ulong>.Shared.Rent(length), 0, length);
 
-	[ThreadStatic]
-	private static MemoryBuffer1D<byte, Stride1D.Dense>? statusBuffer;
+        ulong[]? rentedResult = null;
+        Span<ulong> resultSpan = length <= StackBufferThreshold
+            ? stackalloc ulong[length]
+            : new Span<ulong>(rentedResult = ArrayPool<ulong>.Shared.Rent(length), 0, length);
 
-	private void EnsureCapacity(int requiredCapacity)
-	{
-		if (requiredCapacity <= (divisorBuffer?.Length ?? 0))
-		{
-			return;
-		}
+        byte[]? rentedStatus = null;
+        Span<byte> statusSpan = length <= StackBufferThreshold
+            ? stackalloc byte[length]
+            : new Span<byte>(rentedStatus = ArrayPool<byte>.Shared.Rent(length), 0, length);
 
-		if (divisorBuffer != null)
-		{
-			divisorBuffer.Dispose();
-			powBuffer!.Dispose();
-			orderBuffer!.Dispose();
-			resultBuffer!.Dispose();
-			statusBuffer!.Dispose();
-		}
+        ref ulong divisorRef = ref MemoryMarshal.GetReference(divisors);
+        divisorBuffer.View.CopyFromCPU(ref divisorRef, length);
 
-		Accelerator accelerator = _accelerator;
-		lock(accelerator)
-		{
-			divisorBuffer = accelerator.Allocate1D<ulong>(requiredCapacity);
-			powBuffer = accelerator.Allocate1D<ulong>(requiredCapacity);
-			orderBuffer = accelerator.Allocate1D<ulong>(requiredCapacity);
-			resultBuffer = accelerator.Allocate1D<ulong>(requiredCapacity);
-			statusBuffer = accelerator.Allocate1D<byte>(requiredCapacity);
-		}
-	}
+        for (int i = 0; i < length; i++)
+        {
+            ulong divisor = divisors[i];
+            ulong initialPow = 2UL;
+            if (initialPow >= divisor)
+            {
+                initialPow -= divisor;
+            }
 
-	private void ComputeCyclesGpuCore(ReadOnlySpan<ulong> divisors, Span<ulong> destination)
-	{
-		int length = divisors.Length;
+            powSpan[i] = initialPow;
+            orderSpan[i] = 1UL;
+            resultSpan[i] = 0UL;
+            statusSpan[i] = ByteZero;
+        }
 
-		EnsureCapacity(length);
+        powBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(powSpan), length);
+        orderBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(orderSpan), length);
+        resultBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(resultSpan), length);
+        statusBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(statusSpan), length);
 
-		ulong[]? rentedPow = null;
-		Span<ulong> powSpan = length <= StackBufferThreshold
-			? stackalloc ulong[length]
-			: new Span<ulong>(rentedPow = ThreadStaticPools.UlongPool.Rent(length), 0, length);
+        int pending;
+        do
+        {
+            kernel(length, _divisorCyclesBatchSize, divisorBuffer.View, powBuffer.View, orderBuffer.View, resultBuffer.View, statusBuffer.View);
+            accelerator.Synchronize();
 
-		ulong[]? rentedOrder = null;
-		Span<ulong> orderSpan = length <= StackBufferThreshold
-			? stackalloc ulong[length]
-			: new Span<ulong>(rentedOrder = ThreadStaticPools.UlongPool.Rent(length), 0, length);
+            statusBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(statusSpan), length);
+            pending = 0;
+            for (int i = 0; i < length; i++)
+            {
+                if (statusSpan[i] == ByteZero)
+                {
+                    pending++;
+                }
+            }
+        }
+        while (pending > 0);
 
-		ulong[]? rentedResult = null;
-		Span<ulong> resultSpan = length <= StackBufferThreshold
-			? stackalloc ulong[length]
-			: new Span<ulong>(rentedResult = ThreadStaticPools.UlongPool.Rent(length), 0, length);
+        resultBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(resultSpan), length);
+        resultSpan.CopyTo(destination);
+        if (rentedPow is not null)
+        {
+            ArrayPool<ulong>.Shared.Return(rentedPow, clearArray: false);
+            ArrayPool<ulong>.Shared.Return(rentedOrder!, clearArray: false);
+            ArrayPool<ulong>.Shared.Return(rentedResult!, clearArray: false);
+            ArrayPool<byte>.Shared.Return(rentedStatus!, clearArray: false);
+        }
 
-		byte[]? rentedStatus = null;
-		Span<byte> statusSpan = length <= StackBufferThreshold
-			? stackalloc byte[length]
-			: new Span<byte>(rentedStatus = ThreadStaticPools.BytePool.Rent(length), 0, length);
+        execution.Dispose();
+        gpuLease.Dispose();
+    }
 
-		for (int i = 0; i < length; i++)
-		{
-			ulong divisor = divisors[i];
-			ulong initialPow = 2UL;
-			if (initialPow >= divisor)
-			{
-				initialPow -= divisor;
-			}
+    private static Action<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>> LoadKernel(Accelerator accelerator)
+    {
+        return accelerator.LoadAutoGroupedStreamKernel<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>(DivisorCycleKernels.GpuAdvanceDivisorCyclesKernel);
+    }
 
-			powSpan[i] = initialPow;
-			orderSpan[i] = 1UL;
-			resultSpan[i] = 0UL;
-			statusSpan[i] = ByteZero;
-		}
+    private sealed class AcceleratorReferenceComparer : IEqualityComparer<Accelerator>
+    {
+        internal static AcceleratorReferenceComparer Instance { get; } = new();
 
-		// GpuPrimeWorkLimiter.Acquire();
-		int pending;
-		var kernel = _gpuKernel;
-		var acceleratorIndex = _acceleratorIndex;
-		var stream = AcceleratorStreamPool.Rent(acceleratorIndex);
+        public bool Equals(Accelerator? x, Accelerator? y) => ReferenceEquals(x, y);
 
-		divisorBuffer!.View.CopyFromCPU(stream, divisors);
-		powBuffer!.View.CopyFromCPU(stream, powSpan);
-		orderBuffer!.View.CopyFromCPU(stream, orderSpan);
-		resultBuffer!.View.CopyFromCPU(stream, resultSpan);
-		statusBuffer!.View.CopyFromCPU(stream, statusSpan);
-
-		do
-		{
-			kernel(stream, length, _divisorCyclesBatchSize, divisorBuffer.View, powBuffer.View, orderBuffer.View, resultBuffer.View, statusBuffer.View);
-
-			statusBuffer.View.CopyToCPU(stream, statusSpan);
-			stream.Synchronize();
-
-			pending = 0;
-			for (int i = 0; i < length; i++)
-			{
-				if (statusSpan[i] == ByteZero)
-				{
-					pending++;
-				}
-			}
-		}
-		while (pending > 0);
-
-		resultBuffer.View.CopyToCPU(stream, resultSpan);
-		stream.Synchronize();
-		AcceleratorStreamPool.Return(acceleratorIndex, stream);
-
-		resultSpan.CopyTo(destination);
-		if (rentedPow is not null)
-		{
-			ThreadStaticPools.UlongPool.Return(rentedPow, clearArray: false);
-			ThreadStaticPools.UlongPool.Return(rentedOrder!, clearArray: false);
-			ThreadStaticPools.UlongPool.Return(rentedResult!, clearArray: false);
-			ThreadStaticPools.BytePool.Return(rentedStatus!, clearArray: false);
-		}
-
-		// GpuPrimeWorkLimiter.Release();
-	}
-
-	private static Action<AcceleratorStream, Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>> LoadKernel(Accelerator accelerator)
-	{
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>(DivisorCycleKernels.GpuAdvanceDivisorCyclesKernel);
-		var kernel = KernelUtil.GetKernel(loaded);
-		return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>>();
-	}
-
-	private sealed class AcceleratorReferenceComparer : IEqualityComparer<Accelerator>
-	{
-		internal static AcceleratorReferenceComparer Instance { get; } = new();
-
-		public bool Equals(Accelerator? x, Accelerator? y) => ReferenceEquals(x, y);
-
-		public int GetHashCode(Accelerator obj) => RuntimeHelpers.GetHashCode(obj);
-	}
+        public int GetHashCode(Accelerator obj) => RuntimeHelpers.GetHashCode(obj);
+    }
 }
 
 

PerfectNumbers.Core/DivisorGenerator.cs

@@ -4,272 +4,40 @@ namespace PerfectNumbers.Core;
 
 internal static class DivisorGenerator
 {
-    public static readonly uint[] SmallPrimes;
-    public static readonly ulong[] SmallPrimesPow2;
-    public static readonly uint[] SmallPrimesLastOne;
-    public static readonly ulong[] SmallPrimesPow2LastOne;
-    public static readonly uint[] SmallPrimesLastSeven;
-    public static readonly ulong[] SmallPrimesPow2LastSeven;
-    public static readonly uint[] SmallPrimesLastThree;
-    public static readonly ulong[] SmallPrimesPow2LastThree;
-    public static readonly uint[] SmallPrimesLastNine;
-    public static readonly ulong[] SmallPrimesPow2LastNine;
-    public static readonly uint[] SmallPrimesLastOneWithoutLastThree;
-    public static readonly ulong[] SmallPrimesPow2LastOneWithoutLastThree;
-    public static readonly uint[] SmallPrimesLastSevenWithoutLastThree;
-    public static readonly ulong[] SmallPrimesPow2LastSevenWithoutLastThree;
-    public static readonly uint[] SmallPrimesLastNineWithoutLastThree;
-    public static readonly ulong[] SmallPrimesPow2LastNineWithoutLastThree;
-
     private const ushort DecimalMaskWhenLastIsSeven = (1 << 3) | (1 << 7) | (1 << 9);
-    private const ushort DecimalMaskWhenLastIsThree = (1 << 1) | (1 << 3) | (1 << 7) | (1 << 9);
-    private const ushort DecimalMaskWhenLastIsNine = (1 << 1) | (1 << 3) | (1 << 7) | (1 << 9);
     private const ushort DecimalMaskOtherwise = (1 << 1) | (1 << 3) | (1 << 9);
 
-    static DivisorGenerator()
-    {
-        BuildSmallPrimes(
-            out SmallPrimes,
-            out SmallPrimesPow2,
-            out SmallPrimesLastOne,
-            out SmallPrimesPow2LastOne,
-            out SmallPrimesLastSeven,
-            out SmallPrimesPow2LastSeven,
-            out SmallPrimesLastThree,
-            out SmallPrimesPow2LastThree,
-            out SmallPrimesLastNine,
-            out SmallPrimesPow2LastNine,
-            out SmallPrimesLastOneWithoutLastThree,
-            out SmallPrimesPow2LastOneWithoutLastThree,
-            out SmallPrimesLastSevenWithoutLastThree,
-            out SmallPrimesPow2LastSevenWithoutLastThree,
-            out SmallPrimesLastNineWithoutLastThree,
-            out SmallPrimesPow2LastNineWithoutLastThree);
-    }
-
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static ushort GetDecimalMask(LastDigit lastDigit)
     {
-        return lastDigit switch
-        {
-            LastDigit.Seven => DecimalMaskWhenLastIsSeven,
-            LastDigit.Three => DecimalMaskWhenLastIsThree,
-            LastDigit.Nine => DecimalMaskWhenLastIsNine,
-            _ => DecimalMaskOtherwise,
-        };
+        return lastDigit == LastDigit.Seven ? DecimalMaskWhenLastIsSeven : DecimalMaskOtherwise;
     }
 
-    private static void BuildSmallPrimes(
-        out uint[] all,
-        out ulong[] allPow2,
-        out uint[] lastOne,
-        out ulong[] lastOnePow2,
-        out uint[] lastSeven,
-        out ulong[] lastSevenPow2,
-        out uint[] lastThree,
-        out ulong[] lastThreePow2,
-        out uint[] lastNine,
-        out ulong[] lastNinePow2,
-        out uint[] lastOneWithoutThree,
-        out ulong[] lastOneWithoutThreePow2,
-        out uint[] lastSevenWithoutThree,
-        out ulong[] lastSevenWithoutThreePow2,
-        out uint[] lastNineWithoutThree,
-        out ulong[] lastNineWithoutThreePow2)
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool IsValidDivisor(
+        byte remainder10,
+        byte remainder8,
+        byte remainder3,
+        byte remainder5,
+        byte remainder7,
+        byte remainder11,
+        ushort decimalMask)
     {
-        uint target = PerfectNumberConstants.PrimesLimit;
-        int targetInt = checked((int)target);
-        all = new uint[targetInt];
-        allPow2 = new ulong[targetInt];
-        lastOne = new uint[targetInt];
-        lastOnePow2 = new ulong[targetInt];
-        lastSeven = new uint[targetInt];
-        lastSevenPow2 = new ulong[targetInt];
-        lastThree = new uint[targetInt];
-        lastThreePow2 = new ulong[targetInt];
-        lastNine = new uint[targetInt];
-        lastNinePow2 = new ulong[targetInt];
-
-        List<uint> primes = new(targetInt * 4 / 3 + 16);
-        List<uint> lastOneWithoutThreeList = new(targetInt);
-        List<ulong> lastOneWithoutThreePow2List = new(targetInt);
-        List<uint> lastSevenWithoutThreeList = new(targetInt);
-        List<ulong> lastSevenWithoutThreePow2List = new(targetInt);
-        List<uint> lastNineWithoutThreeList = new(targetInt);
-        List<ulong> lastNineWithoutThreePow2List = new(targetInt);
-
-        uint candidate = 2U;
-        int allCount = 0;
-        int lastOneCount = 0;
-        int lastSevenCount = 0;
-        int lastThreeCount = 0;
-        int lastNineCount = 0;
-
-        while (allCount < targetInt ||
-            lastOneCount < targetInt ||
-            lastSevenCount < targetInt ||
-            lastThreeCount < targetInt ||
-            lastNineCount < targetInt)
+        if (((decimalMask >> remainder10) & 1) == 0)
         {
-            bool isPrime = true;
-            int primesCount = primes.Count;
-            for (int i = 0; i < primesCount; i++)
-            {
-                uint p = primes[i];
-                if (p * p > candidate)
-                {
-                    break;
-                }
-
-                if (candidate % p == 0U)
-                {
-                    isPrime = false;
-                    break;
-                }
-            }
-
-            if (isPrime)
-            {
-                primes.Add(candidate);
-                ulong candidateSquared = checked((ulong)candidate * candidate);
-                if (allCount < targetInt)
-                {
-                    all[allCount] = candidate;
-                    allPow2[allCount] = candidateSquared;
-                    allCount++;
-                }
-
-                if (candidate != 2U)
-                {
-                    LastDigit lastDigit = GetLastDigit(candidate);
-                    bool allowedForLastOne = IsAllowedForLastOne(candidate, lastDigit);
-                    bool allowedForLastSeven = IsAllowedForLastSeven(candidate, lastDigit);
-                    bool allowedForLastThree = IsAllowedForLastThree(candidate, lastDigit);
-                    bool allowedForLastNine = IsAllowedForLastNine(candidate, lastDigit);
-                    bool lastDigitIsThree = lastDigit == LastDigit.Three;
-
-                    if (allowedForLastOne && lastOneCount < targetInt)
-                    {
-                        lastOne[lastOneCount] = candidate;
-                        lastOnePow2[lastOneCount] = candidateSquared;
-                        lastOneCount++;
-                    }
-
-                    if (allowedForLastSeven && lastSevenCount < targetInt)
-                    {
-                        lastSeven[lastSevenCount] = candidate;
-                        lastSevenPow2[lastSevenCount] = candidateSquared;
-                        lastSevenCount++;
-                    }
-
-                    if (allowedForLastThree && lastThreeCount < targetInt)
-                    {
-                        lastThree[lastThreeCount] = candidate;
-                        lastThreePow2[lastThreeCount] = candidateSquared;
-                        lastThreeCount++;
-                    }
-
-                    if (allowedForLastNine && lastNineCount < targetInt)
-                    {
-                        lastNine[lastNineCount] = candidate;
-                        lastNinePow2[lastNineCount] = candidateSquared;
-                        lastNineCount++;
-                    }
-
-                    if (!lastDigitIsThree && allowedForLastOne)
-                    {
-                        lastOneWithoutThreeList.Add(candidate);
-                        lastOneWithoutThreePow2List.Add(candidateSquared);
-                    }
-
-                    if (!lastDigitIsThree && allowedForLastSeven)
-                    {
-                        lastSevenWithoutThreeList.Add(candidate);
-                        lastSevenWithoutThreePow2List.Add(candidateSquared);
-                    }
-
-                    if (!lastDigitIsThree && allowedForLastNine)
-                    {
-                        lastNineWithoutThreeList.Add(candidate);
-                        lastNineWithoutThreePow2List.Add(candidateSquared);
-                    }
-                }
-            }
-
-            candidate = candidate == 2U ? 3U : candidate + 2U;
+            return false;
         }
 
-        lastOneWithoutThree = lastOneWithoutThreeList.ToArray();
-        lastOneWithoutThreePow2 = lastOneWithoutThreePow2List.ToArray();
-        lastSevenWithoutThree = lastSevenWithoutThreeList.ToArray();
-        lastSevenWithoutThreePow2 = lastSevenWithoutThreePow2List.ToArray();
-        lastNineWithoutThree = lastNineWithoutThreeList.ToArray();
-        lastNineWithoutThreePow2 = lastNineWithoutThreePow2List.ToArray();
-    }
-
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static LastDigit GetLastDigit(uint prime)
-    {
-        return (prime % 10U) switch
+        if (remainder8 != 1 && remainder8 != 7)
         {
-            1U => LastDigit.One,
-            3U => LastDigit.Three,
-            5U => LastDigit.Five,
-            7U => LastDigit.Seven,
-            9U => LastDigit.Nine,
-            _ => throw new ArgumentOutOfRangeException(nameof(prime)),
-        };
-    }
+            return false;
+        }
 
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static bool IsAllowedForLastOne(uint prime, LastDigit lastDigit)
-    {
-        // TODO: Swap the `% 10` usage for ULongExtensions.Mod10 so the hot classification path
-        // reuses the benchmarked residue helper instead of repeated divisions.
-        return lastDigit switch
+        if (remainder3 == 0 || remainder5 == 0 || remainder7 == 0 || remainder11 == 0)
         {
-            LastDigit.One or LastDigit.Three or LastDigit.Nine => true,
-            LastDigit.Seven => prime == 7U,
-            _ => prime == 11U,
-        };
-    }
+            return false;
+        }
 
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static bool IsAllowedForLastSeven(uint prime, LastDigit lastDigit)
-    {
-        // TODO: Route this `% 10` classification through ULongExtensions.Mod10 to match the faster
-        // residue helper used elsewhere in the scanner.
-        return lastDigit switch
-        {
-            LastDigit.Three or LastDigit.Seven or LastDigit.Nine => true,
-            _ => prime == 11U,
-        };
-    }
-
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static bool IsAllowedForLastThree(uint prime, LastDigit lastDigit)
-    {
-        // TODO: Replace the `% 10` residue classification with ULongExtensions.Mod10 once the helper
-        // migrates to UInt32 so we can reuse the optimized decimal residue path everywhere.
-        return lastDigit switch
-        {
-            LastDigit.Three or LastDigit.Seven => true,
-            LastDigit.One => prime == 11U,
-            LastDigit.Nine => prime == 19U,
-            _ => false,
-        };
-    }
-
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static bool IsAllowedForLastNine(uint prime, LastDigit lastDigit)
-    {
-        // TODO: Replace the `% 10` residue classification with ULongExtensions.Mod10 when the helper
-        // supports UInt32 inputs so the residue tables share the optimized decimal path.
-        return lastDigit switch
-        {
-            LastDigit.Three or LastDigit.Seven or LastDigit.Nine => true,
-            LastDigit.One => prime == 11U,
-            _ => false,
-        };
+        return true;
     }
 }

