Split GPU heuristic tables by scope

EvenPerfectBitScanner.Benchmarks/PrimeTesterBenchmarks.cs

@@ -1,3 +1,6 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using Open.Numeric.Primes;
@@ -9,6 +12,7 @@ namespace EvenPerfectBitScanner.Benchmarks;
 [MemoryDiagnoser]
 public class PrimeTesterBenchmarks
 {
+    private static readonly HeuristicCombinedPrimeTester _heuristicCombinedTester = new();
     private static readonly HeuristicPrimeTester _heuristicTester = new();
     private ulong[] _candidates = [];
 
@@ -30,7 +34,7 @@ public class PrimeTesterBenchmarks
         _ = Prime.Numbers.IsPrime(_candidates[0]);
     }
 
-    [Benchmark]
+    [Benchmark(Baseline = true)]
     public int HeuristicCpu()
     {
         HeuristicPrimeTester tester = _heuristicTester;
@@ -100,15 +104,18 @@ public class PrimeTesterBenchmarks
         return primeCount;
     }
 
+	private static readonly PrimeTester _nonHeuristicTester = new();
+
     [Benchmark]
     public int NonHeuristicGpu()
 	{
+		PrimeTester tester = _nonHeuristicTester;
         ulong[] values = _candidates;
         int primeCount = 0;
 
         for (int i = 0; i < values.Length; i++)
         {
-            if (PrimeTester.IsPrimeGpu(values[i]))
+            if (tester.IsPrimeGpu(values[i]))
             {
                 primeCount++;
             }
@@ -117,7 +124,7 @@ public class PrimeTesterBenchmarks
         return primeCount;
     }
 
-    [Benchmark(Baseline = true)]
+    [Benchmark]
     public int NonHeuristicCpu()
     {
         ulong[] values = _candidates;

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;
@@ -58,15 +58,14 @@ internal static class Program
 			bool startPrimeProvided = _cliArguments.StartPrimeProvided;
 			int threadCount = Math.Max(1, _cliArguments.ThreadCount);
 			int gpuPrimeBatch = Math.Max(1, _cliArguments.GpuPrimeBatch);
-			int gpuPrimeThreads = Math.Max(1, _cliArguments.GpuPrimeThreads);
 			UnboundedTaskScheduler.ConfigureThreadCount(threadCount);
 			PrimeTester.GpuBatchSize = gpuPrimeBatch;
-			GpuPrimeWorkLimiter.SetLimit(gpuPrimeThreads);
 			GpuContextPool.WarmUpPool(threadCount);
-			PrimeTester.WarmUpGpuKernels(gpuPrimeThreads);
+			PrimeTester.WarmUpGpuKernels(threadCount);
 			Console.WriteLine("Starting up threads...");
 			_ = UnboundedTaskScheduler.Instance;
 			int blockSize = Math.Max(1, _cliArguments.BlockSize);
+			int gpuPrimeThreads = Math.Max(1, _cliArguments.GpuPrimeThreads);
 			GpuKernelType kernelType = _cliArguments.KernelType;
 			bool useBitTransform = _cliArguments.UseBitTransform;
 			bool useOrder = _cliArguments.UseOrder;
@@ -118,6 +117,9 @@ internal static class Program
 				return;
 			}
 
+			// Apply GPU prime sieve runtime configuration
+			GpuPrimeWorkLimiter.SetLimit(gpuPrimeThreads);
+			PrimeTester.GpuBatchSize = gpuPrimeBatch;
 
 			MersenneDivisorCycles mersenneDivisorCycles = new();
 			if (!File.Exists(cyclesPath) || continueCyclesGeneration)
@@ -176,7 +178,7 @@ internal static class Program
 			blockSize = useByDivisor ? 1 : blockSize;
 
 			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)
@@ -626,7 +628,7 @@ internal static class Program
 		{
 			if (!(_runPrimesOnCpu
 					? PrimeTester.IsPrime(p)
-					: PrimeTester.IsPrimeGpu(p)))
+					: PrimeTesters.Value!.IsPrimeGpu(p)))
 			{
 				_lastCompositeP = true;
 				return false;