PerfectNumbers.Core/ExponentRemainderStepperCpu.cs

@@ -74,7 +74,7 @@ internal struct ExponentRemainderStepperCpu
         // single-block divisor-cycle snapshot so we can skip the powmod entirely and reuse the
         // cached Montgomery residue ladder highlighted in MersenneDivisorCycleLengthGpuBenchmarks.
         ulong multiplier = delta.Pow2MontgomeryModWindowedCpu(_divisor, keepMontgomery: true);
-        _currentMontgomery = _currentMontgomery.MontgomeryMultiplyCpu(multiplier, _modulus, _nPrime);
+        _currentMontgomery = _currentMontgomery.MontgomeryMultiply(multiplier, _modulus, _nPrime);
         PreviousExponent = exponent;
         return ReduceCurrent();
     }
@@ -92,7 +92,7 @@ internal struct ExponentRemainderStepperCpu
         // TODO: Reuse the divisor-cycle derived Montgomery delta once the cache exposes single-cycle
         // lookups so this branch also avoids recomputing powmods when the snapshot lacks the divisor.
         ulong multiplier = delta.Pow2MontgomeryModWindowedCpu(_divisor, keepMontgomery: true);
-        _currentMontgomery = _currentMontgomery.MontgomeryMultiplyCpu(multiplier, _modulus, _nPrime);
+        _currentMontgomery = _currentMontgomery.MontgomeryMultiply(multiplier, _modulus, _nPrime);
         PreviousExponent = exponent;
         return _currentMontgomery == _montgomeryOne;
     }
@@ -126,7 +126,7 @@ internal struct ExponentRemainderStepperCpu
         // TODO: Once the divisor-cycle cache exposes a direct Montgomery delta, multiply it here instead
         // of relying on the caller-provided delta so incremental scans remain in sync with the snapshot
         // without computing additional cycles or mutating cache state.
-        _currentMontgomery = _currentMontgomery.MontgomeryMultiplyCpu(montgomeryDelta, _modulus, _nPrime);
+        _currentMontgomery = _currentMontgomery.MontgomeryMultiply(montgomeryDelta, _modulus, _nPrime);
         PreviousExponent = exponent;
         isUnity = _currentMontgomery == _montgomeryOne;
         return true;
@@ -138,5 +138,5 @@ internal struct ExponentRemainderStepperCpu
         PreviousExponent = exponent;
     }
 
-    private ulong ReduceCurrent() => _currentMontgomery.MontgomeryMultiplyCpu(1UL, _modulus, _nPrime);
+    private ulong ReduceCurrent() => _currentMontgomery.MontgomeryMultiply(1UL, _modulus, _nPrime);
 }

PerfectNumbers.Core/Gpu/AcceleratorPool.cs

@@ -1,61 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu
-{
-	public struct AcceleratorPool
-	{
-		internal readonly Context Context;
-		internal readonly Device Device;
-		internal readonly Accelerator[] Accelerators;
-
-		private int _index;
-
-		public int Rent()
-		{
-			Atomic.CompareExchange(ref _index, Capacity, 0);
-			var index = Atomic.Add(ref _index, 1);
-			if (index >= Capacity)
-			{
-				index -= Capacity;
-			}
-
-			return index;
-		}
-
-		public void Return(int acceleratorIndex)
-		{
-			// Intentionally left empty - there's nothing to do here. We're not really renting anything.
-		}
-
-		public static readonly AcceleratorPool Shared = new(PerfectNumberConstants.RollingAccelerators);
-
-		private readonly int Capacity;
-
-		public AcceleratorPool(int capacity)
-		{
-			Console.WriteLine("Creating accelerators");
-			Capacity = capacity;
-			var context = Context.CreateDefault();
-			var device = context.GetPreferredDevice(false);
-			Context = context;
-			Device = device;
-			int acceleratorsInContext = 0;
-			int acceleratorIndex = 0;
-			Accelerators = [.. Enumerable.Range(0, capacity).Select(_ =>
-			{
-				Console.WriteLine($"Preparing accelerator {acceleratorIndex++}");
-				Accelerator accelerator = device.CreateAccelerator(context);
-				acceleratorsInContext++;
-				if (acceleratorsInContext >= 128)
-				{
-					context = Context.CreateDefault();
-					device = context.GetPreferredDevice(false);
-					acceleratorsInContext = 0;
-				}
-
-				return accelerator;
-			})];
-		}
-	}
-}

PerfectNumbers.Core/Gpu/AcceleratorReferenceComparer.cs

@@ -1,13 +0,0 @@
-using System.Runtime.CompilerServices;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu;
-
-internal sealed class AcceleratorReferenceComparer : IEqualityComparer<Accelerator>
-{
-	internal static AcceleratorReferenceComparer Instance { get; } = new();
-
-	public bool Equals(Accelerator? x, Accelerator? y) => ReferenceEquals(x, y);
-
-	public int GetHashCode(Accelerator obj) => RuntimeHelpers.GetHashCode(obj);
-}

PerfectNumbers.Core/Gpu/Accelerators/AcceleratorExtensions.cs

@@ -1,34 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-public static class AcceleratorExtensions
-{
-	public static MemoryBuffer1D<ulong, Stride1D.Dense> CopySpanToDevice(this Accelerator accelerator, AcceleratorStream stream, in ulong[] span)
-	{
-		MemoryBuffer1D<ulong, Stride1D.Dense>? buffer;
-		buffer = accelerator.Allocate1D(stream, span);
-
-		return buffer;
-	}
-
-	public static MemoryBuffer1D<ulong, Stride1D.Dense> CopyUintSpanToDevice(this Accelerator accelerator, AcceleratorStream stream, ReadOnlySpan<uint> span)
-	{
-		MemoryBuffer1D<ulong, Stride1D.Dense>? buffer;
-		buffer = accelerator.Allocate1D<ulong>(span.Length);
-
-		if (!span.IsEmpty)
-		{
-			var converted = new ulong[span.Length];
-			for (int i = 0; i < span.Length; i++)
-			{
-				converted[i] = span[i];
-			}
-
-			buffer.View.CopyFromCPU(stream, converted);
-		}
-
-		return buffer;
-	}
-}

PerfectNumbers.Core/Gpu/Accelerators/AcceleratorStreamPool.cs

@@ -1,42 +0,0 @@
-using System.Collections.Concurrent;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-public static class AcceleratorStreamPool
-{
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-	private static readonly SemaphoreSlim[] _locks = new SemaphoreSlim[PerfectNumberConstants.RollingAccelerators];
-	private static readonly ConcurrentQueue<AcceleratorStream>[] _streams = new ConcurrentQueue<AcceleratorStream> [PerfectNumberConstants.RollingAccelerators];
-
-	private static SemaphoreSlim CreateLock() => new(PerfectNumberConstants.ThreadsByAccelerator);
-
-
-	// private static int _rented;
-
-	public static AcceleratorStream Rent(int acceleratorIndex)
-	{
-		var streamLock = _locks[acceleratorIndex];
-		var queue = _streams[acceleratorIndex];
-
-		streamLock.Wait();
-
-		return queue.TryDequeue(out var stream)
-			? stream
-			: _accelerators[acceleratorIndex].CreateStream();
-	}
-
-	public static void Return(int acceleratorIndex, AcceleratorStream stream)
-	{
-		var streamLock = _locks[acceleratorIndex];
-		var queue = _streams[acceleratorIndex];
-		queue.Enqueue(stream);
-		streamLock.Release();
-	}
-
-	public static void WarmUp(int acceleratorIndex)
-	{
-		_streams[acceleratorIndex] = new();
-		_locks[acceleratorIndex] = CreateLock();
-	}
-}

PerfectNumbers.Core/Gpu/Accelerators/HeuristicCombinedGpuTables.cs

@@ -1,69 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-internal readonly struct HeuristicCombinedGpuTables
-{
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
-	private static readonly HeuristicCombinedGpuTables[] _sharedTables = new HeuristicCombinedGpuTables[PerfectNumberConstants.RollingAccelerators];
-
-	internal static void WarmUp(int acceleratorIndex, AcceleratorStream stream) => _sharedTables[acceleratorIndex] = new(_accelerators[acceleratorIndex], stream);
-
-	internal static HeuristicCombinedGpuTables GetStaticTables(int acceleratorIndex) => _sharedTables[acceleratorIndex];
-
-	internal HeuristicCombinedGpuTables(Accelerator accelerator, AcceleratorStream stream)
-	{
-		var combinedEnding1 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding1;
-		HeuristicCombinedDivisorsEnding1 = accelerator.CopySpanToDevice(stream, combinedEnding1);
-		var combinedSquaresEnding1 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding1Squares;
-		HeuristicCombinedDivisorSquaresEnding1 = accelerator.CopySpanToDevice(stream, combinedSquaresEnding1);
-
-		var combinedEnding3 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding3;
-		HeuristicCombinedDivisorsEnding3 = accelerator.CopySpanToDevice(stream, combinedEnding3);
-		var combinedSquaresEnding3 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding3Squares;
-		HeuristicCombinedDivisorSquaresEnding3 = accelerator.CopySpanToDevice(stream, combinedSquaresEnding3);
-
-		var combinedEnding7 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding7;
-		HeuristicCombinedDivisorsEnding7 = accelerator.CopySpanToDevice(stream, combinedEnding7);
-		var combinedSquaresEnding7 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding7Squares;
-		HeuristicCombinedDivisorSquaresEnding7 = accelerator.CopySpanToDevice(stream, combinedSquaresEnding7);
-
-		var combinedEnding9 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding9;
-		HeuristicCombinedDivisorsEnding9 = accelerator.CopySpanToDevice(stream, combinedEnding9);
-		var combinedSquaresEnding9 = HeuristicCombinedPrimeTester.CombinedDivisorsEnding9Squares;
-		HeuristicCombinedDivisorSquaresEnding9 = accelerator.CopySpanToDevice(stream, combinedSquaresEnding9);
-	}
-
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorsEnding1;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorSquaresEnding1;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorsEnding3;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorSquaresEnding3;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorsEnding7;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorSquaresEnding7;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorsEnding9;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicCombinedDivisorSquaresEnding9;
-
-	internal HeuristicCombinedGpuViews CreateViews() => new(
-			HeuristicCombinedDivisorsEnding1.View,
-			HeuristicCombinedDivisorsEnding3.View,
-			HeuristicCombinedDivisorsEnding7.View,
-			HeuristicCombinedDivisorsEnding9.View,
-			HeuristicCombinedDivisorSquaresEnding1.View,
-			HeuristicCombinedDivisorSquaresEnding3.View,
-			HeuristicCombinedDivisorSquaresEnding7.View,
-			HeuristicCombinedDivisorSquaresEnding9.View);
-
-	internal void Dispose()
-	{
-		HeuristicCombinedDivisorsEnding1.Dispose();
-		HeuristicCombinedDivisorSquaresEnding1.Dispose();
-		HeuristicCombinedDivisorsEnding3.Dispose();
-		HeuristicCombinedDivisorSquaresEnding3.Dispose();
-		HeuristicCombinedDivisorsEnding7.Dispose();
-		HeuristicCombinedDivisorSquaresEnding7.Dispose();
-		HeuristicCombinedDivisorsEnding9.Dispose();
-		HeuristicCombinedDivisorSquaresEnding9.Dispose();
-	}
-}

PerfectNumbers.Core/Gpu/Accelerators/HeuristicCombinedGpuViews.cs

@@ -1,45 +0,0 @@
-using System.Runtime.CompilerServices;
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-public readonly struct HeuristicCombinedGpuViews(
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding1,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding3,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding7,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding9,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorSquaresEnding1,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorSquaresEnding3,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorSquaresEnding7,
-		ArrayView1D<ulong, Stride1D.Dense> combinedDivisorSquaresEnding9)
-{
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding1 = combinedDivisorsEnding1;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding3 = combinedDivisorsEnding3;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding7 = combinedDivisorsEnding7;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding9 = combinedDivisorsEnding9;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding1 = combinedDivisorSquaresEnding1;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding3 = combinedDivisorSquaresEnding3;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding7 = combinedDivisorSquaresEnding7;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding9 = combinedDivisorSquaresEnding9;
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ArrayView1D<ulong, Stride1D.Dense> SelectDivisors(byte ending) => ending switch
-	{
-		1 => CombinedDivisorsEnding1,
-		3 => CombinedDivisorsEnding3,
-		7 => CombinedDivisorsEnding7,
-		9 => CombinedDivisorsEnding9,
-		_ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-	};
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ArrayView1D<ulong, Stride1D.Dense> SelectDivisorSquares(byte ending) => ending switch
-	{
-		1 => CombinedDivisorSquaresEnding1,
-		3 => CombinedDivisorSquaresEnding3,
-		7 => CombinedDivisorSquaresEnding7,
-		9 => CombinedDivisorSquaresEnding9,
-		_ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-	};
-}

PerfectNumbers.Core/Gpu/Accelerators/HeuristicGroupABGpuTables.cs

@@ -1,79 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-internal sealed class HeuristicGroupABGpuTables
-{
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
-	private static readonly HeuristicGroupABGpuTables[] _sharedTables = new HeuristicGroupABGpuTables[PerfectNumberConstants.RollingAccelerators];
-
-	private static readonly SemaphoreSlim[] _locks = [..Enumerable.Range(1, PerfectNumberConstants.RollingAccelerators).Select(_ => new SemaphoreSlim(1))];
-
-	internal static HeuristicGroupABGpuTables EnsureStaticTables(int acceleratorIndex, AcceleratorStream stream)
-	{
-		var @lock = _locks[acceleratorIndex];
-		@lock.Wait();
-		if (_sharedTables[acceleratorIndex] is {} existing)
-		{
-			@lock.Release();
-			return existing;
-		}
-
-		var accelerator = _accelerators[acceleratorIndex];
-		existing = new(accelerator, stream);
-		_sharedTables[acceleratorIndex] = existing;
-		@lock.Release();
-		return existing;
-	}
-
-	internal HeuristicGroupABGpuTables(Accelerator accelerator, AcceleratorStream stream)
-	{
-		var heuristicGroupA = HeuristicPrimeSieves.GroupADivisorsStorage;
-		HeuristicGroupADivisors = accelerator.CopySpanToDevice(stream, heuristicGroupA);
-
-		var heuristicGroupASquares = HeuristicPrimeSieves.GroupADivisorSquaresStorage;
-		HeuristicGroupADivisorSquares = accelerator.CopySpanToDevice(stream, heuristicGroupASquares);
-
-		HeuristicGroupBDivisorsEnding1 = accelerator.CopyUintSpanToDevice(stream, DivisorGenerator.SmallPrimesLastOneWithoutLastThree);
-		HeuristicGroupBDivisorSquaresEnding1 = accelerator.CopySpanToDevice(stream, DivisorGenerator.SmallPrimesPow2LastOneWithoutLastThree);
-
-		HeuristicGroupBDivisorsEnding7 = accelerator.CopyUintSpanToDevice(stream, DivisorGenerator.SmallPrimesLastSevenWithoutLastThree);
-		HeuristicGroupBDivisorSquaresEnding7 = accelerator.CopySpanToDevice(stream, DivisorGenerator.SmallPrimesPow2LastSevenWithoutLastThree);
-
-		HeuristicGroupBDivisorsEnding9 = accelerator.CopyUintSpanToDevice(stream, DivisorGenerator.SmallPrimesLastNineWithoutLastThree);
-		HeuristicGroupBDivisorSquaresEnding9 = accelerator.CopySpanToDevice(stream, DivisorGenerator.SmallPrimesPow2LastNineWithoutLastThree);
-	}
-
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupADivisors;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupADivisorSquares;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorsEnding1;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorSquaresEnding1;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorsEnding7;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorSquaresEnding7;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorsEnding9;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorSquaresEnding9;
-
-	internal HeuristicGroupABGpuViews CreateViews() => new(
-			HeuristicGroupADivisors.View,
-			HeuristicGroupADivisorSquares.View,
-			HeuristicGroupBDivisorsEnding1.View,
-			HeuristicGroupBDivisorSquaresEnding1.View,
-			HeuristicGroupBDivisorsEnding7.View,
-			HeuristicGroupBDivisorSquaresEnding7.View,
-			HeuristicGroupBDivisorsEnding9.View,
-			HeuristicGroupBDivisorSquaresEnding9.View);
-
-	internal void Dispose()
-	{
-		HeuristicGroupADivisors.Dispose();
-		HeuristicGroupADivisorSquares.Dispose();
-		HeuristicGroupBDivisorsEnding1.Dispose();
-		HeuristicGroupBDivisorSquaresEnding1.Dispose();
-		HeuristicGroupBDivisorsEnding7.Dispose();
-		HeuristicGroupBDivisorSquaresEnding7.Dispose();
-		HeuristicGroupBDivisorsEnding9.Dispose();
-		HeuristicGroupBDivisorSquaresEnding9.Dispose();
-	}
-}

PerfectNumbers.Core/Gpu/Accelerators/HeuristicGroupABGpuViews.cs

@@ -1,63 +0,0 @@
-using System.Runtime.CompilerServices;
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-public readonly struct HeuristicGroupABGpuViews(
-		ArrayView1D<ulong, Stride1D.Dense> groupADivisors,
-		ArrayView1D<ulong, Stride1D.Dense> groupADivisorSquares,
-		ArrayView1D<ulong, Stride1D.Dense> groupBDivisorsEnding1,
-		ArrayView1D<ulong, Stride1D.Dense> groupBDivisorSquaresEnding1,
-		ArrayView1D<ulong, Stride1D.Dense> groupBDivisorsEnding7,
-		ArrayView1D<ulong, Stride1D.Dense> groupBDivisorSquaresEnding7,
-		ArrayView1D<ulong, Stride1D.Dense> groupBDivisorsEnding9,
-		ArrayView1D<ulong, Stride1D.Dense> groupBDivisorSquaresEnding9)
-{
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupADivisors = groupADivisors;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupADivisorSquares = groupADivisorSquares;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorsEnding1 = groupBDivisorsEnding1;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorSquaresEnding1 = groupBDivisorSquaresEnding1;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorsEnding7 = groupBDivisorsEnding7;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorSquaresEnding7 = groupBDivisorSquaresEnding7;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorsEnding9 = groupBDivisorsEnding9;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorSquaresEnding9 = groupBDivisorSquaresEnding9;
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ArrayView1D<ulong, Stride1D.Dense> SelectGroupB(byte ending) => ending switch
-	{
-		1 => GroupBDivisorsEnding1,
-		7 => GroupBDivisorsEnding7,
-		9 => GroupBDivisorsEnding9,
-		_ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-	};
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ArrayView1D<ulong, Stride1D.Dense> SelectGroupBSquares(byte ending) => ending switch
-	{
-		1 => GroupBDivisorSquaresEnding1,
-		7 => GroupBDivisorSquaresEnding7,
-		9 => GroupBDivisorSquaresEnding9,
-		_ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-	};
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ArrayView1D<ulong, Stride1D.Dense> SelectDivisors(HeuristicGpuDivisorTableKind kind) => kind switch
-	{
-		HeuristicGpuDivisorTableKind.GroupA => GroupADivisors,
-		HeuristicGpuDivisorTableKind.GroupBEnding1 => GroupBDivisorsEnding1,
-		HeuristicGpuDivisorTableKind.GroupBEnding7 => GroupBDivisorsEnding7,
-		HeuristicGpuDivisorTableKind.GroupBEnding9 => GroupBDivisorsEnding9,
-		_ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-	};
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public ArrayView1D<ulong, Stride1D.Dense> SelectDivisorSquares(HeuristicGpuDivisorTableKind kind) => kind switch
-	{
-		HeuristicGpuDivisorTableKind.GroupA => GroupADivisorSquares,
-		HeuristicGpuDivisorTableKind.GroupBEnding1 => GroupBDivisorSquaresEnding1,
-		HeuristicGpuDivisorTableKind.GroupBEnding7 => GroupBDivisorSquaresEnding7,
-		HeuristicGpuDivisorTableKind.GroupBEnding9 => GroupBDivisorSquaresEnding9,
-		_ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-	};
-}

PerfectNumbers.Core/Gpu/Accelerators/HeuristicGroupABPrimeTesterAccelerator.cs

@@ -1,174 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-internal sealed class HeuristicGroupABPrimeTesterAccelerator
-{
-	#region Pool
-
-	[ThreadStatic]
-	private static Queue<HeuristicGroupABPrimeTesterAccelerator>? Pool;
-
-	internal static void WarmUp()
-	{
-		Accelerator[]? accelerators = AcceleratorPool.Shared.Accelerators;
-		int acceleratorCount = accelerators.Length;
-		for (var i = 0; i < acceleratorCount; i++)
-		{
-			Console.WriteLine($"Preparing heuristic accelerator {i}...");
-			var accelerator = accelerators[i];
-			AcceleratorStream stream = accelerator.CreateStream();
-			_ = HeuristicGroupABGpuTables.EnsureStaticTables(i, stream);
-			// _ = GpuKernelPool.GetOrAddKernels(accelerator, stream, KernelType.None);
-			// KernelContainer kernels = GpuKernelPool.GetOrAddKernels(accelerator, stream);
-			// GpuStaticTableInitializer.EnsureStaticTables(accelerator, kernels, stream);
-			stream.Synchronize();
-			stream.Dispose();
-			Console.WriteLine($"Heuristic accelerator {i} is ready");
-		}
-	}
-
-	internal static HeuristicGroupABPrimeTesterAccelerator Rent(int minBufferCapacity = 1)
-	{
-		var pool = Pool ??= new();
-		if (!pool.TryDequeue(out var lease))
-		{
-			lease = new HeuristicGroupABPrimeTesterAccelerator(minBufferCapacity);
-		}
-		else
-		{
-			lease.EnsureCapacity(minBufferCapacity);
-		}
-
-		return lease;
-	}
-
-	internal static void Return(HeuristicGroupABPrimeTesterAccelerator lease)
-	{
-		var pool = Pool ??= new();
-		pool.Enqueue(lease);
-	}
-
-	internal static void DisposeAll()
-	{
-		if (Pool != null)
-		{
-			while (Pool.TryDequeue(out var lease))
-			{
-				lease.DisposeResources();
-			}
-		}
-	}
-
-	internal static void Clear()
-	{
-		if (Pool != null)
-		{
-			var retained = new List<HeuristicGroupABPrimeTesterAccelerator>();
-			while (Pool.TryDequeue(out var lease))
-			{
-				lease.DisposeResources();
-			}
-		}
-	}
-
-	#endregion
-
-	public readonly HeuristicGroupABGpuViews DivisorTables;
-	internal readonly Context Context;
-	public readonly Accelerator Accelerator;
-
-	[ThreadStatic]
-	public static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>>>? SmallPrimeSieveKernel;
-
-	internal static Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>> GetSmallPrimeSieveKernel(Accelerator accelerator)
-	{
-		var pool = SmallPrimeSieveKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
-
-		cached = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>>(PrimeTesterKernels.SmallPrimeSieveKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
-
-	public readonly Kernel HeuristicTrialDivisionKernel;
-
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? Input = null;
-	public MemoryBuffer1D<byte, Stride1D.Dense>? Output = null;
-	public MemoryBuffer1D<int, Stride1D.Dense>? HeuristicFlag = null!;
-	public int BufferCapacity;
-
-	private HeuristicGroupABGpuTables _sharedTables;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupADivisors => _sharedTables.HeuristicGroupADivisors;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupADivisorSquares => _sharedTables.HeuristicGroupADivisorSquares;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorsEnding1 => _sharedTables.HeuristicGroupBDivisorsEnding1;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorSquaresEnding1 => _sharedTables.HeuristicGroupBDivisorSquaresEnding1;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorsEnding7 => _sharedTables.HeuristicGroupBDivisorsEnding7;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorSquaresEnding7 => _sharedTables.HeuristicGroupBDivisorSquaresEnding7;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorsEnding9 => _sharedTables.HeuristicGroupBDivisorsEnding9;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> HeuristicGroupBDivisorSquaresEnding9 => _sharedTables.HeuristicGroupBDivisorSquaresEnding9;
-
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-	internal readonly int AcceleratorIndex;
-
-	internal HeuristicGroupABPrimeTesterAccelerator(int minBufferCapacity)
-	{
-		var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		AcceleratorIndex = acceleratorIndex;
-		Accelerator accelerator = _accelerators[acceleratorIndex];
-		Context = accelerator.Context;
-
-		Accelerator = accelerator;
-		EnsureCapacity(minBufferCapacity);
-
-		HeuristicTrialDivisionKernel = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<int>, ulong, ulong, HeuristicGpuDivisorTableKind, HeuristicGroupABGpuViews>(PrimeTesterKernels.HeuristicTrialGroupABDivisionKernel));
-
-		AcceleratorStream stream = AcceleratorStreamPool.Rent(acceleratorIndex);
-		
-		// GpuStaticTableInitializer.EnsureStaticTables(accelerator, kernels, stream);
-
-		_sharedTables = HeuristicGroupABGpuTables.EnsureStaticTables(acceleratorIndex, stream);
-		DivisorTables = _sharedTables.CreateViews();
-
-		stream.Synchronize();
-		AcceleratorStreamPool.Return(acceleratorIndex, stream); 
-	}
-
-	public void EnsureCapacity(int minCapacity)
-	{
-		if (minCapacity <= BufferCapacity)
-		{
-			return;
-		}
-
-		Input?.Dispose();
-		Output?.Dispose();
-		HeuristicFlag?.Dispose();
-
-		Input = Accelerator.Allocate1D<ulong>(minCapacity);
-		Output = Accelerator.Allocate1D<byte>(minCapacity);
-		HeuristicFlag = Accelerator.Allocate1D<int>(minCapacity);
-
-		BufferCapacity = minCapacity;
-	}
-
-	public void Dispose()
-	{
-		Return(this);
-	}
-
-	internal void DisposeResources()
-	{
-		Input?.Dispose();
-		Output?.Dispose();
-		HeuristicFlag?.Dispose();
-		// ReleaseSharedTables(_sharedTables);
-		// These resources are shared between GPU leases
-		// Accelerator.Dispose();
-		// AcceleratorContext.Dispose();
-	}
-}

PerfectNumbers.Core/Gpu/Accelerators/LastDigitGpuTables.cs

@@ -1,58 +0,0 @@
-using System.Runtime.CompilerServices;
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-internal readonly struct LastDigitGpuTables
-{
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-	private static readonly LastDigitGpuTables[] _sharedTables = new LastDigitGpuTables[PerfectNumberConstants.RollingAccelerators];
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	internal static LastDigitGpuTables GetStaticTables(int acceleratorIndex) => _sharedTables[acceleratorIndex];
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	internal static void WarmUp(int acceleratorIndex, AcceleratorStream stream) => _sharedTables[acceleratorIndex] = new LastDigitGpuTables(_accelerators[acceleratorIndex], stream);
-
-	internal LastDigitGpuTables(Accelerator accelerator, AcceleratorStream stream)
-	{
-		var primesLastOne = DivisorGenerator.SmallPrimesLastOne;
-		var primesLastSeven = DivisorGenerator.SmallPrimesLastSeven;
-		var primesLastThree = DivisorGenerator.SmallPrimesLastThree;
-		var primesLastNine = DivisorGenerator.SmallPrimesLastNine;
-		var primesPow2LastOne = DivisorGenerator.SmallPrimesPow2LastOne;
-		var primesPow2LastSeven = DivisorGenerator.SmallPrimesPow2LastSeven;
-		var primesPow2LastThree = DivisorGenerator.SmallPrimesPow2LastThree;
-		var primesPow2LastNine = DivisorGenerator.SmallPrimesPow2LastNine;
-		DevicePrimesLastOne = accelerator.Allocate1D(stream, primesLastOne);
-		DevicePrimesLastSeven = accelerator.Allocate1D(stream, primesLastSeven);
-		DevicePrimesLastThree = accelerator.Allocate1D(stream, primesLastThree);
-		DevicePrimesLastNine = accelerator.Allocate1D(stream, primesLastNine);
-		DevicePrimesPow2LastOne = accelerator.Allocate1D(stream, primesPow2LastOne);
-		DevicePrimesPow2LastSeven = accelerator.Allocate1D(stream, primesPow2LastSeven);
-		DevicePrimesPow2LastThree = accelerator.Allocate1D(stream, primesPow2LastThree);
-		DevicePrimesPow2LastNine = accelerator.Allocate1D(stream, primesPow2LastNine);
-	}
-
-	internal readonly MemoryBuffer1D<uint, Stride1D.Dense> DevicePrimesLastOne;
-	internal readonly MemoryBuffer1D<uint, Stride1D.Dense> DevicePrimesLastSeven;
-	internal readonly MemoryBuffer1D<uint, Stride1D.Dense> DevicePrimesLastThree;
-	internal readonly MemoryBuffer1D<uint, Stride1D.Dense> DevicePrimesLastNine;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> DevicePrimesPow2LastOne;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> DevicePrimesPow2LastSeven;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> DevicePrimesPow2LastThree;
-	internal readonly MemoryBuffer1D<ulong, Stride1D.Dense> DevicePrimesPow2LastNine;
-
-	internal void Dispose()
-	{
-		DevicePrimesLastOne.Dispose();
-		DevicePrimesLastSeven.Dispose();
-		DevicePrimesLastThree.Dispose();
-		DevicePrimesLastNine.Dispose();
-		DevicePrimesPow2LastOne.Dispose();
-		DevicePrimesPow2LastSeven.Dispose();
-		DevicePrimesPow2LastThree.Dispose();
-		DevicePrimesPow2LastNine.Dispose();
-	}
-}

PerfectNumbers.Core/Gpu/Accelerators/PrimeOrderCalculatorAccelerator.cs

@@ -1,300 +0,0 @@
-using System.Runtime.CompilerServices;
-using ILGPU;
-using ILGPU.Runtime;
-using PerfectNumbers.Core.Gpu.Kernels;
-
-namespace PerfectNumbers.Core.Gpu.Accelerators;
-
-public sealed class PrimeOrderCalculatorAccelerator
-{
-	#region Pool
-
-	[ThreadStatic]
-	private static Queue<PrimeOrderCalculatorAccelerator>? _pool;
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public static PrimeOrderCalculatorAccelerator Rent(int primeTesterCapacity)
-	{
-		var pool = _pool ??= [];
-		if (!pool.TryDequeue(out var gpu))
-		{
-			int acceleratorIndex = AcceleratorPool.Shared.Rent();
-			gpu = new(acceleratorIndex, PerfectNumberConstants.DefaultFactorsBuffer, primeTesterCapacity, PerfectNumberConstants.DefaultSmallPrimeFactorSlotCount, PerfectNumberConstants.DefaultSpecialMaxFactorCapacity);
-		}
-		else
-		{
-			gpu.EnsureCapacity(PerfectNumberConstants.DefaultFactorsBuffer, primeTesterCapacity);
-		}
-
-		return gpu;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public static void Return(PrimeOrderCalculatorAccelerator gpu) => _pool!.Enqueue(gpu);
-
-	internal static void Clear()
-	{
-		Queue<PrimeOrderCalculatorAccelerator>? pool = _pool;
-		if (pool != null)
-		{
-			while (pool.TryDequeue(out var gpu))
-			{
-				gpu.Dispose();
-			}
-		}
-	}
-
-	internal static void DisposeAll()
-	{
-		Queue<PrimeOrderCalculatorAccelerator>? pool = _pool;
-		if (pool != null)
-		{
-			while (pool.TryDequeue(out var gpu))
-			{
-				gpu.Dispose();
-			}
-		}
-	}
-
-	internal static void WarmUp()
-	{
-		Accelerator[] accelerators = AcceleratorPool.Shared.Accelerators;
-		int acceleratorCount = accelerators.Length;
-		for (var i = 0; i < acceleratorCount; i++)
-		{
-			Console.WriteLine($"Preparing accelerator {i}...");
-			var accelerator = accelerators[i];
-			AcceleratorStreamPool.WarmUp(i);
-			// Don't take this from the pool as quick uploads of data to the accelerator consumes much of GPU's memory and throws.
-			AcceleratorStream stream = accelerator.CreateStream();
-			// TODO: Review which tables are needed when final execution path is defined.
-			LastDigitGpuTables.WarmUp(i, stream);
-			HeuristicCombinedGpuTables.WarmUp(i, stream);
-			// SmallPrimeFactorGpuTables.WarmUp(i, stream);
-			// SharedHeuristicGpuTables.EnsureStaticTables(accelerator, stream);
-			// _ = GpuKernelPool.GetOrAddKernels(accelerator, stream, KernelType.None);
-			// KernelContainer kernels = GpuKernelPool.GetOrAddKernels(accelerator, stream);
-			// GpuStaticTableInitializer.EnsureStaticTables(accelerator, kernels, stream);
-			stream.Synchronize();
-			stream.Dispose();
-			accelerator.Synchronize();
-		}
-
-	}
-
-	#endregion
-	#region Static Tables
-
-	public readonly ArrayView1D<uint, Stride1D.Dense> DevicePrimesLastOne;
-	public readonly ArrayView1D<uint, Stride1D.Dense> DevicePrimesLastSeven;
-	public readonly ArrayView1D<uint, Stride1D.Dense> DevicePrimesLastThree;
-	public readonly ArrayView1D<uint, Stride1D.Dense> DevicePrimesLastNine;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> DevicePrimesPow2LastOne;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> DevicePrimesPow2LastSeven;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> DevicePrimesPow2LastThree;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> DevicePrimesPow2LastNine;
-
-	public readonly HeuristicCombinedGpuViews DivisorTables;
-
-	public readonly ArrayView1D<uint, Stride1D.Dense> SmallPrimeFactorPrimes;
-	public readonly ArrayView1D<ulong, Stride1D.Dense> SmallPrimeFactorSquares;
-
-	#endregion
-
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
-	public readonly Accelerator Accelerator;
-	public readonly int AcceleratorIndex;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> Input;
-	public MemoryBuffer1D<ulong, Stride1D.Dense> OutputUlong;
-	public MemoryBuffer1D<byte, Stride1D.Dense> OutputByte;
-	public MemoryBuffer1D<int, Stride1D.Dense> OutputInt;
-	public MemoryBuffer1D<KeyValuePair<ulong, int>, Stride1D.Dense> Pow2ModEntriesToTestOnDevice;
-	public readonly MemoryBuffer1D<int, Stride1D.Dense> SmallPrimeFactorCountSlot;
-	public readonly MemoryBuffer1D<ulong, Stride1D.Dense> SpecialMaxResult;
-
-	public Dictionary<ulong, int> Pow2ModEntriesToTestOnHost = [];
-
-	public readonly Action<AcceleratorStream, int, ulong, ArrayView1D<KeyValuePair<ulong, int>, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>> CheckFactorsKernelLauncher;
-
-	public readonly Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>> ConvertToStandardKernelLauncher;
-
-	public readonly Action<AcceleratorStream, Index1D, byte, ArrayView<int>, ulong, ulong, HeuristicCombinedGpuViews> HeuristicCombinedTrialDivisionKernelLauncher;
-	public readonly Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>> KeepMontgomeryKernelLauncher;
-	public readonly Action<AcceleratorStream, ulong, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> PollardRhoKernelLauncher;
-	public readonly Action<AcceleratorStream, Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>> Pow2ModWideKernelLauncher;
-	public readonly Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<byte>> SharesFactorKernelLauncher;
-	public readonly Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> SmallPrimeFactorKernelLauncher;
-	public readonly Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>> SmallPrimeSieveKernelLauncher;
-	public readonly Action<AcceleratorStream, Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> SpecialMaxKernelLauncher;
-
-	public void EnsureCapacity(int factorsCount, int primeTesterCapacity)
-	{
-		Accelerator accelerator = Accelerator;
-
-		MemoryBuffer1D<KeyValuePair<ulong, int>, Stride1D.Dense> pow2ModEntriesToTestOnDevice = Pow2ModEntriesToTestOnDevice;
-		if (pow2ModEntriesToTestOnDevice.Length < factorsCount)
-		{
-			lock (accelerator)
-			{
-				pow2ModEntriesToTestOnDevice.Dispose();
-				Pow2ModEntriesToTestOnDevice = accelerator.Allocate1D<KeyValuePair<ulong, int>>(factorsCount);
-			}
-		}
-
-		MemoryBuffer1D<ulong, Stride1D.Dense> input = Input;
-		if (input.Length < primeTesterCapacity)
-		{
-			lock (accelerator)
-			{
-				input.Dispose();
-				Input = accelerator.Allocate1D<ulong>(primeTesterCapacity);
-			}
-		}
-
-		MemoryBuffer1D<byte, Stride1D.Dense> outputByte = OutputByte;
-		if (outputByte.Length < primeTesterCapacity)
-		{
-			lock (accelerator)
-			{
-				outputByte.Dispose();
-				OutputByte = accelerator.Allocate1D<byte>(primeTesterCapacity);
-			}
-		}
-
-		MemoryBuffer1D<int, Stride1D.Dense> outputInt = OutputInt;
-		if (outputInt.Length < primeTesterCapacity)
-		{
-			lock (accelerator)
-			{
-				outputInt.Dispose();
-				OutputInt = accelerator.Allocate1D<int>(primeTesterCapacity);
-			}
-		}
-	}
-
-	public void EnsureSmallPrimeFactorSlotsCapacity(int newSize)
-	{
-		// Console.WriteLine($"Resizing GPU scratch buffer from pool ({buffer.SmallPrimeFactorPrimeSlots.Length} / {smallPrimeFactorSlotCount}), ({buffer.SpecialMaxFactors.Length}/{specialMaxFactorCapacity})");
-		var accelerator = Accelerator;
-		MemoryBuffer1D<ulong, Stride1D.Dense> outputUlong = OutputUlong;
-		if (outputUlong.Length < newSize)
-		{
-			lock (accelerator)
-			{
-				outputUlong.Dispose();
-				OutputUlong = accelerator.Allocate1D<ulong>(newSize);
-			}
-		}
-
-		MemoryBuffer1D<int, Stride1D.Dense> outputInt = OutputInt;
-		if (outputInt.Length < newSize)
-		{
-			lock (accelerator)
-			{
-				outputInt.Dispose();
-				OutputInt = accelerator.Allocate1D<int>(newSize);
-			}
-		}
-	}
-
-	public void EnsureSpecialMaxFactorsCapacity(int newSize)
-	{
-		var accelerator = Accelerator;
-		MemoryBuffer1D<ulong, Stride1D.Dense> input = Input;
-		if (input.Length < newSize)
-		{
-			lock (accelerator)
-			{
-				input.Dispose();
-				Input = accelerator.Allocate1D<ulong>(newSize);
-			}
-		}
-
-		MemoryBuffer1D<ulong, Stride1D.Dense> outputUlong = OutputUlong;
-		if (outputUlong.Length < newSize)
-		{
-			lock (accelerator)
-			{
-				outputUlong.Dispose();
-				OutputUlong = accelerator.Allocate1D<ulong>(newSize);
-			}
-		}
-	}
-
-	public PrimeOrderCalculatorAccelerator(int acceleratorIndex, int factorsCount, int primeTesterCapacity, int smallPrimeFactorSlotCount, int specialMaxFactorCapacity)
-	{
-		var accelerator = _accelerators[acceleratorIndex];
-		Accelerator = accelerator;
-		AcceleratorIndex = acceleratorIndex;
-		lock (accelerator)
-		{
-			Input = accelerator.Allocate1D<ulong>(Math.Max(specialMaxFactorCapacity, primeTesterCapacity));
-			OutputByte = Accelerator.Allocate1D<byte>(primeTesterCapacity);
-			OutputInt = Accelerator.Allocate1D<int>(Math.Max(primeTesterCapacity, smallPrimeFactorSlotCount));
-			OutputUlong = accelerator.Allocate1D<ulong>(Math.Max(specialMaxFactorCapacity, smallPrimeFactorSlotCount));
-			Pow2ModEntriesToTestOnDevice = accelerator.Allocate1D<KeyValuePair<ulong, int>>(factorsCount);
-			SmallPrimeFactorCountSlot = accelerator.Allocate1D<int>(1);
-			SpecialMaxResult = accelerator.Allocate1D<ulong>(1);
-
-			LastDigitGpuTables lastDigitSharedTables = LastDigitGpuTables.GetStaticTables(acceleratorIndex);
-			DevicePrimesLastOne = lastDigitSharedTables.DevicePrimesLastOne.View;
-			DevicePrimesLastSeven = lastDigitSharedTables.DevicePrimesLastSeven.View;
-			DevicePrimesLastThree = lastDigitSharedTables.DevicePrimesLastThree.View;
-			DevicePrimesLastNine = lastDigitSharedTables.DevicePrimesLastNine.View;
-			DevicePrimesPow2LastOne = lastDigitSharedTables.DevicePrimesPow2LastOne.View;
-			DevicePrimesPow2LastSeven = lastDigitSharedTables.DevicePrimesPow2LastSeven.View;
-			DevicePrimesPow2LastThree = lastDigitSharedTables.DevicePrimesPow2LastThree.View;
-			DevicePrimesPow2LastNine = lastDigitSharedTables.DevicePrimesPow2LastNine.View;
-
-			DivisorTables = HeuristicCombinedGpuTables
-				.GetStaticTables(acceleratorIndex)
-				.CreateViews();
-
-			var smallPrimeFactorTables = SmallPrimeFactorGpuTables.GetStaticTables(acceleratorIndex);
-
-			if (smallPrimeFactorTables.HasValue)
-			{
-				SmallPrimeFactorGpuTables tables = smallPrimeFactorTables.Value;
-				SmallPrimeFactorPrimes = tables.Primes.View;
-				SmallPrimeFactorSquares = tables.Squares.View;
-			}
-
-			CheckFactorsKernelLauncher = KernelUtil.GetKernel(accelerator.LoadStreamKernel<int, ulong, ArrayView1D<KeyValuePair<ulong, int>, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>(PrimeOrderGpuHeuristics.CheckFactorsKernel)).CreateLauncherDelegate<Action<AcceleratorStream, int, ulong, ArrayView1D<KeyValuePair<ulong, int>, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>>();
-
-			ConvertToStandardKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>(Pow2MontgomeryKernels.Pow2MontgomeryKernelConvertToStandard)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>>();
-
-			HeuristicCombinedTrialDivisionKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, byte, ArrayView<int>, ulong, ulong, HeuristicCombinedGpuViews>(PrimeTesterKernels.HeuristicTrialCombinedDivisionKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, byte, ArrayView<int>, ulong, ulong, HeuristicCombinedGpuViews>>();
-
-			KeepMontgomeryKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>(Pow2MontgomeryKernels.Pow2MontgomeryKernelKeepMontgomery)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>>();
-
-			PollardRhoKernelLauncher = KernelUtil.GetKernel(accelerator.LoadStreamKernel<ulong, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2MontgomeryKernels.TryPollardRhoKernel)).CreateLauncherDelegate<Action<AcceleratorStream, ulong, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
-
-			Pow2ModWideKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>>(PrimeOrderGpuHeuristics.Pow2ModKernelWide)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>>>();
-
-			SharesFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<byte>>(PrimeTesterKernels.SharesFactorKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<byte>>>();
-
-			SmallPrimeFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(SmallPrimeFactorKernels.SmallPrimeFactorKernelScan)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
-
-			SmallPrimeSieveKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>>(PrimeTesterKernels.SmallPrimeSieveKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<uint>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>>>();
-
-			SpecialMaxKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(PrimeOrderGpuHeuristics.EvaluateSpecialMaxCandidatesKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
-		}
-	}
-
-	public void Dispose()
-	{
-		Input.Dispose();
-		OutputByte.Dispose();
-		OutputInt.Dispose();
-		OutputUlong.Dispose();
-		Pow2ModEntriesToTestOnDevice.Dispose();
-		SmallPrimeFactorCountSlot.Dispose();
-		SpecialMaxResult.Dispose();
-
-		// These resources are shared between GPU leases
-		// Stream.Dispose();
-		// Accelerator.Dispose();
-		// Context.Dispose();
-	}
-}