PerfectNumbers.Core.Tests/Gpu/GpuPrimeLimiterTests.cs

@@ -18,19 +18,19 @@ public class GpuPrimeLimiterTests
         var startedSecond = new TaskCompletionSource<bool>();
         var sw = new Stopwatch();
 
-        GpuPrimeWorkLimiter.Acquire();
+        var first = GpuPrimeWorkLimiter.Acquire();
         sw.Start();
 
         var secondTask = Task.Run(() =>
         {
-            GpuPrimeWorkLimiter.Acquire();
+            var second = GpuPrimeWorkLimiter.Acquire();
             try
             {
                 startedSecond.TrySetResult(true);
             }
             finally
             {
-				GpuPrimeWorkLimiter.Release();
+                second.Dispose();
             }
         });
 
@@ -43,7 +43,7 @@ public class GpuPrimeLimiterTests
         finally
         {
             // Release first after the initial wait so the second task can proceed.
-			GpuPrimeWorkLimiter.Release();
+            first.Dispose();
         }
 
         await secondTask.WaitAsync(TimeSpan.FromSeconds(1));

PerfectNumbers.Core.Tests/Gpu/PrimeTesterGpuTests.cs

@@ -16,7 +16,7 @@ public class PrimeTesterGpuTests
             ulong[] primes = [31UL, 61UL, 89UL, 107UL, 127UL, 521UL];
             foreach (ulong prime in primes)
             {
-				PrimeTester.IsPrimeGpu(prime).Should().BeTrue();
+                tester.IsPrimeGpu(prime).Should().BeTrue();
             }
         }
         finally
@@ -34,7 +34,7 @@ public class PrimeTesterGpuTests
             ulong[] composites = [33UL, 39UL, 51UL, 77UL, 91UL];
             foreach (ulong composite in composites)
             {
-				PrimeTester.IsPrimeGpu(composite).Should().BeFalse();
+                tester.IsPrimeGpu(composite).Should().BeFalse();
             }
         }
         finally

PerfectNumbers.Core.Tests/PrimeTester/PrimeTesterIsPrimeTests.cs

@@ -39,7 +39,7 @@ public class PrimeTesterIsPrimeTests
     {
         var tester = new PrimeTester();
 
-		PrimeTester.IsPrimeGpu(n).Should().Be(expected);
+        tester.IsPrimeGpu(n).Should().Be(expected);
     }
 
     [Fact]
@@ -64,7 +64,7 @@ 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]);
         });
 
         results.Should().AllBeEquivalentTo(true);
@@ -73,7 +73,7 @@ public class PrimeTesterIsPrimeTests
         {
             foreach (ulong prime in primes)
             {
-				PrimeTester.IsPrimeGpu(prime).Should().BeTrue();
+                testers.Value!.IsPrimeGpu(prime).Should().BeTrue();
             }
         });
     }