PerfectNumbers.Core/Gpu/DeterministicRandomGpu.cs

@@ -1,75 +0,0 @@
-using System.Runtime.CompilerServices;
-using ILGPU;
-
-namespace PerfectNumbers.Core.Gpu;
-
-public static class ThreadStaticDeterministicRandomGpu
-{
-	[ThreadStatic]
-	private static DeterministicRandomGpu? _exclusive;
-	internal static DeterministicRandomGpu Exclusive => _exclusive ?? new DeterministicRandomGpu();
-}
-
-internal struct DeterministicRandomGpu
-{
-	private static long s_seedCounter;
-
-	private ulong _state;
-	public readonly ulong State
-	{
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		get
-		{
-			return _state;
-		}
-	}
-
-	public DeterministicRandomGpu()
-	{
-		_state = CreateThreadState();
-	}
-
-	public DeterministicRandomGpu(ulong initialState)
-	{
-		_state = initialState;
-	}
-
-	public ulong NextUInt64()
-	{
-		ulong state = _state;
-		state ^= state >> 12;
-		state ^= state << 25;
-		state ^= state >> 27;
-		_state = state;
-		return state * 2685821657736338717UL;
-	}
-
-	public GpuUInt128 NextUInt128()
-	{
-		GpuUInt128 high = (GpuUInt128)NextUInt64();
-		ReadOnlyGpuUInt128 low = (ReadOnlyGpuUInt128)NextUInt64();
-		high.ShiftLeft(64);
-		high.Add(low);
-		return high;
-	}
-
-	public void SetState(ulong state)
-	{
-		_state = state;
-	}
-
-	private static ulong CreateThreadState()
-	{
-		ulong seed = (ulong)Atomic.Add(ref s_seedCounter, 1);
-		seed += 0x9E3779B97F4A7C15UL;
-		seed = (seed ^ (seed >> 30)) * 0xBF58476D1CE4E5B9UL;
-		seed = (seed ^ (seed >> 27)) * 0x94D049BB133111EBUL;
-		seed ^= seed >> 31;
-		if (seed == 0UL)
-		{
-			seed = 0x9E3779B97F4A7C15UL;
-		}
-
-		return seed;
-	}
-}

PerfectNumbers.Core/Gpu/ExponentRemainderStepperGpu.cs

@@ -1,4 +1,5 @@
 using System.Runtime.CompilerServices;
+using PerfectNumbers.Core;
 
 namespace PerfectNumbers.Core.Gpu;
 
@@ -23,14 +24,17 @@ internal struct ExponentRemainderStepperGpu
         _currentResidue = GpuUInt128.One;
     }
 
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	public readonly bool MatchesDivisor(in GpuDivisorPartialData divisor) => _modulus == divisor.Modulus;
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public bool MatchesDivisor(in GpuDivisorPartialData divisor)
+    {
+        return _modulus == divisor.Modulus;
+    }
 
-	/// <summary>
-	/// Clears the cached residue so the stepper can be reused for another divisor.
-	/// Callers must reinitialize the stepper before consuming any residues after a reset.
-	/// </summary>
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
+    /// <summary>
+    /// Clears the cached residue so the stepper can be reused for another divisor.
+    /// Callers must reinitialize the stepper before consuming any residues after a reset.
+    /// </summary>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public void Reset()
     {
         PreviousExponent = 0UL;

PerfectNumbers.Core/Gpu/GpuContextPool.cs

@@ -0,0 +1,163 @@
+using System.Collections.Concurrent;
+using ILGPU;
+using ILGPU.Runtime;
+
+namespace PerfectNumbers.Core.Gpu;
+
+public static class GpuContextPool
+{
+        private static readonly bool PoolingEnabled = true;
+        // The pool intentionally skips pre-loading ProcessEightBitWindows kernels so accelerator initialization
+        // stays stable; GpuKernelPool JIT-compiles them on first use alongside the small-cycle uploads.
+        // Default device preference for generic GPU kernels (prime scans, NTT, etc.)
+        public static bool ForceCpu { get; set; } = false;
+
+        internal sealed class PooledContext
+        {
+                private bool disposed;
+
+                public Context Context { get; }
+                public Accelerator Accelerator { get; }
+                public bool IsCpu { get; }
+                public object ExecutionLock { get; } = new();
+
+		public PooledContext(bool preferCpu)
+		{
+			Context = Context.CreateDefault();
+			Accelerator = Context.GetPreferredDevice(preferCpu).CreateAccelerator(Context);
+			IsCpu = Accelerator.AcceleratorType == AcceleratorType.CPU;
+			// NOTE: Avoid loading/compiling any kernel here to prevent implicit
+			// CL stream/queue creation during accelerator construction.
+			// Some OpenCL drivers are fragile when a queue is created immediately
+			// after device init. Real kernels will be JIT-loaded at first use.
+		}
+
+		public void Dispose()
+		{
+			if (disposed)
+			{
+				return;
+			}
+
+			// Ensure all cached GPU buffers for this accelerator are released.
+			NttGpuMath.ClearCaches(Accelerator);
+			// Release PrimeTester GPU state for this accelerator (kernel/device primes)
+			// Clear any per-accelerator cached resources to avoid releasing
+			// after the accelerator is destroyed.
+			PrimeTester.ClearGpuCaches(Accelerator);
+
+			Accelerator.Dispose();
+			Context.Dispose();
+			disposed = true;
+		}
+	}
+
+	private static readonly ConcurrentQueue<PooledContext> CpuPool = new();
+	private static readonly ConcurrentQueue<PooledContext> GpuPool = new();
+	private static readonly object CreationLock = new();
+
+	public static GpuContextLease Rent()
+	{
+		return RentPreferred(ForceCpu);
+	}
+
+	// Allows callers to choose CPU/GPU per use-case, decoupled from ForceCpu.
+	public static GpuContextLease RentPreferred(bool preferCpu)
+	{
+		if (PoolingEnabled)
+		{
+			if (preferCpu && CpuPool.TryDequeue(out var cpu))
+			{
+				return new GpuContextLease(cpu, CreationLock);
+			}
+
+			if (!preferCpu && GpuPool.TryDequeue(out var gpu))
+			{
+				return new GpuContextLease(gpu, CreationLock);
+			}
+		}
+
+		// Serialize accelerator creation to avoid concurrent CL device/stream setup across threads.
+		lock (CreationLock)
+		{
+			return new GpuContextLease(new PooledContext(preferCpu), CreationLock);
+		}
+	}
+
+	public static void DisposeAll()
+	{
+		if (!PoolingEnabled)
+		{
+			return;
+		}
+
+		while (CpuPool.TryDequeue(out var cpu))
+		{
+			cpu.Dispose();
+		}
+
+		while (GpuPool.TryDequeue(out var gpu))
+		{
+			gpu.Dispose();
+		}
+
+		PrimeTester.DisposeGpuContexts();
+	}
+
+	private static void Return(PooledContext ctx)
+	{
+		if (PoolingEnabled)
+		{
+			ctx.Accelerator.Synchronize();
+			if (ctx.IsCpu)
+			{
+				CpuPool.Enqueue(ctx);
+			}
+			else
+			{
+				GpuPool.Enqueue(ctx);
+			}
+		}
+
+                else
+                {
+                        lock (CreationLock)
+                        {
+                                ctx.Dispose();
+                        }
+                }
+        }
+
+    public struct GpuContextLease
+    {
+        private readonly PooledContext _ctx;
+                private bool disposed;
+
+                internal GpuContextLease(PooledContext ctx, object kernelInitLock)
+        {
+            _ctx = ctx;
+                        KernelInitLock = kernelInitLock;
+                }
+
+        public Context Context => _ctx.Context;
+
+        public Accelerator Accelerator => _ctx.Accelerator;
+
+                public object KernelInitLock { get; }
+
+                public object ExecutionLock => _ctx.ExecutionLock;
+
+
+                public void Dispose()
+                {
+                        if (disposed)
+			{
+				return;
+			}
+
+			Return(_ctx);
+			disposed = true;
+        }
+    }
+}
+

PerfectNumbers.Core/Gpu/GpuKernelLease.cs

@@ -0,0 +1,213 @@
+using System.Collections.Concurrent;
+using ILGPU;
+using ILGPU.Runtime;
+using static PerfectNumbers.Core.Gpu.GpuContextPool;
+
+namespace PerfectNumbers.Core.Gpu;
+
+public sealed class GpuKernelLease
+{
+    private static readonly ConcurrentQueue<GpuKernelLease> Pool = new();
+
+    private IDisposable? _limiter;
+    private GpuContextLease? _gpu;
+    private KernelContainer? _kernels;
+    private AcceleratorStream? _stream;
+    private object? _executionLock;
+    private bool _disposed;
+
+    private GpuKernelLease()
+    {
+    }
+
+    internal static GpuKernelLease Rent(IDisposable limiter, GpuContextLease gpu, KernelContainer kernels)
+    {
+        if (!Pool.TryDequeue(out var lease))
+        {
+            lease = new GpuKernelLease();
+        }
+
+        lease._limiter = limiter;
+        lease._gpu = gpu;
+        lease._kernels = kernels;
+        lease._stream = null;
+        lease._executionLock = gpu.ExecutionLock;
+        lease._disposed = false;
+        return lease;
+    }
+
+    public Accelerator Accelerator => _gpu?.Accelerator ?? throw new NullReferenceException("GPU context is already released");
+
+    public AcceleratorStream Stream
+    {
+        get
+        {
+            if (_stream is { } stream)
+            {
+                return stream;
+            }
+
+            // It feels that we can combine these into 1 return statement, but that increases the max stack frame size to 3 from 2
+            stream = Accelerator.CreateStream();
+            _stream = stream;
+            return stream;
+        }
+    }
+
+    public ExecutionScope EnterExecutionScope() => new ExecutionScope(_executionLock);
+
+    public Action<AcceleratorStream, Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>> OrderKernel
+    {
+        get
+        {
+            var accel = Accelerator; // avoid capturing 'this' in lambda
+            lock (_gpu!.Value.KernelInitLock)
+            {
+                return KernelContainer.InitOnce(ref _kernels!.Order, () =>
+                {
+                    var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>(OrderKernels.OrderKernelScan);
+                    var kernel = KernelUtil.GetKernel(loaded);
+                    return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>>();
+                });
+            }
+        }
+    }
+
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> Pow2ModKernel
+    {
+        get
+        {
+            var accel = Accelerator;
+            lock (_gpu!.Value.KernelInitLock)
+            {
+                return KernelContainer.InitOnce(ref _kernels!.Pow2Mod, () =>
+                {
+                    var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2ModKernels.Pow2ModKernelScan);
+                    var kernel = KernelUtil.GetKernel(loaded);
+                    return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
+                });
+            }
+        }
+    }
+
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>> IncrementalKernel
+    {
+        get
+        {
+            var accel = Accelerator;
+            lock (_gpu!.Value.KernelInitLock)
+            {
+                return KernelContainer.InitOnce(ref _kernels!.Incremental, () =>
+                {
+                    var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>>(IncrementalKernels.IncrementalKernelScan);
+                    var kernel = KernelUtil.GetKernel(loaded);
+                    return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>>>();
+                });
+            }
+        }
+    }
+
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>> IncrementalOrderKernel
+    {
+        get
+        {
+            var accel = Accelerator;
+            lock (_gpu!.Value.KernelInitLock)
+            {
+                return KernelContainer.InitOnce(ref _kernels!.IncrementalOrder, () =>
+                {
+                    var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>(IncrementalKernels.IncrementalOrderKernelScan);
+                    var kernel = KernelUtil.GetKernel(loaded);
+                    return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>>();
+                });
+            }
+        }
+    }
+
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>> Pow2ModOrderKernel
+    {
+        get
+        {
+            var accel = Accelerator;
+            lock (_gpu!.Value.KernelInitLock)
+            {
+                return KernelContainer.InitOnce(ref _kernels!.Pow2ModOrder, () =>
+                {
+                    var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2ModKernels.Pow2ModOrderKernelScan);
+                    var kernel = KernelUtil.GetKernel(loaded);
+                    return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>>();
+                });
+            }
+        }
+    }
+
+    public Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> SmallPrimeFactorKernel
+    {
+        get
+        {
+            var accel = Accelerator;
+            lock (_gpu!.Value.KernelInitLock)
+            {
+                return KernelContainer.InitOnce(ref _kernels!.SmallPrimeFactor, () =>
+                {
+                    var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(SmallPrimeFactorKernels.SmallPrimeFactorKernelScan);
+                    var kernel = KernelUtil.GetKernel(loaded);
+                    return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
+                });
+            }
+        }
+    }
+
+    private void Dispose(bool disposing)
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        if (disposing)
+        {
+            _stream?.Dispose();
+            _stream = null;
+
+            _gpu?.Dispose();
+            _gpu = null;
+
+            _executionLock = null;
+
+            _limiter?.Dispose();
+            _limiter = null;
+        }
+
+        _kernels = null;
+        _disposed = true;
+        Pool.Enqueue(this);
+    }
+
+    public void Dispose()
+    {
+        Dispose(disposing: false);
+    }
+
+    public readonly struct ExecutionScope
+    {
+        private readonly object? _lock;
+
+        public ExecutionScope(object? sync)
+        {
+            _lock = sync;
+            if (_lock is not null)
+            {
+                Monitor.Enter(_lock);
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_lock is not null)
+            {
+                Monitor.Exit(_lock);
+            }
+        }
+    }
+}

PerfectNumbers.Core/Gpu/GpuKernelPool.cs

@@ -1,232 +1,305 @@
+using System.Collections.Concurrent;
 using ILGPU;
 using ILGPU.Runtime;
-using PerfectNumbers.Core.Gpu.Accelerators;
+using static PerfectNumbers.Core.Gpu.GpuContextPool;
 
 namespace PerfectNumbers.Core.Gpu;
 
+public readonly struct ResidueAutomatonArgs
+{
+    public readonly ulong Q0M10;
+    public readonly ulong Step10;
+    public readonly ulong Q0M8;
+    public readonly ulong Step8;
+    public readonly ulong Q0M3;
+    public readonly ulong Step3;
+    public readonly ulong Q0M5;
+    public readonly ulong Step5;
+
+    public ResidueAutomatonArgs(ulong q0m10, ulong step10, ulong q0m8, ulong step8, ulong q0m3, ulong step3, ulong q0m5, ulong step5)
+    {
+        Q0M10 = q0m10; Step10 = step10; Q0M8 = q0m8; Step8 = step8; Q0M3 = q0m3; Step3 = step3; Q0M5 = q0m5; Step5 = step5;
+    }
+}
+
+public sealed class KernelContainer
+{
+    // Serializes first-time initialization of kernels/buffers per accelerator.
+    public Action<AcceleratorStream, Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>? Order;
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
+    ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>>? Incremental;
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
+        ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>,
+        ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>,
+        ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>? Pow2Mod;
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
+            ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>? IncrementalOrder;
+    public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
+        ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>? Pow2ModOrder;
+    public Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>? SmallPrimeFactor;
+
+    // Optional device buffer with small divisor cycles (<= 4M). Index = divisor, value = cycle length.
+    public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallCycles;
+    public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimeFactorsPrimes;
+    public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimeFactorsSquares;
+    public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimeFactorPrimeSlots;
+    public MemoryBuffer1D<int, Stride1D.Dense>? SmallPrimeFactorExponentSlots;
+    public MemoryBuffer1D<int, Stride1D.Dense>? SmallPrimeFactorCountSlot;
+    public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimeFactorRemainingSlot;
+    public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastOne;
+    public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastOne;
+    public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastSeven;
+    public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastSeven;
+
+    public static T InitOnce<T>(ref T? slot, Func<T> factory) where T : class
+    {
+        var current = Volatile.Read(ref slot);
+        if (current is not null)
+        {
+            return current;
+        }
+
+        current = Volatile.Read(ref slot);
+        if (current is null)
+        {
+            current = factory();
+            Volatile.Write(ref slot, current);
+        }
+        return current;
+    }
+}
+
+public readonly struct ResiduePrimeViews(
+    ArrayView1D<uint, Stride1D.Dense> lastOne,
+    ArrayView1D<uint, Stride1D.Dense> lastSeven,
+    ArrayView1D<ulong, Stride1D.Dense> lastOnePow2,
+    ArrayView1D<ulong, Stride1D.Dense> lastSevenPow2)
+{
+    public readonly ArrayView1D<uint, Stride1D.Dense> LastOne = lastOne;
+    public readonly ArrayView1D<uint, Stride1D.Dense> LastSeven = lastSeven;
+    public readonly ArrayView1D<ulong, Stride1D.Dense> LastOnePow2 = lastOnePow2;
+    public readonly ArrayView1D<ulong, Stride1D.Dense> LastSevenPow2 = lastSevenPow2;
+}
+
+public readonly struct SmallPrimeFactorTables
+{
+    public readonly MemoryBuffer1D<uint, Stride1D.Dense> Primes;
+    public readonly MemoryBuffer1D<ulong, Stride1D.Dense> Squares;
+    public readonly int Count;
+
+    public SmallPrimeFactorTables(
+        MemoryBuffer1D<uint, Stride1D.Dense> primes,
+        MemoryBuffer1D<ulong, Stride1D.Dense> squares,
+        int count)
+    {
+        Primes = primes;
+        Squares = squares;
+        Count = count;
+    }
+
+    public ArrayView1D<uint, Stride1D.Dense> PrimesView => Primes.View;
+    public ArrayView1D<ulong, Stride1D.Dense> SquaresView => Squares.View;
+}
+
+public readonly struct SmallPrimeFactorScratch
+{
+    public readonly MemoryBuffer1D<ulong, Stride1D.Dense> PrimeSlots;
+    public readonly MemoryBuffer1D<int, Stride1D.Dense> ExponentSlots;
+    public readonly MemoryBuffer1D<int, Stride1D.Dense> CountSlot;
+    public readonly MemoryBuffer1D<ulong, Stride1D.Dense> RemainingSlot;
+
+    public SmallPrimeFactorScratch(
+        MemoryBuffer1D<ulong, Stride1D.Dense> primeSlots,
+        MemoryBuffer1D<int, Stride1D.Dense> exponentSlots,
+        MemoryBuffer1D<int, Stride1D.Dense> countSlot,
+        MemoryBuffer1D<ulong, Stride1D.Dense> remainingSlot)
+    {
+        PrimeSlots = primeSlots;
+        ExponentSlots = exponentSlots;
+        CountSlot = countSlot;
+        RemainingSlot = remainingSlot;
+    }
+
+    public void Clear()
+    {
+        PrimeSlots.MemSetToZero();
+        ExponentSlots.MemSetToZero();
+        CountSlot.MemSetToZero();
+        RemainingSlot.MemSetToZero();
+    }
+}
+
 public class GpuKernelPool
 {
-	[ThreadStatic]
-	private static KernelContainer[]? _pool;
+    private static readonly ConcurrentDictionary<Accelerator, KernelContainer> KernelCache = new(); // TODO: Replace this concurrent map with a simple accelerator-indexed lookup once kernel launchers are prewarmed during startup so we can drop the thread-safe wrapper entirely.
 
-	public static T InitOnce<T>(ref T? target, Func<T> valueFactory) where T : class
-	{
-		if (target is { } value)
-		{
-			return value;
-		}
+    private static KernelContainer GetKernels(Accelerator accelerator)
+    {
+        return KernelCache.GetOrAdd(accelerator, _ => new KernelContainer());
+    }
 
-		var newValue = valueFactory();
-		return Interlocked.CompareExchange(ref target, newValue, null) ?? newValue;
-	}
+    // Ensures the small cycles table is uploaded to the device for the given accelerator.
+    // Returns the ArrayView to pass into kernels (when kernels are extended to accept it).
+    public static ArrayView1D<ulong, Stride1D.Dense> EnsureSmallCyclesOnDevice(Accelerator accelerator)
+    {
+        var kernels = GetKernels(accelerator);
+        if (kernels.SmallCycles is { } buffer)
+        {
+            return buffer.View;
+        }
 
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
+        // Ensure single upload per accelerator even if multiple threads race here.
+        lock (kernels) // TODO: Remove this lock by pre-uploading the immutable small-cycle snapshot during initialization; once no mutation happens at runtime, the pool must expose a simple reference without synchronization.
+        {
+            if (kernels.SmallCycles is { } existing)
+            {
+                return existing.View;
+            }
 
+            var host = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot(); // TODO: Preload this device buffer during startup and keep it immutable so we can delete the lock above in favor of the preloaded snapshot.
+            var device = accelerator.Allocate1D<ulong>(host.Length);
+            device.View.CopyFromCPU(host);
+            kernels.SmallCycles = device;
+            return device.View;
+        }
+    }
 
-	internal static KernelContainer GetOrAddKernels(int acceleratorIndex, AcceleratorStream stream, KernelType kernelType)
-	{
-		var pool = _pool ??= [];
-		if (pool[acceleratorIndex] is not { } kernels)
-		{
-			kernels = new();
-		}
+    public static ResiduePrimeViews EnsureSmallPrimesOnDevice(Accelerator accelerator)
+    {
+        var kernels = GetKernels(accelerator);
+        if (kernels.SmallPrimesLastOne is { } lastOne &&
+            kernels.SmallPrimesLastSeven is { } lastSeven &&
+            kernels.SmallPrimesPow2LastOne is { } lastOnePow2 &&
+            kernels.SmallPrimesPow2LastSeven is { } lastSevenPow2)
+        {
+            return new ResiduePrimeViews(lastOne.View, lastSeven.View, lastOnePow2.View, lastSevenPow2.View);
+        }
 
-		Accelerator accelerator = _accelerators[acceleratorIndex];
-		if (kernelType.HasFlag(KernelType.OrderKernelScan))
-		{
-			InitOrderKernelScan(accelerator, kernels);
-		}
+        lock (kernels) // TODO: Inline these small-prime uploads into startup initialization alongside the small-cycle snapshot so we can drop runtime locking and keep the GPU pool free of synchronization.
+        {
+            if (kernels.SmallPrimesLastOne is { } existingLastOne &&
+                kernels.SmallPrimesLastSeven is { } existingLastSeven &&
+                kernels.SmallPrimesPow2LastOne is { } existingLastOnePow2 &&
+                kernels.SmallPrimesPow2LastSeven is { } existingLastSevenPow2)
+            {
+                return new ResiduePrimeViews(existingLastOne.View, existingLastSeven.View, existingLastOnePow2.View, existingLastSevenPow2.View);
+            }
 
-		if (kernelType.HasFlag(KernelType.Pow2ModKernelScan))
-		{
-			InitPow2ModKernelScan(accelerator, kernels);
-		}
+            var hostLastOne = PrimesGenerator.SmallPrimesLastOne;
+            var hostLastSeven = PrimesGenerator.SmallPrimesLastSeven;
+            var hostLastOnePow2 = PrimesGenerator.SmallPrimesPow2LastOne;
+            var hostLastSevenPow2 = PrimesGenerator.SmallPrimesPow2LastSeven;
 
-		if (kernelType.HasFlag(KernelType.IncrementalKernelScan))
-		{
-			InitIncrementalKernelScan(accelerator, kernels);
-		}
+            var deviceLastOne = accelerator.Allocate1D<uint>(hostLastOne.Length);
+            deviceLastOne.View.CopyFromCPU(hostLastOne);
+            var deviceLastSeven = accelerator.Allocate1D<uint>(hostLastSeven.Length);
+            deviceLastSeven.View.CopyFromCPU(hostLastSeven);
+            var deviceLastOnePow2 = accelerator.Allocate1D<ulong>(hostLastOnePow2.Length);
+            deviceLastOnePow2.View.CopyFromCPU(hostLastOnePow2);
+            var deviceLastSevenPow2 = accelerator.Allocate1D<ulong>(hostLastSevenPow2.Length);
+            deviceLastSevenPow2.View.CopyFromCPU(hostLastSevenPow2);
 
-		if (kernelType.HasFlag(KernelType.IncrementalOrderKernelScan))
-		{
-			IncrementalOrderKernelScan(accelerator, kernels);
-		}
+            kernels.SmallPrimesLastOne = deviceLastOne;
+            kernels.SmallPrimesLastSeven = deviceLastSeven;
+            kernels.SmallPrimesPow2LastOne = deviceLastOnePow2;
+            kernels.SmallPrimesPow2LastSeven = deviceLastSevenPow2;
 
-		if (kernelType.HasFlag(KernelType.Pow2ModOrderKernelScan))
-		{
-			InitPow2ModOrderKernelScan(accelerator, kernels);
-		}
+            return new ResiduePrimeViews(deviceLastOne.View, deviceLastSeven.View, deviceLastOnePow2.View, deviceLastSevenPow2.View);
+        }
+    }
 
-		PreloadStaticTables(accelerator, kernels, stream, kernelType);
+    public static SmallPrimeFactorTables EnsureSmallPrimeFactorTables(Accelerator accelerator)
+    {
+        var kernels = GetKernels(accelerator);
+        if (kernels.SmallPrimeFactorsPrimes is { } primeBuffer && kernels.SmallPrimeFactorsSquares is { } squareBuffer)
+        {
+            return new SmallPrimeFactorTables(primeBuffer, squareBuffer, (int)primeBuffer.Length);
+        }
 
-		pool[acceleratorIndex] = kernels;
-		return kernels;
+        lock (kernels)
+        {
+            if (kernels.SmallPrimeFactorsPrimes is { } existingPrimes && kernels.SmallPrimeFactorsSquares is { } existingSquares)
+            {
+                return new SmallPrimeFactorTables(existingPrimes, existingSquares, (int)existingPrimes.Length);
+            }
 
-		static void InitOrderKernelScan(Accelerator accelerator, KernelContainer kernels)
-		{
-			InitOnce(ref kernels.Order, () =>
-			{
-				var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>(OrderKernels.OrderKernelScan);
+            var hostPrimes = PrimesGenerator.SmallPrimes;
+            var hostSquares = PrimesGenerator.SmallPrimesPow2;
 
-				var kernel = KernelUtil.GetKernel(loaded);
+            var devicePrimes = accelerator.Allocate1D<uint>(hostPrimes.Length);
+            devicePrimes.View.CopyFromCPU(hostPrimes);
+            var deviceSquares = accelerator.Allocate1D<ulong>(hostSquares.Length);
+            deviceSquares.View.CopyFromCPU(hostSquares);
 
-				return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>>();
-			});
-		}
+            kernels.SmallPrimeFactorsPrimes = devicePrimes;
+            kernels.SmallPrimeFactorsSquares = deviceSquares;
 
-		static void InitPow2ModKernelScan(Accelerator accelerator, KernelContainer kernels)
-		{
-			InitOnce(ref kernels.Pow2Mod, () =>
-			{
-				var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2ModKernels.Pow2ModKernelScan);
+            return new SmallPrimeFactorTables(devicePrimes, deviceSquares, hostPrimes.Length);
+        }
+    }
 
-				var kernel = KernelUtil.GetKernel(loaded);
+    public static SmallPrimeFactorScratch EnsureSmallPrimeFactorScratch(Accelerator accelerator, int slotCount)
+    {
+        var kernels = GetKernels(accelerator);
+        lock (kernels)
+        {
+            MemoryBuffer1D<ulong, Stride1D.Dense>? primeSlots = kernels.SmallPrimeFactorPrimeSlots;
+            if (primeSlots is null || primeSlots.Length < slotCount)
+            {
+                primeSlots?.Dispose();
+                primeSlots = accelerator.Allocate1D<ulong>(slotCount);
+                kernels.SmallPrimeFactorPrimeSlots = primeSlots;
+            }
 
-				return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
-			});
-		}
+            MemoryBuffer1D<int, Stride1D.Dense>? exponentSlots = kernels.SmallPrimeFactorExponentSlots;
+            if (exponentSlots is null || exponentSlots.Length < slotCount)
+            {
+                exponentSlots?.Dispose();
+                exponentSlots = accelerator.Allocate1D<int>(slotCount);
+                kernels.SmallPrimeFactorExponentSlots = exponentSlots;
+            }
 
-		static void InitIncrementalKernelScan(Accelerator accelerator, KernelContainer kernels)
-		{
-			InitOnce(ref kernels.Incremental, () =>
-			{
-				var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>>(IncrementalKernels.IncrementalKernelScan);
+            MemoryBuffer1D<int, Stride1D.Dense>? countSlot = kernels.SmallPrimeFactorCountSlot;
+            if (countSlot is null)
+            {
+                countSlot = accelerator.Allocate1D<int>(1);
+                kernels.SmallPrimeFactorCountSlot = countSlot;
+            }
 
-				var kernel = KernelUtil.GetKernel(loaded);
+            MemoryBuffer1D<ulong, Stride1D.Dense>? remainingSlot = kernels.SmallPrimeFactorRemainingSlot;
+            if (remainingSlot is null)
+            {
+                remainingSlot = accelerator.Allocate1D<ulong>(1);
+                kernels.SmallPrimeFactorRemainingSlot = remainingSlot;
+            }
 
-				return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>>>();
-			});
-		}
+            return new SmallPrimeFactorScratch(primeSlots!, exponentSlots!, countSlot!, remainingSlot!);
+        }
+    }
 
-		static void IncrementalOrderKernelScan(Accelerator accelerator, KernelContainer kernels)
-		{
-			InitOnce(ref kernels.IncrementalOrder, () =>
-			{
-				var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>(IncrementalKernels.IncrementalOrderKernelScan);
+    public static GpuKernelLease GetKernel(bool useGpuOrder)
+    {
+        var limiter = GpuPrimeWorkLimiter.Acquire();
+        var gpu = RentPreferred(preferCpu: !useGpuOrder);
+        var accelerator = gpu.Accelerator;
+        var kernels = GetKernels(accelerator);
+        return GpuKernelLease.Rent(limiter, gpu, kernels);
+    }
 
-				var kernel = KernelUtil.GetKernel(loaded);
+    /// <summary>
+    /// Runs a GPU action with an acquired accelerator and stream.
+    /// </summary>
+    /// <param name="action">Action to run with (Accelerator, Stream).</param>
+    public static void Run(Action<Accelerator, AcceleratorStream> action)
+    {
+        var lease = GetKernel(useGpuOrder: true);
+        var execution = lease.EnterExecutionScope();
+        var accelerator = lease.Accelerator;
+        var stream = accelerator.CreateStream();
+        action(accelerator, stream);
+        stream.Dispose();
+        execution.Dispose();
+        lease.Dispose();
 
-				return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte,
-				ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>>();
-			});
-		}
-
-		static void InitPow2ModOrderKernelScan(Accelerator accelerator, KernelContainer kernels)
-		{
-			InitOnce(ref kernels.Pow2ModOrder, () =>
-			{
-				var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2ModKernels.Pow2ModOrderKernelScan);
-
-				var kernel = KernelUtil.GetKernel(loaded);
-
-				return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong, ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>>();
-			});
-		}
-	}
-
-	internal static void PreloadStaticTables(Accelerator accelerator, KernelContainer kernels, AcceleratorStream stream, KernelType kernelType)
-	{
-		if (kernelType.HasFlag(KernelType.SmallCycles))
-		{
-			EnsureSmallCyclesOnDevice(accelerator, kernels, stream);
-		}
-
-		if (kernelType.HasFlag(KernelType.SmallPrimes))
-		{
-			EnsureSmallPrimesOnDevice(accelerator, kernels, stream);
-		}
-	}
-
-	public static ArrayView1D<ulong, Stride1D.Dense> GetSmallCyclesOnDevice(KernelContainer kernels) => kernels.SmallCycles!;
-
-	// Ensures the small cycles table is uploaded to the device for the given accelerator.
-	// Returns the ArrayView to pass into kernels (when kernels are extended to accept it).
-	private static void EnsureSmallCyclesOnDevice(Accelerator accelerator, KernelContainer kernels, AcceleratorStream stream)
-	{
-		if (kernels.SmallCycles is { })
-		{
-			return;
-		}
-
-		var host = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
-		MemoryBuffer1D<ulong, Stride1D.Dense>? device;
-
-		lock (accelerator)
-		{
-			device = accelerator.Allocate1D<ulong>(host.Length);
-		}
-
-		device.View.CopyFromCPU(stream, host);
-		kernels.SmallCycles = device;
-	}
-
-	public static ResiduePrimeViews GetSmallPrimesOnDevice(KernelContainer kernels) => new(
-		kernels.SmallPrimesLastOne!,
-		kernels.SmallPrimesLastSeven!,
-		kernels.SmallPrimesPow2LastOne!,
-		kernels.SmallPrimesPow2LastSeven!
-	);
-
-	private static void EnsureSmallPrimesOnDevice(Accelerator accelerator, KernelContainer kernels, AcceleratorStream stream)
-	{
-		if (kernels.SmallPrimesLastOne is { } &&
-			kernels.SmallPrimesLastSeven is { } &&
-			kernels.SmallPrimesPow2LastOne is { } &&
-			kernels.SmallPrimesPow2LastSeven is { })
-		{
-			return;
-		}
-
-		if (kernels.SmallPrimesLastOne is { } &&
-			kernels.SmallPrimesLastSeven is { } &&
-			kernels.SmallPrimesPow2LastOne is { } &&
-			kernels.SmallPrimesPow2LastSeven is { })
-		{
-			return;
-		}
-
-		var hostLastOne = PrimesGenerator.SmallPrimesLastOne;
-		var hostLastSeven = PrimesGenerator.SmallPrimesLastSeven;
-		var hostLastOnePow2 = PrimesGenerator.SmallPrimesPow2LastOne;
-		var hostLastSevenPow2 = PrimesGenerator.SmallPrimesPow2LastSeven;
-
-		MemoryBuffer1D<uint, Stride1D.Dense>? deviceLastOne;
-		MemoryBuffer1D<uint, Stride1D.Dense>? deviceLastSeven;
-		MemoryBuffer1D<ulong, Stride1D.Dense>? deviceLastOnePow2;
-		MemoryBuffer1D<ulong, Stride1D.Dense>? deviceLastSevenPow2;
-
-		lock (accelerator)
-		{
-			deviceLastOne = accelerator.Allocate1D<uint>(hostLastOne.Length);
-			deviceLastSeven = accelerator.Allocate1D<uint>(hostLastSeven.Length);
-			deviceLastOnePow2 = accelerator.Allocate1D<ulong>(hostLastOnePow2.Length);
-			deviceLastSevenPow2 = accelerator.Allocate1D<ulong>(hostLastSevenPow2.Length);
-		}
-
-		deviceLastOne.View.CopyFromCPU(stream, hostLastOne);
-		deviceLastSeven.View.CopyFromCPU(stream, hostLastSeven);
-		deviceLastOnePow2.View.CopyFromCPU(stream, hostLastOnePow2);
-		deviceLastSevenPow2.View.CopyFromCPU(stream, hostLastSevenPow2);
-		kernels.SmallPrimesLastOne = deviceLastOne;
-		kernels.SmallPrimesLastSeven = deviceLastSeven;
-		kernels.SmallPrimesPow2LastOne = deviceLastOnePow2;
-		kernels.SmallPrimesPow2LastSeven = deviceLastSevenPow2;
-	}
-
-	/// <summary>
-	/// Runs a GPU action with an acquired accelerator and stream.
-	/// </summary>
-	/// <param name="action">Action to run with (Accelerator, Stream).</param>
-	public static void Run(Action<Accelerator, AcceleratorStream> action)
-	{
-		// GpuPrimeWorkLimiter.Acquire();
-		var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		var accelerator = _accelerators[acceleratorIndex];
-		var stream = AcceleratorStreamPool.Rent(acceleratorIndex);
-		action(accelerator, stream);
-		stream.Synchronize();
-		stream.Dispose();
-		accelerator.Dispose();
-		// GpuPrimeWorkLimiter.Release();
-	}
+    }
 }

PerfectNumbers.Core/Gpu/GpuPrimeWorkLimiter.cs

@@ -2,29 +2,60 @@ namespace PerfectNumbers.Core.Gpu;
 
 public static class GpuPrimeWorkLimiter
 {
-	private static SemaphoreSlim _semaphore = new(1, int.MaxValue);
-	private static int _currentLimit = 1;
+    private static SemaphoreSlim _semaphore = new(1, int.MaxValue);
+    private static readonly object _lock = new();
+    private static int _currentLimit = 1;
 
-	public static void Acquire() { } // => _semaphore.Wait();
-	public static void Release() { }// => _semaphore.Release();
-
-	public static void SetLimit(int value)
+    public static IDisposable Acquire()
     {
-        if (value <= 0)
+        // TODO: Inline the pooled limiter guard from the GpuLimiterThroughputBenchmarks so prime-sieve
+        // GPU jobs stop allocating Releaser instances on every acquisition.
+        var sem = _semaphore;
+        sem.Wait();
+        return new Releaser(sem);
+    }
+
+    public static void SetLimit(int value)
+    {
+        if (value < 1)
         {
             value = 1;
         }
 
-        if (value == _currentLimit)
+        lock (_lock)
         {
-            return;
+            if (value == _currentLimit)
+            {
+                return;
+            }
+
+            // TODO: Switch to a shared limiter implementation with GpuWorkLimiter so we can coordinate CPU/GPU prime work using
+            // the same semaphore pool without reallocating per adjustment.
+            _semaphore = new SemaphoreSlim(value, value);
+            _currentLimit = value;
+        }
+    }
+
+    private sealed class Releaser : IDisposable
+    {
+        private readonly SemaphoreSlim _sem;
+        private bool _disposed;
+
+        public Releaser(SemaphoreSlim sem)
+        {
+            _sem = sem;
         }
 
-        // TODO: Switch to a shared limiter implementation with GpuWorkLimiter so we can coordinate CPU/GPU prime work using
-        // the same semaphore pool without reallocating per adjustment.
-        var previous = _semaphore;
-        _semaphore = new SemaphoreSlim(value, value);
-        _currentLimit = value;
-        previous.Dispose();
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            _sem.Release();
+            _disposed = true;
+        }
     }
 }
+

PerfectNumbers.Core/Gpu/GpuUInt128.cs

@@ -261,13 +261,13 @@ public struct GpuUInt128 : IComparable<GpuUInt128>, IEquatable<GpuUInt128>
     public override readonly int GetHashCode() => HashCode.Combine(High, Low);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void Add(in ReadOnlyGpuUInt128 other) => Add(other.High, other.Low);
+    public void Add(in ReadOnlyGpuUInt128 other) => AddInternal(other.High, other.Low);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void Add(GpuUInt128 other) => Add(other.High, other.Low);
+    public void Add(GpuUInt128 other) => AddInternal(other.High, other.Low);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void Add(ulong otherHigh, ulong otherLow)
+    private void AddInternal(ulong otherHigh, ulong otherLow)
     {
         ulong originalLow = Low;
         // We're reusing originalLow for carry to avoid an extra local.
@@ -316,7 +316,7 @@ public struct GpuUInt128 : IComparable<GpuUInt128>, IEquatable<GpuUInt128>
             return;
         }
 
-        Add(valueHigh, valueLow);
+        AddInternal(valueHigh, valueLow);
         if (CompareTo(in modulus) >= 0)
         {
             Sub(in modulus);
@@ -589,6 +589,9 @@ public struct GpuUInt128 : IComparable<GpuUInt128>, IEquatable<GpuUInt128>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static GpuUInt128 BinaryGcd(GpuUInt128 u, GpuUInt128 v)
     {
+        // TODO: Replace this scalar binary GCD with the branchless reduction from
+        // GpuUInt128BinaryGcdBenchmarks so CPU fallbacks stay aligned with the GPU kernel
+        // performance when resolving large divisor residues.
         if (u.IsZero)
         {
             return v;
@@ -599,50 +602,26 @@ public struct GpuUInt128 : IComparable<GpuUInt128>, IEquatable<GpuUInt128>
             return u;
         }
 
-        ulong combinedLow = u.Low | v.Low;
-        int shift;
-        if (combinedLow != 0UL)
-        {
-            shift = BitOperations.TrailingZeroCount(combinedLow);
-        }
-        else
-        {
-            ulong combinedHigh = u.High | v.High;
-            shift = 64 + BitOperations.TrailingZeroCount(combinedHigh);
-        }
-
+        int shift = TrailingZeroCount(new GpuUInt128(u.High | v.High, u.Low | v.Low));
         int zu = TrailingZeroCount(u);
         u >>= zu;
 
-        GpuUInt128 currentV = v;
-        while (true)
+        do
         {
-            int zv = TrailingZeroCount(currentV);
-            currentV >>= zv;
-
-            bool swap = u > currentV;
-            GpuUInt128 min = ConditionalSelect(u, currentV, swap);
-            GpuUInt128 max = ConditionalSelect(currentV, u, swap);
-            max.Sub(min);
-
-            if (max.IsZero)
+            int zv = TrailingZeroCount(v);
+            v >>= zv;
+            if (u > v)
             {
-                return min << shift;
+                (u, v) = (v, u);
             }
 
-            u = min;
-            currentV = max;
+            v -= u;
         }
+        while (!v.IsZero);
+
+        return u << shift;
     }
 
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static GpuUInt128 ConditionalSelect(in GpuUInt128 left, in GpuUInt128 right, bool useRight)
-    {
-        ulong mask = useRight ? ulong.MaxValue : 0UL;
-        return new GpuUInt128(
-            left.High ^ ((left.High ^ right.High) & mask),
-            left.Low ^ ((left.Low ^ right.Low) & mask));
-    }
 
     public void Sub(ulong value)
     {
@@ -1550,15 +1529,6 @@ public struct GpuUInt128 : IComparable<GpuUInt128>, IEquatable<GpuUInt128>
         high = hi;
     }
 
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public void Pow2()
-    {
-        ulong operand = Low;
-        Low = operand * operand;
-        ulong highProduct = operand * High;
-        High = highProduct + MulHigh(operand, operand);
-    }
-
 }
 
 // TODO: Check if the TODO below is still relevant.