PerfectNumbers.Core/Gpu/DivisorGeneratorGpuCache.cs

@@ -0,0 +1,142 @@
+using System;
+using System.Collections.Concurrent;
+using System.Runtime.CompilerServices;
+using ILGPU;
+using ILGPU.Runtime;
+
+namespace PerfectNumbers.Core.Gpu;
+
+internal static class DivisorGeneratorGpuCache
+{
+        private sealed class AcceleratorReferenceComparer : IEqualityComparer<Accelerator>
+        {
+                public static AcceleratorReferenceComparer Instance { get; } = new();
+
+                public bool Equals(Accelerator? x, Accelerator? y)
+                {
+                        return ReferenceEquals(x, y);
+                }
+
+                public int GetHashCode(Accelerator obj)
+                {
+                        return RuntimeHelpers.GetHashCode(obj);
+                }
+        }
+
+        private sealed class DivisorGeneratorGpuTables : IDisposable
+        {
+                internal DivisorGeneratorGpuTables(Accelerator accelerator)
+                {
+                        SmallPrimes = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimes);
+                        SmallPrimesPow2 = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2);
+                        SmallPrimesLastOne = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastOne);
+                        SmallPrimesPow2LastOne = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastOne);
+                        SmallPrimesLastSeven = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastSeven);
+                        SmallPrimesPow2LastSeven = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastSeven);
+                        SmallPrimesLastThree = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastThree);
+                        SmallPrimesPow2LastThree = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastThree);
+                        SmallPrimesLastNine = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastNine);
+                        SmallPrimesPow2LastNine = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastNine);
+                        SmallPrimesLastOneWithoutLastThree = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastOneWithoutLastThree);
+                        SmallPrimesPow2LastOneWithoutLastThree = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastOneWithoutLastThree);
+                        SmallPrimesLastSevenWithoutLastThree = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastSevenWithoutLastThree);
+                        SmallPrimesPow2LastSevenWithoutLastThree = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastSevenWithoutLastThree);
+                        SmallPrimesLastNineWithoutLastThree = AllocateAndCopyUInt(accelerator, DivisorGenerator.SmallPrimesLastNineWithoutLastThree);
+                        SmallPrimesPow2LastNineWithoutLastThree = AllocateAndCopyULong(accelerator, DivisorGenerator.SmallPrimesPow2LastNineWithoutLastThree);
+                }
+
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimes { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2 { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastOne { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastOne { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastSeven { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastSeven { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastThree { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastThree { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastNine { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastNine { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastOneWithoutLastThree { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastOneWithoutLastThree { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastSevenWithoutLastThree { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastSevenWithoutLastThree { get; }
+                internal MemoryBuffer1D<uint, Stride1D.Dense> SmallPrimesLastNineWithoutLastThree { get; }
+                internal MemoryBuffer1D<ulong, Stride1D.Dense> SmallPrimesPow2LastNineWithoutLastThree { get; }
+
+                public void Dispose()
+                {
+                        SmallPrimes.Dispose();
+                        SmallPrimesPow2.Dispose();
+                        SmallPrimesLastOne.Dispose();
+                        SmallPrimesPow2LastOne.Dispose();
+                        SmallPrimesLastSeven.Dispose();
+                        SmallPrimesPow2LastSeven.Dispose();
+                        SmallPrimesLastThree.Dispose();
+                        SmallPrimesPow2LastThree.Dispose();
+                        SmallPrimesLastNine.Dispose();
+                        SmallPrimesPow2LastNine.Dispose();
+                        SmallPrimesLastOneWithoutLastThree.Dispose();
+                        SmallPrimesPow2LastOneWithoutLastThree.Dispose();
+                        SmallPrimesLastSevenWithoutLastThree.Dispose();
+                        SmallPrimesPow2LastSevenWithoutLastThree.Dispose();
+                        SmallPrimesLastNineWithoutLastThree.Dispose();
+                        SmallPrimesPow2LastNineWithoutLastThree.Dispose();
+                }
+
+                private static MemoryBuffer1D<uint, Stride1D.Dense> AllocateAndCopyUInt(Accelerator accelerator, uint[] source)
+                {
+                        var buffer = accelerator.Allocate1D<uint>(source.Length);
+                        if (source.Length > 0)
+                        {
+                                buffer.View.CopyFromCPU(source);
+                        }
+
+                        return buffer;
+                }
+
+                private static MemoryBuffer1D<ulong, Stride1D.Dense> AllocateAndCopyULong(Accelerator accelerator, ulong[] source)
+                {
+                        var buffer = accelerator.Allocate1D<ulong>(source.Length);
+                        if (source.Length > 0)
+                        {
+                                buffer.View.CopyFromCPU(source);
+                        }
+
+                        return buffer;
+                }
+        }
+
+        private static readonly ConcurrentDictionary<Accelerator, DivisorGeneratorGpuTables> Cache = new(AcceleratorReferenceComparer.Instance);
+
+        public static void WarmUpByDivisorTables(Accelerator accelerator)
+        {
+                if (accelerator is null || accelerator.AcceleratorType == AcceleratorType.CPU)
+                {
+                        return;
+                }
+
+                Cache.GetOrAdd(accelerator, acc => new DivisorGeneratorGpuTables(acc));
+        }
+
+        public static void Clear(Accelerator accelerator)
+        {
+                if (accelerator is null)
+                {
+                        return;
+                }
+
+                if (Cache.TryRemove(accelerator, out var tables))
+                {
+                        tables.Dispose();
+                }
+        }
+
+        public static void DisposeAll()
+        {
+                foreach (var entry in Cache)
+                {
+                        entry.Value.Dispose();
+                }
+
+                Cache.Clear();
+        }
+}