PerfectNumbers.Core/Gpu/GpuWorkLimiter.cs

@@ -6,14 +6,14 @@ public static class GpuWorkLimiter
     private static readonly object _lock = new();
     private static int _currentLimit = 1;
 
-    public static Lease Acquire()
+    public static IDisposable Acquire()
     {
-        // TODO: Replace the per-call Lease allocation with the pooled struct-based guard from the
+        // TODO: Replace the per-call Releaser allocation with the pooled struct-based guard from the
         // GpuLimiterThroughputBenchmarks so limiter acquisition does not allocate when we enter the
         // GPU scanning hot path.
         var sem = _semaphore;
         sem.Wait();
-        return new Lease(sem);
+        return new Releaser(sem);
     }
 
     public static void SetLimit(int value)
@@ -32,7 +32,7 @@ public static class GpuWorkLimiter
 
             // Swap to a new semaphore for the new limit. We intentionally
             // do not dispose the old semaphore to avoid releasing handles
-            // that may still be in use by existing Lease instances.
+            // that may still be in use by existing Releaser instances.
             // TODO: Consolidate with GpuPrimeWorkLimiter so both limiters share a pooled SemaphoreSlim and avoid rebuilding the
             // limiter state whenever limits are adjusted from the CLI.
             _semaphore = new SemaphoreSlim(value, value);
@@ -40,18 +40,25 @@ public static class GpuWorkLimiter
         }
     }
 
-    public sealed class Lease
+    private sealed class Releaser : IDisposable
     {
         private readonly SemaphoreSlim _sem;
+        private bool _disposed;
 
-        internal Lease(SemaphoreSlim sem)
+        public Releaser(SemaphoreSlim sem)
         {
             _sem = sem;
         }
 
         public void Dispose()
         {
+            if (_disposed)
+            {
+                return;
+            }
+
             _sem.Release();
+            _disposed = true;
         }
     }
 }

PerfectNumbers.Core/Gpu/KernelContainer.cs

@@ -1,58 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu;
-
-public sealed class KernelContainer
-{
-	// Serializes first-time initialization of kernels/buffers per accelerator.
-	public Action<AcceleratorStream, Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>? Order;
-
-	public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
-	ulong, ulong, ulong, ulong, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>>? Incremental;
-
-	public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
-		ResidueAutomatonArgs, ArrayView<ulong>, ArrayView1D<ulong, Stride1D.Dense>,
-		ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<uint, Stride1D.Dense>,
-		ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>? Pow2Mod;
-
-	public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
-			ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>? IncrementalOrder;
-
-	public Action<AcceleratorStream, Index1D, ulong, GpuUInt128, GpuUInt128, byte, ulong,
-		ResidueAutomatonArgs, ArrayView<int>, ArrayView1D<ulong, Stride1D.Dense>>? Pow2ModOrder;
-
-	public Kernel? SmallPrimeFactor;
-	
-	public Action<AcceleratorStream, Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>? SpecialMax;
-
-	// Optional device buffer with small divisor cycles (<= 4M). Index = divisor, value = cycle length.
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallCycles;
-
-	public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastOne;
-	public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastSeven;
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastOne;
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastSeven;
-
-	public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimeFactorsPrimes;
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimeFactorsSquares;
-
-	public void Dispose()
-	{
-		// Order = null;
-		// Incremental = null;
-		// Pow2Mod = null;
-		// IncrementalOrder = null;
-		// Pow2ModOrder = null;
-		// SmallPrimeFactor = null;
-		// SpecialMax = null;
-
-		// SmallCycles?.Dispose();
-		// SmallPrimesLastOne?.Dispose();
-		// SmallPrimesLastSeven?.Dispose();
-		// SmallPrimesPow2LastOne?.Dispose();
-		// SmallPrimesPow2LastSeven?.Dispose();
-		// SmallPrimeFactorsPrimes?.Dispose();
-		// SmallPrimeFactorsSquares?.Dispose();
-	}
-}

PerfectNumbers.Core/Gpu/KernelType.cs

@@ -1,14 +0,0 @@
-namespace PerfectNumbers.Core.Gpu;
-
-[Flags]
-public enum KernelType
-{
-	None,
-	SmallCycles,
-	SmallPrimes,
-	Pow2ModKernelScan,
-	OrderKernelScan,
-	IncrementalKernelScan,
-	IncrementalOrderKernelScan,
-	Pow2ModOrderKernelScan
-}

PerfectNumbers.Core/Gpu/Kernels/DivisorByDivisorKernels.cs

@@ -1,4 +1,7 @@
 using ILGPU;
+using ILGPU.Algorithms;
+using ILGPU.Runtime;
+using PerfectNumbers.Core;
 
 namespace PerfectNumbers.Core.Gpu;
 
@@ -50,28 +53,15 @@ internal static class DivisorByDivisorKernels
         int endIndex = offset + count;
         if (hasCycle)
         {
+            GpuUInt128 remainderValue = new(cycleRemainder);
             for (int exponentIndex = offset + 1; exponentIndex < endIndex; exponentIndex++)
             {
                 ulong exponent = exponents[exponentIndex];
                 ulong delta = exponent - previousExponent;
                 previousExponent = exponent;
 
-                if (delta >= cycleLength)
-                {
-                    delta -= cycleLength;
-                    if (delta >= cycleLength)
-                    {
-                        delta %= cycleLength;
-                    }
-                }
-
-                ulong nextRemainder = cycleRemainder + delta;
-                if (nextRemainder >= cycleLength)
-                {
-                    nextRemainder -= cycleLength;
-                }
-
-                cycleRemainder = nextRemainder;
+                remainderValue.AddMod(delta, cycleLength);
+                cycleRemainder = remainderValue.Low;
 
                 byte hit = 0;
                 if (cycleRemainder == 0UL)

PerfectNumbers.Core/Gpu/Kernels/DivisorKernels.cs

@@ -1,5 +1,6 @@
 using ILGPU;
 using ILGPU.Algorithms;
+using ILGPU.Runtime;
 
 namespace PerfectNumbers.Core.Gpu;
 

PerfectNumbers.Core/Gpu/Kernels/IncrementalKernels.cs

@@ -1,4 +1,5 @@
 using ILGPU;
+using ILGPU.Algorithms;
 using ILGPU.Runtime;
 
 namespace PerfectNumbers.Core.Gpu;

PerfectNumbers.Core/Gpu/Kernels/LucasLehmerKernels.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Runtime.CompilerServices;
 using ILGPU;
+using ILGPU.Runtime;
 using UInt128 = System.UInt128;
 
 namespace PerfectNumbers.Core.Gpu;
@@ -303,7 +305,7 @@ internal static class LucasLehmerKernels
         states[idx] = s;
     }
 
-    public static void Kernel(Index1D _, ulong exponent, GpuUInt128 modulus, ArrayView<GpuUInt128> state)
+    public static void Kernel(Index1D index, ulong exponent, GpuUInt128 modulus, ArrayView<GpuUInt128> state)
     {
         // Lucas–Lehmer iteration in the field GF(2^p-1).
         // For p < 128, use a Mersenne-specific squaring + reduction to avoid

PerfectNumbers.Core/Gpu/Kernels/NttBarrettKernels.cs

@@ -1,6 +1,5 @@
 using System.Runtime.CompilerServices;
 using ILGPU;
-using ILGPU.Runtime;
 
 namespace PerfectNumbers.Core.Gpu;
 
@@ -33,7 +32,7 @@ internal static class NttBarrettKernels
     }
 
     // Barrett-based squaring: v = v^2 mod n for 128-bit n
-    public static void SquareBarrett128Kernel(Index1D index, AcceleratorStream stream, ArrayView<GpuUInt128> data, ulong modHigh, ulong modLow, ulong muHigh, ulong muLow)
+    public static void SquareBarrett128Kernel(Index1D index, ArrayView<GpuUInt128> data, ulong modHigh, ulong modLow, ulong muHigh, ulong muLow)
     {
         var v = data[index];
         Mul128Full(v.High, v.Low, v.High, v.Low, out var z3, out var z2, out var z1, out var z0);

PerfectNumbers.Core/Gpu/Kernels/NttMontgomeryKernels.cs

@@ -1,6 +1,5 @@
 using System.Runtime.CompilerServices;
 using ILGPU;
-using ILGPU.Runtime;
 
 namespace PerfectNumbers.Core.Gpu;
 
@@ -44,7 +43,7 @@ internal static class NttMontgomeryKernels
         data[index] = new GpuUInt128(0UL, v);
     }
 
-    public static void SquareMont64Kernel(Index1D index, AcceleratorStream stream, ArrayView<GpuUInt128> data, ulong modulus, ulong nPrime)
+    public static void SquareMont64Kernel(Index1D index, ArrayView<GpuUInt128> data, ulong modulus, ulong nPrime)
     {
         ulong aR = data[index].Low;
         ulong v = MontMul64(aR, aR, modulus, nPrime);

PerfectNumbers.Core/Gpu/Kernels/OrderKernels.cs

@@ -1,4 +1,5 @@
 using ILGPU;
+using ILGPU.Runtime;
 
 namespace PerfectNumbers.Core.Gpu;
 

PerfectNumbers.Core/Gpu/Kernels/Pow2ModKernels.cs

@@ -1,4 +1,5 @@
 using ILGPU;
+using ILGPU.Algorithms;
 using ILGPU.Runtime;
 
 namespace PerfectNumbers.Core.Gpu;

PerfectNumbers.Core/Gpu/Kernels/Pow2MontgomeryKernels.cs

@@ -1,80 +1,26 @@
-using System.Runtime.CompilerServices;
 using ILGPU;
 using ILGPU.Runtime;
+using PerfectNumbers.Core;
 
-namespace PerfectNumbers.Core.Gpu.Kernels;
+namespace PerfectNumbers.Core.Gpu;
 
 internal static class Pow2MontgomeryKernels
 {
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static GpuUInt128 AdvancePolynomialGpu(GpuUInt128 x, ulong c, ulong modulus)
-	{
-		x.Pow2();
-		x.AddMod(c, modulus);
-		return x;
-	}
+    public static void Pow2MontgomeryKernelKeepMontgomery(
+        Index1D index,
+        ArrayView1D<ulong, Stride1D.Dense> exponents,
+        MontgomeryDivisorData divisor,
+        ArrayView1D<ulong, Stride1D.Dense> results)
+    {
+        results[index] = ULongExtensions.Pow2MontgomeryModWindowedGpuKeepMontgomery(divisor, exponents[index]);
+    }
 
-	public static void Pow2MontgomeryKernelKeepMontgomery(
-		Index1D index,
-		ArrayView1D<ulong, Stride1D.Dense> exponents,
-		MontgomeryDivisorData divisor,
-		ArrayView1D<ulong, Stride1D.Dense> results)
-	{
-		results[0] = ULongExtensions.Pow2MontgomeryModWindowedGpuKeepMontgomery(divisor, exponents[0]);
-	}
-
-	public static void Pow2MontgomeryKernelConvertToStandard(
-		Index1D index,
-		ArrayView1D<ulong, Stride1D.Dense> exponents,
-		MontgomeryDivisorData divisor,
-		ArrayView1D<ulong, Stride1D.Dense> results)
-	{
-		results[0] = ULongExtensions.Pow2MontgomeryModWindowedGpuConvertToStandard(divisor, exponents[0]);
-	}
-
-
-	public static void TryPollardRhoKernel(ulong n, int limit, ArrayView1D<ulong, Stride1D.Dense> randomState, ArrayView1D<byte, Stride1D.Dense> factored, ArrayView1D<ulong, Stride1D.Dense> factor)
-	{
-		factored[0] = 0;
-		if ((n & 1UL) == 0UL)
-		{
-			factor[0] = 2UL;
-			factored[0] = 1;
-			return;
-		}
-
-		int attempt = 0;
-		GpuUInt128 nGpuUInt128 = (GpuUInt128)n;
-		DeterministicRandomGpu random = new(randomState[0]);
-		while (attempt < limit)
-		{
-			ulong c = (random.NextUInt64() % (n - 1UL)) + 1UL;
-			GpuUInt128 x = (random.NextUInt64() % (n - 2UL)) + 2UL;
-			GpuUInt128 y = x;
-			GpuUInt128 d = GpuUInt128.One;
-
-			while (d.CompareTo(GpuUInt128.One) == 0)
-			{
-				x = AdvancePolynomialGpu(x, c, modulus: n);
-				y = AdvancePolynomialGpu(y, c, n);
-				y = AdvancePolynomialGpu(y, c, n);
-				GpuUInt128 diff = x.CompareTo(y) > 0 ? x - y : y - x;
-				d = GpuUInt128.BinaryGcd(diff, nGpuUInt128);
-			}
-
-			if (d != n)
-			{
-				if (d.High == 0)
-				{
-					factor[0] = d.Low;
-					factored[0] = 1;
-					return;
-				}
-			}
-
-			attempt++;
-		}
-
-		randomState[0] = random.State;
-	}
+    public static void Pow2MontgomeryKernelConvertToStandard(
+        Index1D index,
+        ArrayView1D<ulong, Stride1D.Dense> exponents,
+        MontgomeryDivisorData divisor,
+        ArrayView1D<ulong, Stride1D.Dense> results)
+    {
+        results[index] = ULongExtensions.Pow2MontgomeryModWindowedGpuConvertToStandard(divisor, exponents[index]);
+    }
 }

PerfectNumbers.Core/Gpu/Kernels/PrimeOrderSpecialMaxKernels.cs

@@ -1,79 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu;
-
-internal static partial class PrimeOrderGpuHeuristics
-{
-    internal static void EvaluateSpecialMaxCandidatesKernel(
-        Index1D index,
-        ulong phi,
-        ArrayView1D<ulong, Stride1D.Dense> factors,
-        int factorCount,
-        MontgomeryDivisorData divisor,
-        ArrayView1D<ulong, Stride1D.Dense> candidates,
-        ArrayView1D<ulong, Stride1D.Dense> resultOut)
-    {
-        if (index != 0)
-        {
-            return;
-        }
-
-        int actual = 0;
-        for (int i = 0; i < factorCount; i++)
-        {
-            ulong factor = factors[i];
-            if (factor <= 1UL)
-            {
-                continue;
-            }
-
-            ulong reduced = phi / factor;
-            if (reduced == 0UL)
-            {
-                continue;
-            }
-
-            candidates[actual] = reduced;
-            actual++;
-        }
-
-        if (actual == 0)
-        {
-            resultOut[0] = 1;
-            return;
-        }
-
-        for (int i = 1; i < actual; i++)
-        {
-            ulong current = candidates[i];
-            int insert = i - 1;
-            while (insert >= 0 && candidates[insert] > current)
-            {
-                candidates[insert + 1] = candidates[insert];
-                insert--;
-            }
-
-            candidates[insert + 1] = current;
-        }
-
-        var divisorPartial = new GpuDivisorPartialData(divisor.Modulus);
-        var stepper = new ExponentRemainderStepperGpu(divisorPartial);
-        if (stepper.InitializeIsUnityGpu(candidates[0]))
-        {
-			Atomic.Exchange(ref resultOut[0], 0);
-            return;
-        }
-
-        for (int i = 1; i < actual; i++)
-        {
-            if (stepper.ComputeNextIsUnityGpu(candidates[i]))
-            {
-				Atomic.Exchange(ref resultOut[0], 0);
-                return;
-            }
-        }
-
-        Atomic.Exchange(ref resultOut[0], 1);
-    }
-}

PerfectNumbers.Core/Gpu/Kernels/PrimeTesterKernels.cs

@@ -1,73 +1,33 @@
 using System.Runtime.CompilerServices;
 using ILGPU;
 using ILGPU.Algorithms;
-using ILGPU.Runtime;
-using PerfectNumbers.Core.Gpu.Accelerators;
 
 namespace PerfectNumbers.Core.Gpu;
 
-public enum HeuristicGpuDivisorTableKind : byte
-{
-    GroupA = 0,
-    GroupBEnding1 = 1,
-    GroupBEnding7 = 7,
-    GroupBEnding9 = 9,
-}
-
 internal static class PrimeTesterKernels
 {
     // GPU kernel: small-prime sieve only. Returns 1 if passes sieve (probable prime), 0 otherwise.
-    public static void SmallPrimeSieveKernel(
-		Index1D index,
-		ArrayView<ulong> numbers,
-		ArrayView<uint> smallPrimesLastOne,
-		ArrayView<uint> smallPrimesLastSeven,
-		ArrayView<uint> smallPrimesLastThree,
-		ArrayView<uint> smallPrimesLastNine,
-		ArrayView<ulong> smallPrimesPow2LastOne,
-		ArrayView<ulong> smallPrimesPow2LastSeven,
-		ArrayView<ulong> smallPrimesPow2LastThree,
-		ArrayView<ulong> smallPrimesPow2LastNine,
-		ArrayView<byte> results)
+    public static void SmallPrimeSieveKernel(Index1D index, ArrayView<ulong> numbers, ArrayView<uint> smallPrimes, ArrayView<byte> results)
     {
         ulong n = numbers[index];
         byte result = 1;
 
-        ArrayView<uint> primes;
-        ArrayView<ulong> primeSquares;
-        ulong lastDigit = n % 10UL;
-        switch (lastDigit)
-        {
-            case 1UL:
-                primes = smallPrimesLastOne;
-                primeSquares = smallPrimesPow2LastOne;
-                break;
-            case 3UL:
-                primes = smallPrimesLastThree;
-                primeSquares = smallPrimesPow2LastThree;
-                break;
-            case 7UL:
-                primes = smallPrimesLastSeven;
-                primeSquares = smallPrimesPow2LastSeven;
-                break;
-            case 9UL:
-                primes = smallPrimesLastNine;
-                primeSquares = smallPrimesPow2LastNine;
-				break;
-			default:
-				return;
-        }
+        // EvenPerfectBitScanner filters candidates so production GPU launches only see:
+        //  - n >= 31 (the scanner starts at 136,279,841 and test mode seeds 31)
+        //  - n odd (candidate generators and ModResidueTracker eliminate even exponents)
+        //  - n not divisible by 5 (residue prefiltering and AddPrimes transform cover these composites)
+        // Tests should honor the same constraints so the host wrapper can remain branchless.
 
-        int length = (int)primes.Length;
+        long length = smallPrimes.Length;
         for (int i = 0; i < length; i++)
         {
-            ulong primeSquare = primeSquares[i];
+            ulong prime = smallPrimes[i];
+            ulong primeSquare = (ulong)prime * prime;
             if (primeSquare > n)
             {
                 break;
             }
 
-            ulong prime = primes[i];
             if (n % prime == 0UL)
             {
                 result = 0;
@@ -78,69 +38,16 @@ internal static class PrimeTesterKernels
         results[index] = result;
     }
 
-    public static void HeuristicTrialCombinedDivisionKernel(
-        Index1D index,
-		byte nMod10,
-        ArrayView<int> resultFlag,
-        ulong n,
-        ulong maxDivisorSquare,
-        HeuristicCombinedGpuViews tables)
+    public static void HeuristicTrialDivisionKernel(Index1D index, ArrayView<ulong> divisors, ulong n, ArrayView<byte> results)
     {
-        // byte nMod10 = (byte)(n % 10UL);
-        ArrayView1D<ulong, Stride1D.Dense> divisors = tables.SelectDivisors(nMod10);
-        ArrayView1D<ulong, Stride1D.Dense> divisorSquares = tables.SelectDivisorSquares(nMod10);
-
-        int divisorLength = (int)divisorSquares.Length;
-        int threadIndex = index;
-        if (threadIndex >= divisorLength)
+        ulong divisor = divisors[index];
+        if (divisor <= 1UL)
         {
+            results[index] = 0;
             return;
         }
 
-        ulong divisorSquare = divisorSquares[threadIndex];
-        if (divisorSquare > maxDivisorSquare)
-        {
-            return;
-        }
-
-        ulong divisor = divisors[threadIndex];
-        divisor = n % divisor;
-        if (divisor == 0UL)
-        {
-            resultFlag[0] = 1;
-        }
-    }
-
-    public static void HeuristicTrialGroupABDivisionKernel(
-        Index1D index,
-        ArrayView<int> resultFlag,
-        ulong n,
-        ulong maxDivisorSquare,
-        HeuristicGpuDivisorTableKind tableKind,
-        HeuristicGroupABGpuViews tables)
-    {
-        ArrayView1D<ulong, Stride1D.Dense> divisors = tables.SelectDivisors(tableKind);
-        ArrayView1D<ulong, Stride1D.Dense> divisorSquares = tables.SelectDivisorSquares(tableKind);
-
-        int divisorLength = (int)divisorSquares.Length;
-        int threadIndex = index;
-        if (threadIndex >= divisorLength)
-        {
-            return;
-        }
-
-        ulong divisorSquare = divisorSquares[threadIndex];
-        if (divisorSquare > maxDivisorSquare)
-        {
-            return;
-        }
-
-        ulong divisor = divisors[threadIndex];
-        divisor = n % divisor;
-        if (divisor == 0UL)
-        {
-            resultFlag[0] = 1;
-        }
+        results[index] = n % divisor == 0UL ? (byte)1 : (byte)0;
     }
 
     public static void SharesFactorKernel(Index1D index, ArrayView<ulong> numbers, ArrayView<byte> results)
@@ -153,37 +60,35 @@ internal static class PrimeTesterKernels
 
     private static ulong BinaryGcdGpu(ulong u, ulong v)
     {
+        // TODO: Replace this inline GPU binary GCD with the kernel extracted from
+        // GpuUInt128BinaryGcdBenchmarks via GpuKernelPool so device callers reuse the
+        // fully unrolled ladder instead of this branchy fallback.
         bool uIsZero = u == 0UL;
         bool vIsZero = v == 0UL;
         bool eitherZero = uIsZero | vIsZero;
         ulong zeroResult = uIsZero ? v : u;
 
-        ulong combined = (u | v) | 1UL;
+        ulong combined = u | v | 1UL;
         int shift = XMath.TrailingZeroCount(combined);
-        ulong currentU = u >> XMath.TrailingZeroCount(u | 1UL);
-        ulong currentV = v >> XMath.TrailingZeroCount(v | 1UL);
 
-        while (true)
+        ulong normalizedU = u >> XMath.TrailingZeroCount(u | 1UL);
+        ulong normalizedV = v >> XMath.TrailingZeroCount(v | 1UL);
+
+        ulong currentU = normalizedU;
+        ulong currentV = normalizedV;
+        bool loopCondition = currentV != 0UL;
+
+        while (loopCondition)
         {
             currentV >>= XMath.TrailingZeroCount(currentV);
-            bool swap = currentU > currentV;
-            ulong minValue = ConditionalSelect(currentU, currentV, swap);
-            ulong maxValue = ConditionalSelect(currentV, currentU, swap);
-            currentV = maxValue - minValue;
+            ulong minValue = XMath.Min(currentU, currentV);
+            ulong maxValue = XMath.Max(currentU, currentV);
             currentU = minValue;
-            if (currentV == 0UL)
-            {
-                ulong gcd = currentU << shift;
-                return eitherZero ? zeroResult : gcd;
-            }
+            currentV = maxValue - minValue;
+            loopCondition = currentV != 0UL;
         }
-    }
 
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static ulong ConditionalSelect(ulong left, ulong right, bool useRight)
-    {
-        ulong mask = useRight ? ulong.MaxValue : 0UL;
-        return left ^ ((left ^ right) & mask);
+        ulong gcd = currentU << shift;
+        return eitherZero ? zeroResult : gcd;
     }
-
 }

PerfectNumbers.Core/Gpu/MersenneNumberDivisorGpuTester.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using ILGPU;
 using ILGPU.Runtime;
 
@@ -8,157 +9,127 @@ namespace PerfectNumbers.Core.Gpu;
 /// </summary>
 public sealed class MersenneNumberDivisorGpuTester
 {
-	[ThreadStatic]
-	private static Dictionary<Accelerator, Queue<MemoryBuffer1D<byte, Stride1D.Dense>>>? _resultBuffers;
+	private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>>> _kernelCache = new();
+	private readonly ConcurrentDictionary<Accelerator, MemoryBuffer1D<byte, Stride1D.Dense>> _resultBuffers = new();
 
-	private static Queue<MemoryBuffer1D<byte, Stride1D.Dense>> GetQueue(Accelerator accelerator)
-	{
-		var pool = _resultBuffers ??= [];
-		if (!pool.TryGetValue(accelerator, out var bufferQueue))
-		{
-			bufferQueue = [];
-			pool[accelerator] = bufferQueue;
-		}
+	private Action<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>> GetKernel(Accelerator accelerator) =>
+			_kernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>>(DivisorKernels.Kernel));
 
-		return bufferQueue;
-	}
+        public static void BuildDivisorCandidates()
+        {
+                ulong[] snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
+                (ulong divisor, uint cycle)[] list = new (ulong divisor, uint cycle)[snapshot.Length / 2];
+                ulong cycle;
+                int count = 0, i, snapshotLength = snapshot.Length;
+                for (i = 3; i < snapshotLength; i += 2)
+                {
+                        cycle = snapshot[i];
+                        if (cycle == 0U)
+                        {
+                                continue;
+                        }
 
-	private static Action<AcceleratorStream, Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>> GetDivisorKernel(Accelerator accelerator)
-	{
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>>(DivisorKernels.Kernel);
+                        list[count++] = ((ulong)i, (uint)cycle);
+                }
 
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>>>();
-	}
-
-	public static void BuildDivisorCandidates()
-	{
-		ulong[] snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
-		(ulong divisor, uint cycle)[] list = new (ulong divisor, uint cycle)[snapshot.Length / 2];
-		ulong cycle;
-		int count = 0, i, snapshotLength = snapshot.Length;
-		for (i = 3; i < snapshotLength; i += 2)
-		{
-			cycle = snapshot[i];
-			if (cycle == 0U)
-			{
-				continue;
-			}
-
-			list[count++] = ((ulong)i, (uint)cycle);
-		}
-
-		_divisorCandidates = count == 0 ? [] : list[..count];
-	}
-
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
-	public bool IsDivisible(ulong exponent, in ReadOnlyGpuUInt128 divisor)
-	{
-		// var accelerator = SharedGpuContext.CreateAccelerator();
-		var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		var accelerator = _accelerators[acceleratorIndex];
-		var stream = accelerator.CreateStream();
-		Queue<MemoryBuffer1D<byte, Stride1D.Dense>> resultBuffers = GetQueue(accelerator);
-		if (!resultBuffers.TryDequeue(out var resultBuffer))
-		{
-			// lock(accelerator)
-			{
-				resultBuffer = accelerator.Allocate1D<byte>(1);
-			}
-		}
+                _divisorCandidates = count == 0 ? [] : list[..count];
+        }
 
+    public bool IsDivisible(ulong exponent, in ReadOnlyGpuUInt128 divisor)
+    {
+        var gpu = GpuContextPool.RentPreferred(preferCpu: false);
+        var accelerator = gpu.Accelerator;
+        var kernel = GetKernel(accelerator);
+        var resultBuffer = _resultBuffers.GetOrAdd(accelerator, acc => acc.Allocate1D<byte>(1));
 		// There is no point in clearing this buffer. We always override item [0] and never use it beyond item [0]
-		// resultBuffer.MemSetToZero(stream);
-		var divisorKernel = GetDivisorKernel(accelerator);
-		divisorKernel(stream, 1, exponent, divisor, resultBuffer.View);
-		byte result = 0;
-		resultBuffer.View.CopyToCPU(stream, ref result, 1);
-		stream.Synchronize();
-		bool divisible = result != 0;
-		resultBuffers.Enqueue(resultBuffer);
-		stream.Dispose();
-		// AcceleratorPool.Shared.Return(accelerator);
-		// accelerator.Dispose();
-		return divisible;
-	}
+        // resultBuffer.MemSetToZero();
+        kernel(1, exponent, divisor, resultBuffer.View);
+        accelerator.Synchronize();
+        Span<byte> result = stackalloc byte[1];
+        resultBuffer.View.CopyToCPU(ref result[0], 1);
+        bool divisible = result[0] != 0;
+        result[0] = 0;
+        resultBuffer.View.CopyFromCPU(ref result[0], 1);
+        accelerator.Synchronize();
+        gpu.Dispose();
+        return divisible;
+    }
 
-	private static (ulong divisor, uint cycle)[]? _divisorCandidates = [];
+        private static (ulong divisor, uint cycle)[]? _divisorCandidates = Array.Empty<(ulong divisor, uint cycle)>();
 
-	public bool IsPrime(ulong p, UInt128 d, ulong divisorCyclesSearchLimit, out bool divisorsExhausted)
-	{
-		ReadOnlyGpuUInt128 readOnlyDivisor;
+    public bool IsPrime(ulong p, UInt128 d, ulong divisorCyclesSearchLimit, out bool divisorsExhausted)
+    {
+        ReadOnlyGpuUInt128 readOnlyDivisor;
 
-		if (d != UInt128.Zero)
-		{
-			readOnlyDivisor = new ReadOnlyGpuUInt128(d);
-			if (IsDivisible(p, in readOnlyDivisor))
-			{
-				divisorsExhausted = true;
-				return false;
-			}
+        if (d != UInt128.Zero)
+        {
+            readOnlyDivisor = new ReadOnlyGpuUInt128(d);
+            if (IsDivisible(p, in readOnlyDivisor))
+            {
+                divisorsExhausted = true;
+                return false;
+            }
 
-			divisorsExhausted = false;
-			return true;
-		}
+            divisorsExhausted = false;
+            return true;
+        }
 
-		if (_divisorCandidates is { Length: > 0 } candidates)
-		{
-			int candidateCount = candidates.Length;
-			for (int index = 0; index < candidateCount; index++)
-			{
-				(ulong candidateDivisor, uint cycle) = candidates[index];
-				if (p % cycle != 0UL)
-				{
-					continue;
-				}
+        if (_divisorCandidates is { Length: > 0 } candidates)
+        {
+            int candidateCount = candidates.Length;
+            for (int index = 0; index < candidateCount; index++)
+            {
+                (ulong candidateDivisor, uint cycle) = candidates[index];
+                if (p % cycle != 0UL)
+                {
+                    continue;
+                }
 
-				readOnlyDivisor = new ReadOnlyGpuUInt128(candidateDivisor); // Reusing readOnlyDivisor for candidate divisors.
-				if (IsDivisible(p, in readOnlyDivisor))
-				{
-					divisorsExhausted = true;
-					return false;
-				}
-			}
-		}
+                readOnlyDivisor = new ReadOnlyGpuUInt128(candidateDivisor); // Reusing readOnlyDivisor for candidate divisors.
+                if (IsDivisible(p, in readOnlyDivisor))
+                {
+                    divisorsExhausted = true;
+                    return false;
+                }
+            }
+        }
 
-		UInt128 kMul2;
-		var divisorCycles = MersenneDivisorCycles.Shared;
-		UInt128 maxK2 = UInt128.MaxValue / ((UInt128)p << 1);
-		ulong limit = divisorCyclesSearchLimit;
-		if ((UInt128)limit > maxK2)
-		{
-			limit = (ulong)maxK2;
-		}
+        UInt128 kMul2;
+        var divisorCycles = MersenneDivisorCycles.Shared;
+        UInt128 maxK2 = UInt128.MaxValue / ((UInt128)p << 1);
+        ulong limit = divisorCyclesSearchLimit;
+        if ((UInt128)limit > maxK2)
+        {
+            limit = (ulong)maxK2;
+        }
 
-		for (ulong k2 = 1UL; k2 <= limit; k2++)
-		{
-			kMul2 = (UInt128)k2 << 1;
-			UInt128 candidate = checked(kMul2 * p);
-			d = checked(candidate + UInt128.One);
-			if (p < 64UL && d == ((UInt128)1 << (int)p) - UInt128.One)
-			{
-				continue;
-			}
+        for (ulong k2 = 1UL; k2 <= limit; k2++)
+        {
+            kMul2 = (UInt128)k2 << 1;
+            UInt128 candidate = checked(kMul2 * p);
+            d = checked(candidate + UInt128.One);
+            if (p < 64UL && d == ((UInt128)1 << (int)p) - UInt128.One)
+            {
+                continue;
+            }
 
-			UInt128 cycle128 = MersenneDivisorCycles.GetCycle(d);
-			if ((UInt128)p % cycle128 != UInt128.Zero)
-			{
-				continue;
-			}
+            UInt128 cycle128 = MersenneDivisorCycles.GetCycle(d);
+            if ((UInt128)p % cycle128 != UInt128.Zero)
+            {
+                continue;
+            }
 
-			readOnlyDivisor = new ReadOnlyGpuUInt128(d); // Reusing readOnlyDivisor for generated divisors.
-			if (IsDivisible(p, in readOnlyDivisor))
-			{
-				divisorsExhausted = true;
-				return false;
-			}
-		}
+            readOnlyDivisor = new ReadOnlyGpuUInt128(d); // Reusing readOnlyDivisor for generated divisors.
+            if (IsDivisible(p, in readOnlyDivisor))
+            {
+                divisorsExhausted = true;
+                return false;
+            }
+        }
 
-		divisorsExhausted = (UInt128)divisorCyclesSearchLimit >= maxK2;
-		return true;
-	}
+        divisorsExhausted = (UInt128)divisorCyclesSearchLimit >= maxK2;
+        return true;
+    }
 
 }
 

PerfectNumbers.Core/Gpu/MersenneNumberIncrementalGpuTester.cs

@@ -12,122 +12,123 @@ public class MersenneNumberIncrementalGpuTester(GpuKernelType kernelType, bool u
     private readonly GpuKernelType _kernelType = kernelType;
     private readonly bool _useGpuOrder = useGpuOrder;
 
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
     public void Scan(ulong exponent, UInt128 twoP, LastDigit lastDigit, UInt128 maxK, ref bool isPrime)
     {
         throw new NotImplementedException($"GPU incremental scanning requires the device cycle heuristics implementation (kernel: {_kernelType}, GPU order: {_useGpuOrder}).");
 
-        // GpuPrimeWorkLimiter.Acquire();
-        var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		var accelerator = _accelerators[acceleratorIndex];
-        var stream = accelerator.CreateStream();
+        var gpuLease = GpuKernelPool.GetKernel(_useGpuOrder);
+        var execution = gpuLease.EnterExecutionScope();
+        var accelerator = gpuLease.Accelerator;
+        var stream = gpuLease.Stream;
         int batchSize = GpuConstants.ScanBatchSize; // large batch improves GPU occupancy
         UInt128 kStart = 1UL;
         ulong divMul = (ulong)((((UInt128)1 << 64) - UInt128.One) / exponent) + 1UL;
         byte last = lastDigit == LastDigit.Seven ? (byte)1 : (byte)0; // ILGPU kernels do not support bool parameters
 
-		KernelContainer kernels = GpuKernelPool.GetOrAddKernels(acceleratorIndex, stream, KernelType.Pow2ModKernelScan | KernelType.IncrementalKernelScan);
-		var pow2Kernel = kernels.Pow2Mod!;
-        var incKernel = kernels.Incremental!;
+        var pow2Kernel = gpuLease.Pow2ModKernel;
+        var incKernel = gpuLease.IncrementalKernel;
         ulong step10 = (exponent.Mod10() << 1).Mod10();
         ulong step8 = ((exponent & 7UL) << 1) & 7UL;
         ulong step3 = ((exponent % 3UL) << 1) % 3UL;
         ulong step5 = ((exponent % 5UL) << 1) % 5UL;
         GpuUInt128 twoPGpu = (GpuUInt128)twoP;
-        var smallCyclesView = GpuKernelPool.GetSmallCyclesOnDevice(kernels);
+        var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
         ResiduePrimeViews primeViews = default;
         if (_kernelType == GpuKernelType.Pow2Mod)
         {
-            primeViews = GpuKernelPool.GetSmallPrimesOnDevice(kernels);
+            primeViews = GpuKernelPool.EnsureSmallPrimesOnDevice(accelerator);
         }
 
         var orderBuffer = accelerator.Allocate1D<ulong>(batchSize);
-		// Avoid giant stack allocations that can trigger StackOverflow when batchSize is large.
-		// Rent a reusable array from the shared pool instead.
-		ArrayPool<ulong> ulongPool = ThreadStaticPools.UlongPool;
-		ulong[] orderArray = ulongPool.Rent(batchSize);
+        // Avoid giant stack allocations that can trigger StackOverflow when batchSize is large.
+        // Rent a reusable array from the shared pool instead.
+        ulong[] orderArray = ArrayPool<ulong>.Shared.Rent(batchSize);
         UInt128 remaining;
         int currentSize;
         int i;
         UInt128 q = UInt128.Zero;
-        while (kStart <= maxK && Volatile.Read(ref isPrime))
+        try
         {
-            remaining = maxK - kStart + UInt128.One;
-            currentSize = remaining > (UInt128)batchSize ? batchSize : (int)remaining;
-            Span<ulong> orders = orderArray.AsSpan(0, currentSize);
-            // Precompute residue automaton bases for this batch
-            UInt128 q0 = twoP * kStart + UInt128.One;
-            if (_kernelType == GpuKernelType.Pow2Mod)
+            while (kStart <= maxK && Volatile.Read(ref isPrime))
             {
-                q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
-                var kernelArgs = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
-                pow2Kernel(
-                    stream,
-                    currentSize,
-                    exponent,
-                    twoPGpu,
-                    (GpuUInt128)kStart,
-                    last,
-                    divMul,
-                    kernelArgs,
-                    orderBuffer.View,
-                    smallCyclesView,
-                    primeViews.LastOne,
-                    primeViews.LastSeven,
-                    primeViews.LastOnePow2,
-                    primeViews.LastSevenPow2);
-            }
-            else
-            {
-                q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
-                incKernel(
-                    stream,
-                    currentSize,
-                    exponent,
-                    twoPGpu,
-                    (GpuUInt128)kStart,
-                    last,
-                    divMul,
-                    q0m10,
-                    q0m8,
-                    q0m3,
-                    q0m5,
-                    orderBuffer.View,
-                    smallCyclesView);
-            }
-
-            orderBuffer.View.CopyToCPU(stream, ref MemoryMarshal.GetReference(orders), currentSize);
-            stream.Synchronize();
-            if (_kernelType == GpuKernelType.Pow2Mod)
-            {
-                for (i = 0; i < currentSize; i++)
+                remaining = maxK - kStart + UInt128.One;
+                currentSize = remaining > (UInt128)batchSize ? batchSize : (int)remaining;
+                Span<ulong> orders = orderArray.AsSpan(0, currentSize);
+                // Precompute residue automaton bases for this batch
+                UInt128 q0 = twoP * kStart + UInt128.One;
+                if (_kernelType == GpuKernelType.Pow2Mod)
                 {
-                    if (orders[i] != 0UL)
+                    q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
+                    var kernelArgs = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
+                    pow2Kernel(
+                        stream,
+                        currentSize,
+                        exponent,
+                        twoPGpu,
+                        (GpuUInt128)kStart,
+                        last,
+                        divMul,
+                        kernelArgs,
+                        orderBuffer.View,
+                        smallCyclesView,
+                        primeViews.LastOne,
+                        primeViews.LastSeven,
+                        primeViews.LastOnePow2,
+                        primeViews.LastSevenPow2);
+                }
+                else
+                {
+                    q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
+                    incKernel(
+                        stream,
+                        currentSize,
+                        exponent,
+                        twoPGpu,
+                        (GpuUInt128)kStart,
+                        last,
+                        divMul,
+                        q0m10,
+                        q0m8,
+                        q0m3,
+                        q0m5,
+                        orderBuffer.View,
+                        smallCyclesView);
+                }
+
+                stream.Synchronize();
+                orderBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(orders), currentSize);
+                if (_kernelType == GpuKernelType.Pow2Mod)
+                {
+                    for (i = 0; i < currentSize; i++)
                     {
-                        Volatile.Write(ref isPrime, false);
-                        break;
+                        if (orders[i] != 0UL)
+                        {
+                            Volatile.Write(ref isPrime, false);
+                            break;
+                        }
                     }
                 }
-            }
-            else
-            {
-                q = twoP * kStart + UInt128.One;
-                for (i = 0; i < currentSize && Volatile.Read(ref isPrime); i++, q += twoP)
+                else
                 {
-                    if (orders[i] != 0UL && q.IsPrimeCandidate())
+                    q = twoP * kStart + UInt128.One;
+                    for (i = 0; i < currentSize && Volatile.Read(ref isPrime); i++, q += twoP)
                     {
-                        Volatile.Write(ref isPrime, false);
+                        if (orders[i] != 0UL && q.IsPrimeCandidate())
+                        {
+                            Volatile.Write(ref isPrime, false);
+                        }
                     }
                 }
-            }
 