PerfectNumbers.Core/Gpu/GpuContextPool.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Concurrent;
 using ILGPU;
 using ILGPU.Runtime;
@@ -11,15 +12,14 @@ public static class GpuContextPool
 	// Default device preference for generic GPU kernels (prime scans, NTT, etc.)
 	internal sealed class PooledContext
 	{
-		public readonly Context Context;
-		public readonly Accelerator Accelerator;
+		public Context Context { get; }
+		public Accelerator Accelerator { get; }
 
-		public PooledContext(KernelContainer kernels)
+		public PooledContext()
 		{
-			Context = SharedGpuContext.Context;
-			Accelerator = SharedGpuContext.Accelerator;
-			GpuStaticTableInitializer.EnsureStaticTables(kernels, Accelerator);
-			kernels.Dispose();
+			Context = Context.CreateDefault();
+			Accelerator = Context.GetPreferredDevice(false).CreateAccelerator(Context);
+			DivisorGeneratorGpuCache.WarmUpByDivisorTables(Accelerator);
 			// 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
@@ -33,11 +33,11 @@ public static class GpuContextPool
 			// Release PrimeTester GPU state for this accelerator (kernel/device primes)
 			// Clear any per-accelerator cached resources to avoid releasing
 			// after the accelerator is destroyed.
+			DivisorGeneratorGpuCache.Clear(Accelerator);
 			PrimeTester.ClearGpuCaches(Accelerator);
 
-			// These resources are shared between GPU leases
-			//  Accelerator.Dispose();
-			// 	Context.Dispose();
+			Accelerator.Dispose();
+			Context.Dispose();
 		}
 	}
 
@@ -53,10 +53,9 @@ public static class GpuContextPool
 		}
 
 		// Create a new accelerator when the pool does not have one available.
-		return new GpuContextLease(new PooledContext(GpuKernelPool.GetKernels()));
+		return new GpuContextLease(new PooledContext());
 	}
 
-
 	public static void WarmUpPool(int threadCount)
 	{
 		if (threadCount <= WarmedGpuContextCount)
@@ -65,16 +64,15 @@ public static class GpuContextPool
 		}
 
 		int toCreate = threadCount - WarmedGpuContextCount;
-		Console.WriteLine($"Warming up GPU context pool to {toCreate} contexts...");
 		var contexts = new PooledContext[toCreate];
-		var pool = GpuPool;
-		PooledContext context;
 		for (int i = 0; i < toCreate; i++)
 		{
-			KernelContainer kernels = GpuKernelPool.GetKernels();
-			context = new PooledContext(kernels);
-			contexts[i] = context;
-			pool.Enqueue(context);
+			contexts[i] = new PooledContext();
+		}
+
+		for (int i = 0; i < toCreate; i++)
+		{
+			GpuPool.Enqueue(contexts[i]);
 		}
 
 		WarmedGpuContextCount = threadCount;
@@ -87,6 +85,7 @@ public static class GpuContextPool
 			gpu.Dispose();
 		}
 
+		DivisorGeneratorGpuCache.DisposeAll();
 		PrimeTester.DisposeGpuContexts();
 		WarmedGpuContextCount = 0;
 	}
@@ -97,30 +96,21 @@ public static class GpuContextPool
 		GpuPool.Enqueue(ctx);
 	}
 
-	public struct GpuContextLease
+	public readonly struct GpuContextLease
 	{
-		private PooledContext? _ctx;
-		private bool _disposed;
+		private readonly PooledContext _ctx;
 
 		internal GpuContextLease(PooledContext ctx)
 		{
 			_ctx = ctx;
-			_disposed = false;
 		}
 
-		public Context Context => _ctx!.Context;
-		public Accelerator Accelerator => _ctx!.Accelerator;
+		public readonly Context Context => _ctx.Context;
+		public readonly Accelerator Accelerator => _ctx.Accelerator;
 
-		public void Dispose()
+		public readonly void Dispose()
 		{
-			if (_disposed)
-			{
-				return;
-			}
-
-			_disposed = true;
-			Return(_ctx!);
-			_ctx = null;
+			Return(_ctx);
 		}
 	}
 }

PerfectNumbers.Core/Gpu/GpuKernelLease.cs

@@ -2,7 +2,6 @@ using System;
 using System.Collections.Concurrent;
 using ILGPU;
 using ILGPU.Runtime;
-using PerfectNumbers.Core;
 using static PerfectNumbers.Core.Gpu.GpuContextPool;
 
 namespace PerfectNumbers.Core.Gpu;
@@ -11,24 +10,25 @@ public sealed class GpuKernelLease
 {
     private static readonly ConcurrentQueue<GpuKernelLease> Pool = new();
 
+    private Action? _releaseLimiter;
     private GpuContextLease? _gpu;
-    public KernelContainer Kernels;
+    private KernelContainer? _kernels;
     private AcceleratorStream? _stream;
 
-    private GpuKernelLease(KernelContainer kernels)
-	{
-		Kernels = kernels;
-	}
+    private GpuKernelLease()
+    {
+    }
 
-    internal static GpuKernelLease Rent(GpuContextLease gpu, KernelContainer kernels)
+    internal static GpuKernelLease Rent(GpuPrimeWorkLimiter.Lease limiter, GpuContextLease gpu, KernelContainer kernels)
     {
         if (!Pool.TryDequeue(out var lease))
         {
-            lease = new GpuKernelLease(kernels);
+            lease = new GpuKernelLease();
         }
 
+        lease._releaseLimiter = limiter.Dispose;
         lease._gpu = gpu;
-        lease.Kernels = kernels;
+        lease._kernels = kernels;
         lease._stream = null;
         return lease;
     }
@@ -56,7 +56,7 @@ public sealed class GpuKernelLease
         get
         {
             var accel = Accelerator; // avoid capturing 'this' in lambda
-            return KernelContainer.InitOnce(ref Kernels!.Order, () =>
+            return KernelContainer.InitOnce(ref _kernels!.Order, () =>
             {
                 var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, ulong, ArrayView<GpuUInt128>, ArrayView<ulong>>(OrderKernels.OrderKernelScan);
                 var kernel = KernelUtil.GetKernel(loaded);
@@ -70,7 +70,7 @@ public sealed class GpuKernelLease
         get
         {
             var accel = Accelerator;
-            return KernelContainer.InitOnce(ref Kernels!.Pow2Mod, () =>
+            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);
@@ -84,7 +84,7 @@ public sealed class GpuKernelLease
         get
         {
             var accel = Accelerator;
-            return KernelContainer.InitOnce(ref Kernels!.Incremental, () =>
+            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);
@@ -98,7 +98,7 @@ public sealed class GpuKernelLease
         get
         {
             var accel = Accelerator;
-            return KernelContainer.InitOnce(ref Kernels!.IncrementalOrder, () =>
+            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);
@@ -112,7 +112,7 @@ public sealed class GpuKernelLease
         get
         {
             var accel = Accelerator;
-            return KernelContainer.InitOnce(ref Kernels!.Pow2ModOrder, () =>
+            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);
@@ -121,26 +121,12 @@ public sealed class GpuKernelLease
         }
     }
 
-    public Action<AcceleratorStream, Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ushort, Stride1D.Dense>> SpecialMaxKernel
-    {
-        get
-        {
-            var accel = Accelerator;
-            return KernelContainer.InitOnce(ref Kernels!.SpecialMax, () =>
-            {
-                var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ushort, Stride1D.Dense>>(PrimeOrderGpuHeuristics.EvaluateSpecialMaxCandidatesKernel);
-                var kernel = KernelUtil.GetKernel(loaded);
-                return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ushort, 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;
-            return KernelContainer.InitOnce(ref Kernels!.SmallPrimeFactor, () =>
+            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);
@@ -157,8 +143,10 @@ public sealed class GpuKernelLease
         _gpu?.Dispose();
         _gpu = null;
 
-		Kernels?.Dispose();
-		GpuPrimeWorkLimiter.Release();
+        _releaseLimiter?.Invoke();
+        _releaseLimiter = null;
+
+        _kernels = null;
         Pool.Enqueue(this);
     }
 