-            kStart += (UInt128)currentSize;
+                kStart += (UInt128)currentSize;
+            }
+        }
+        finally
+        {
+            ArrayPool<ulong>.Shared.Return(orderArray);
+            orderBuffer.Dispose();
+            execution.Dispose();
+            gpuLease.Dispose();
         }
-
-		stream.Dispose();
-        ulongPool.Return(orderArray);
-		orderBuffer.Dispose();
-        // GpuPrimeWorkLimiter.Release();
     }
 }

PerfectNumbers.Core/Gpu/MersenneNumberLucasLehmerGpuTester.cs

@@ -8,129 +8,46 @@ namespace PerfectNumbers.Core.Gpu;
 
 public class MersenneNumberLucasLehmerGpuTester
 {
-	[ThreadStatic]
-	private static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>>>? _lucasLehmerKernel;
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>>> KernelCache = new();
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ulong, ArrayView<GpuUInt128>>> AddSmallKernelCache = new();
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ulong, ArrayView<GpuUInt128>>> SubSmallKernelCache = new();
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ulong, ArrayView<GpuUInt128>>> ReduceKernelCache = new();
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ArrayView<GpuUInt128>, ArrayView<byte>>> IsZeroKernelCache = new();
+    private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>>> BatchKernelCache = new();
 
-	[ThreadStatic]
-	private static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>>>? _addSmallKernel;
+    private Action<Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>> GetKernel(Accelerator accelerator)
+    {
+        return KernelCache.GetOrAdd(accelerator, accel => accel.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>>(LucasLehmerKernels.Kernel));
+    }
 
-	[ThreadStatic]
-	private static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>>>? _subSmallKernel;
-	
-	[ThreadStatic]
-	private static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>>>? _reduceKernel;
+    private Action<Index1D, ulong, ArrayView<GpuUInt128>> GetAddSmallKernel(Accelerator accelerator) =>
+        AddSmallKernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView<GpuUInt128>>(LucasLehmerKernels.AddSmallKernel));
 
-	[ThreadStatic]
-    private static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ArrayView<GpuUInt128>, ArrayView<byte>>>? _isZeroKernel;
+    private Action<Index1D, ulong, ArrayView<GpuUInt128>> GetSubSmallKernel(Accelerator accelerator) =>
+        SubSmallKernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView<GpuUInt128>>(LucasLehmerKernels.SubtractSmallKernel));
 
-	[ThreadStatic]
-    private static Dictionary<Accelerator, Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>>>? _lucasLehmerBatchKernel;
+    private Action<Index1D, ulong, ArrayView<GpuUInt128>> GetReduceKernel(Accelerator accelerator) =>
+        ReduceKernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView<GpuUInt128>>(LucasLehmerKernels.ReduceModMersenneKernel));
 
-    private static Action<AcceleratorStream, Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>> GetLucasLehmerKernel(Accelerator accelerator)
-	{
-		var pool = _lucasLehmerKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
+    private Action<Index1D, ArrayView<GpuUInt128>, ArrayView<byte>> GetIsZeroKernel(Accelerator accelerator) =>
+        IsZeroKernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ArrayView<GpuUInt128>, ArrayView<byte>>(LucasLehmerKernels.IsZeroKernel));
 
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>>(LucasLehmerKernels.Kernel);
-
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		cached = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, GpuUInt128, ArrayView<GpuUInt128>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
-
-	private static Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>> GetAddSmallKernel(Accelerator accelerator)
-	{
-		var pool = _addSmallKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
-
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView<GpuUInt128>>(LucasLehmerKernels.AddSmallKernel);
-
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		cached = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
-
-	private static Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>> GetSubSmallKernel(Accelerator accelerator)
-	{
-		var pool = _subSmallKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
-
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView<GpuUInt128>>(LucasLehmerKernels.SubtractSmallKernel);
-
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		cached = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
-
-	private static Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>> GetReduceKernel(Accelerator accelerator)
-	{
-		var pool = _reduceKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
-
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView<GpuUInt128>>(LucasLehmerKernels.ReduceModMersenneKernel);
-
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		cached = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ArrayView<GpuUInt128>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
-
-	private static Action<AcceleratorStream, Index1D, ArrayView<GpuUInt128>, ArrayView<byte>> GetIsZeroKernel(Accelerator accelerator)
-	{
-		var pool = _isZeroKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
-
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<GpuUInt128>, ArrayView<byte>>(LucasLehmerKernels.IsZeroKernel);
-
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		cached = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<GpuUInt128>, ArrayView<byte>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
-
-	private static Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>> GetLucasLehmerBatchKernel(Accelerator accelerator)
-	{
-		var pool = _lucasLehmerBatchKernel ??= [];
-		if (pool.TryGetValue(accelerator, out var cached))
-		{
-			return cached;
-		}
-		
-		var loaded = accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>>(LucasLehmerKernels.KernelBatch);
-
-		var kernel = KernelUtil.GetKernel(loaded);
-
-		cached = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>>>();
-		pool[accelerator] = cached;
-		return cached;
-	}
+    private Action<Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>> GetBatchKernel(Accelerator accelerator) =>
+        BatchKernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<GpuUInt128>, ArrayView<GpuUInt128>>(LucasLehmerKernels.KernelBatch));
 
     // Configurable LL slice size to keep kernels short. Default 32.
     public int SliceSize = 32;
 
+    public bool IsMersennePrime(ulong exponent)
+    {
+        // Default to global kernel preference for backward compatibility.
+        bool runOnGpu = !GpuContextPool.ForceCpu;
+        // TODO: Inline this wrapper once callers request IsPrime directly so the Lucas–Lehmer fast path
+        // avoids an extra method frame; the LucasLehmerGpuBenchmarks showed the delegate hop shaving
+        // measurable time off tight reload loops when removed.
+        return IsPrime(exponent, runOnGpu);
+    }
+
     public bool IsPrime(ulong exponent, bool runOnGpu)
     {
         // Early rejections aligned with incremental/order sieves, but safe for small p:
@@ -147,11 +64,13 @@ public class MersenneNumberLucasLehmerGpuTester
             return false;
         }
 
+        var limiter = GpuPrimeWorkLimiter.Acquire();
         bool result;
         if (exponent >= 128UL)
         {
             if (!TryGetNttParameters(exponent, out var nttMod, out var primitiveRoot))
             {
+                limiter.Dispose();
                 throw new NotSupportedException("NTT parameters for the given exponent are not available.");
             }
 
@@ -159,22 +78,19 @@ public class MersenneNumberLucasLehmerGpuTester
         }
         else
         {
-        	// GpuPrimeWorkLimiter.Acquire();
-            var acceleratorIndex = AcceleratorPool.Shared.Rent();
-			var accelerator = _accelerators[acceleratorIndex];
-            var stream = accelerator.CreateStream();
+            var gpu = GpuContextPool.RentPreferred(preferCpu: !runOnGpu);
+            var accelerator = gpu.Accelerator;
+            var kernel = GetKernel(accelerator);
             var modulus = new GpuUInt128(((UInt128)1 << (int)exponent) - 1UL); // TODO: Cache these Mersenne moduli per exponent so LL GPU runs skip rebuilding them every launch.
-			var buffer = accelerator.Allocate1D<GpuUInt128>(1);
-			var lucasLehmerKernel = GetLucasLehmerKernel(accelerator);
-            lucasLehmerKernel(stream, 1, exponent, modulus, buffer.View);
-			stream.Synchronize();
-			// TODO: Replace this with .CopyToCPU with pre-allocated buffer using stream. Synchronize on the stream after copy.
+            var buffer = accelerator.Allocate1D<GpuUInt128>(1);
+            kernel(1, exponent, modulus, buffer.View);
+            accelerator.Synchronize();
             result = buffer.GetAsArray1D()[0].IsZero;
             buffer.Dispose();
-            stream.Dispose();
+            gpu.Dispose();
         }
 
-		// GpuPrimeWorkLimiter.Release();
+        limiter.Dispose();
         return result;
     }
 
@@ -194,18 +110,16 @@ public class MersenneNumberLucasLehmerGpuTester
             }
         }
 
-        var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		var accelerator = _accelerators[acceleratorIndex];
-        var stream = accelerator.CreateStream();
+        var gpu = GpuContextPool.RentPreferred(preferCpu: false);
+        var accelerator = gpu.Accelerator;
+        var kernel = GetBatchKernel(accelerator);
 
         var expBuffer = accelerator.Allocate1D<ulong>(count);
-		ArrayPool<ulong> ulongPool = ThreadStaticPools.UlongPool;
-		ulong[] expArray = ulongPool.Rent(count);
+        ulong[] expArray = ArrayPool<ulong>.Shared.Rent(count);
         exponents.CopyTo(expArray);
-        expBuffer.View.CopyFromCPU(stream, ref expArray[0], count);
+        expBuffer.View.CopyFromCPU(ref expArray[0], count);
 
-		ArrayPool<GpuUInt128> gpuUInt128Pool = ThreadStaticPools.GpuUInt128Pool;
-		GpuUInt128[] modulusArray = gpuUInt128Pool.Rent(count);
+        GpuUInt128[] modulusArray = ArrayPool<GpuUInt128>.Shared.Rent(count);
         for (int i = 0; i < count; i++)
         {
             // TODO: Replace this per-exponent shift with a small shared table (one entry per supported exponent < 128)
@@ -214,20 +128,19 @@ public class MersenneNumberLucasLehmerGpuTester
         }
 
         var modBuffer = accelerator.Allocate1D<GpuUInt128>(count);
-        modBuffer.View.CopyFromCPU(stream, ref modulusArray[0], count);
+        modBuffer.View.CopyFromCPU(ref modulusArray[0], count);
 
-		var stateBuffer = accelerator.Allocate1D<GpuUInt128>(count);
-		var lucasLehmerBatchKernel = GetLucasLehmerBatchKernel(accelerator);
-        lucasLehmerBatchKernel(stream, count, expBuffer.View, modBuffer.View, stateBuffer.View);
-        stateBuffer.View.CopyToCPU(stream, ref residues[0], count);
-        stream.Synchronize();
+        var stateBuffer = accelerator.Allocate1D<GpuUInt128>(count);
+        kernel(count, expBuffer.View, modBuffer.View, stateBuffer.View);
+        accelerator.Synchronize();
+        stateBuffer.View.CopyToCPU(ref residues[0], count);
 
         stateBuffer.Dispose();
         modBuffer.Dispose();
         expBuffer.Dispose();
-        gpuUInt128Pool.Return(modulusArray);
-        ulongPool.Return(expArray);
-        stream.Dispose();
+        ArrayPool<GpuUInt128>.Shared.Return(modulusArray);
+        ArrayPool<ulong>.Shared.Return(expArray);
+        gpu.Dispose();
     }
 
     public void IsMersennePrimeBatch(ReadOnlySpan<ulong> exponents, Span<bool> results)
@@ -238,27 +151,29 @@ public class MersenneNumberLucasLehmerGpuTester
             throw new ArgumentException("Result span too small", nameof(results));
         }
 
-		ArrayPool<GpuUInt128> gpuUInt128Pool = ThreadStaticPools.GpuUInt128Pool;
-		GpuUInt128[] buffer = gpuUInt128Pool.Rent(count);
-        ComputeResidues(exponents, buffer.AsSpan(0, count));
-        for (int i = 0; i < count; i++)
+        GpuUInt128[] buffer = ArrayPool<GpuUInt128>.Shared.Rent(count);
+        try
         {
-            results[i] = buffer[i].IsZero;
+            ComputeResidues(exponents, buffer.AsSpan(0, count));
+            for (int i = 0; i < count; i++)
+            {
+                results[i] = buffer[i].IsZero;
+            }
+        }
+        finally
+        {
+            ArrayPool<GpuUInt128>.Shared.Return(buffer);
         }
-        gpuUInt128Pool.Return(buffer);
     }
 
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
     private bool IsMersennePrimeNtt(ulong exponent, GpuUInt128 nttMod, GpuUInt128 primitiveRoot, bool runOnGpu)
     {
-        var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		var accelerator = _accelerators[acceleratorIndex];
-        var stream = accelerator.CreateStream();
-
+        var gpu = GpuContextPool.RentPreferred(preferCpu: !runOnGpu);
+        var accelerator = gpu.Accelerator;
+        var addKernel = GetAddSmallKernel(accelerator);
         var subKernel = GetSubSmallKernel(accelerator);
-		var reduceKernel = GetReduceKernel(accelerator);
-		var isZeroKernel = GetIsZeroKernel(accelerator);
+        var reduceKernel = GetReduceKernel(accelerator);
+        var zeroKernel = GetIsZeroKernel(accelerator);
 
         int limbCount = (int)((exponent + 127UL) / 128UL);
         int target = limbCount * 2;
@@ -268,9 +183,8 @@ public class MersenneNumberLucasLehmerGpuTester
             transformLength <<= 1;
         }
         var stateBuffer = accelerator.Allocate1D<GpuUInt128>(transformLength);
-		stateBuffer.MemSetToZero(stream);
-		var addSmallKernel = GetAddSmallKernel(accelerator);
-		addSmallKernel(stream, 1, 4UL, stateBuffer.View);
+        stateBuffer.MemSetToZero();
+        addKernel(1, 4UL, stateBuffer.View);
 
         // TODO(LL-SLICE): Slice Lucas–Lehmer iterations into short batches to
         // avoid long-running kernels and TDR. Example: process 8–64 iterations
@@ -285,26 +199,27 @@ public class MersenneNumberLucasLehmerGpuTester
             for (int s = 0; s < iter; s++)
             {
                 // Square in NTT domain with staged kernels (short runtime per kernel).
-                NttGpuMath.SquareDevice(accelerator, stream, stateBuffer.View, nttMod, primitiveRoot);
-                subKernel(stream, 1, 2UL, stateBuffer.View);
-                reduceKernel(stream, 1, exponent, stateBuffer.View);
+                NttGpuMath.SquareDevice(accelerator, stateBuffer.View, nttMod, primitiveRoot);
+                subKernel(1, 2UL, stateBuffer.View);
+                reduceKernel(1, exponent, stateBuffer.View);
             }
 
             // Synchronize between slices to yield to scheduler and avoid TDR.
+            accelerator.Synchronize();
             i += (ulong)iter;
         }
 
-        reduceKernel(stream, 1, exponent, stateBuffer.View);
-		var resultBuffer = accelerator.Allocate1D<byte>(1);
-        isZeroKernel(stream, 1, stateBuffer.View, resultBuffer.View);
-        Span<byte> result = stackalloc byte[1];
-        resultBuffer.View.CopyToCPU(stream, result);
-		stream.Synchronize();
-		
+        reduceKernel(1, exponent, stateBuffer.View);
+
+        var resultBuffer = accelerator.Allocate1D<byte>(1);
+        zeroKernel(1, stateBuffer.View, resultBuffer.View);
+        accelerator.Synchronize();
+        byte[] result = new byte[1];
+        resultBuffer.View.CopyToCPU(result);
         bool isPrime = result[0] != 0;
         resultBuffer.Dispose();
         stateBuffer.Dispose();
-        stream.Dispose();
+        gpu.Dispose();
         return isPrime;
     }
 
@@ -573,4 +488,6 @@ public class MersenneNumberLucasLehmerGpuTester
 
         return result;
     }
+
+
 }

PerfectNumbers.Core/Gpu/MersenneNumberOrderGpuTester.cs

@@ -7,73 +7,67 @@ public class MersenneNumberOrderGpuTester(GpuKernelType kernelType, bool useGpuO
 	private readonly GpuKernelType _kernelType = kernelType;
 	private readonly bool _useGpuOrder = useGpuOrder;
 
-	private static readonly Accelerator[] _accelerators = AcceleratorPool.Shared.Accelerators;
-
 	public void Scan(ulong exponent, UInt128 twoP, LastDigit lastDigit, UInt128 maxK, ref bool isPrime)
 	{
-		// GpuPrimeWorkLimiter.Acquire();
-		// var accelerator = SharedGpuContext.Accelerator;
-		var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		var accelerator = _accelerators[acceleratorIndex];
-		var stream = accelerator.CreateStream();
+		var gpuLease = GpuKernelPool.GetKernel(_useGpuOrder);
+		var execution = gpuLease.EnterExecutionScope();
+		var accelerator = gpuLease.Accelerator;
+		var stream = gpuLease.Stream;
 		int batchSize = GpuConstants.ScanBatchSize; // large batch improves GPU occupancy and avoids TDR
 		UInt128 kStart = UInt128.One;
 		ulong divMul = (ulong)((((UInt128)1 << 64) - UInt128.One) / exponent) + 1UL;
 		byte last = lastDigit == LastDigit.Seven ? (byte)1 : (byte)0; // ILGPU kernels do not support bool parameters
 
-		KernelContainer kernels = GpuKernelPool.GetOrAddKernels(acceleratorIndex, stream, KernelType.Pow2ModOrderKernelScan | KernelType.IncrementalOrderKernelScan);
-		var kernel = _kernelType switch
-		{
-			GpuKernelType.Pow2Mod => kernels.Pow2ModOrder!,
-			_ => kernels.IncrementalOrder!,
-		};
+                var kernel = _kernelType switch
+                {
+                        GpuKernelType.Pow2Mod => gpuLease.Pow2ModOrderKernel,
+                        _ => gpuLease.IncrementalOrderKernel,
+                };
 
-		MemoryBuffer1D<int, ILGPU.Stride1D.Dense>? foundBuffer;
-		// lock (accelerator)
-		{
-			foundBuffer = accelerator.Allocate1D<int>(1); // TODO: Replace this allocation with the pooled device buffer from GpuOrderKernelBenchmarks so repeated scans reuse the pinned staging memory instead of allocating per run.
-
-		}
-		exponent.Mod10_8_5_3Steps(out ulong step10, out ulong step8, out ulong step5, out ulong step3);
-
-		UInt128 remaining;
-		int currentSize;
-		int found = 0;
-
-		var smallCyclesView = GpuKernelPool.GetSmallCyclesOnDevice(kernels);
-		while (kStart <= maxK && Volatile.Read(ref isPrime))
-		{
-			remaining = maxK - kStart + 1UL;
-			currentSize = remaining > (UInt128)batchSize ? batchSize : (int)remaining;
-			// This clear is required because the result may not always be set. Remove it after the kernels are modified to always set the result.
-			foundBuffer.MemSetToZero(stream);
-			// Precompute residue automaton bases for this batch
-			UInt128 q0 = twoP * kStart + 1UL;
-			// TODO: Replace these modulo recomputations with the divisor-cycle stepping deltas captured in
-			// MersenneDivisorCycleLengthGpuBenchmarks so each batch advances via cached residues from the
-			// single snapshot block instead of recalculating mod 10/8/5/3 in every iteration.
-			q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
-			var kernelArgs = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
-
-			// Ensure device has small cycles table for early rejections in order kernels
-			kernel(
-				stream, currentSize, exponent, (GpuUInt128)twoP, (GpuUInt128)kStart,
-				last, divMul, kernelArgs, foundBuffer.View, smallCyclesView
-			);
-
-			foundBuffer.View.CopyToCPU(stream, ref found, 1);
-			stream.Synchronize();
-			if (found != 0)
+                var foundBuffer = accelerator.Allocate1D<int>(1); // TODO: Replace this allocation with the pooled device buffer from GpuOrderKernelBenchmarks so repeated scans reuse the pinned staging memory instead of allocating per run.
+                exponent.Mod10_8_5_3Steps(out ulong step10, out ulong step8, out ulong step5, out ulong step3);
+                try
+                {
+			UInt128 remaining;
+			int currentSize;
+			int found = 0;
+			while (kStart <= maxK && Volatile.Read(ref isPrime))
 			{
-				Volatile.Write(ref isPrime, false);
-				break;
-			}
+				remaining = maxK - kStart + 1UL;
+				currentSize = remaining > (UInt128)batchSize ? batchSize : (int)remaining;
+				// This clear is required because the result may not always be set. Remove it after the kernels are modified to always set the result.
+				foundBuffer.MemSetToZero();
+				// Precompute residue automaton bases for this batch
+                                UInt128 q0 = twoP * kStart + 1UL;
+                                // TODO: Replace these modulo recomputations with the divisor-cycle stepping deltas captured in
+                                // MersenneDivisorCycleLengthGpuBenchmarks so each batch advances via cached residues from the
+                                // single snapshot block instead of recalculating mod 10/8/5/3 in every iteration.
+                                q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
+                                var kernelArgs = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
 
-			kStart += (UInt128)currentSize;
+
+				// Ensure device has small cycles table for early rejections in order kernels
+				var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
+				kernel(stream, currentSize, exponent, (GpuUInt128)twoP, (GpuUInt128)kStart, last, divMul,
+						kernelArgs, foundBuffer.View, smallCyclesView);
+
+				stream.Synchronize();
+				foundBuffer.View.CopyToCPU(ref found, 1);
+				if (found != 0)
+				{
+					Volatile.Write(ref isPrime, false);
+					break;
+				}
+
+				kStart += (UInt128)currentSize;
+			}
+		}
+		finally
+		{
+			foundBuffer.Dispose();
+			execution.Dispose();
+			gpuLease.Dispose();
 		}
 
-		stream.Dispose();
-		foundBuffer.Dispose();
-		// GpuPrimeWorkLimiter.Release();
 	}
 }