PerfectNumbers.Core/Gpu/GpuKernelPool.cs

@@ -1,4 +1,3 @@
-using PerfectNumbers.Core;
 using System.Collections.Concurrent;
 using ILGPU;
 using ILGPU.Runtime;
@@ -8,315 +7,297 @@ 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 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 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;
-	public Action<AcceleratorStream, Index1D, ulong, ArrayView1D<ulong, Stride1D.Dense>, int, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ushort, Stride1D.Dense>>? SpecialMax;
+    // 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<ulong, Stride1D.Dense>? SpecialMaxFactors;
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SpecialMaxCandidates;
-	public MemoryBuffer1D<ushort, Stride1D.Dense>? SpecialMaxResult;
-	public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastOne;
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastOne;
-	public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastSeven;
-	public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastSeven;
+    // 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;
-		}
+    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 void Dispose() => GpuKernelPool.Return(this);
+        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)
+    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 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(
-	MemoryBuffer1D<uint, Stride1D.Dense> primes,
-	MemoryBuffer1D<ulong, Stride1D.Dense> squares,
-	int count)
+public readonly struct SmallPrimeFactorTables
 {
-	public readonly MemoryBuffer1D<uint, Stride1D.Dense> Primes = primes;
-	public readonly MemoryBuffer1D<ulong, Stride1D.Dense> Squares = squares;
-	public readonly int Count = count;
+    public readonly MemoryBuffer1D<uint, Stride1D.Dense> Primes;
+    public readonly MemoryBuffer1D<ulong, Stride1D.Dense> Squares;
+    public readonly int Count;
 
-	public ArrayView1D<uint, Stride1D.Dense> PrimesView => Primes.View;
-	public ArrayView1D<ulong, Stride1D.Dense> SquaresView => Squares.View;
+    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(
-		MemoryBuffer1D<ulong, Stride1D.Dense> primeSlots,
-		MemoryBuffer1D<int, Stride1D.Dense> exponentSlots,
-		MemoryBuffer1D<int, Stride1D.Dense> countSlot,
-		MemoryBuffer1D<ulong, Stride1D.Dense> remainingSlot)
+public readonly struct SmallPrimeFactorScratch
 {
-	public readonly MemoryBuffer1D<ulong, Stride1D.Dense> PrimeSlots = primeSlots;
-	public readonly MemoryBuffer1D<int, Stride1D.Dense> ExponentSlots = exponentSlots;
-	public readonly MemoryBuffer1D<int, Stride1D.Dense> CountSlot = countSlot;
-	public readonly MemoryBuffer1D<ulong, Stride1D.Dense> RemainingSlot = remainingSlot;
+    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 void Clear()
-	{
-		PrimeSlots.MemSetToZero();
-		ExponentSlots.MemSetToZero();
-		CountSlot.MemSetToZero();
-		RemainingSlot.MemSetToZero();
-	}
-}
+    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 readonly struct SpecialMaxScratch(
-	MemoryBuffer1D<ulong, Stride1D.Dense> factorValues,
-	MemoryBuffer1D<ulong, Stride1D.Dense> candidateValues,
-	MemoryBuffer1D<ushort, Stride1D.Dense> resultSlot)
-{
-	public readonly MemoryBuffer1D<ulong, Stride1D.Dense> FactorValues = factorValues;
-	public readonly MemoryBuffer1D<ulong, Stride1D.Dense> CandidateValues = candidateValues;
-	public readonly MemoryBuffer1D<ushort, Stride1D.Dense> ResultSlot = resultSlot;
-
-	public ArrayView1D<ulong, Stride1D.Dense> FactorsView => FactorValues.View;
-	public ArrayView1D<ulong, Stride1D.Dense> CandidatesView => CandidateValues.View;
-	public ArrayView1D<ushort, Stride1D.Dense> ResultView => ResultSlot.View;
+    public void Clear()
+    {
+        PrimeSlots.MemSetToZero();
+        ExponentSlots.MemSetToZero();
+        CountSlot.MemSetToZero();
+        RemainingSlot.MemSetToZero();
+    }
 }
 
 public class GpuKernelPool
 {
-	private static readonly ConcurrentQueue<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.
+    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 KernelContainer GetKernels() => KernelCache.TryDequeue(out var container)
-		? container
-		: new KernelContainer();
+    private static KernelContainer GetKernels(Accelerator accelerator)
+    {
+        return KernelCache.GetOrAdd(accelerator, _ => new KernelContainer());
+    }
 
-	public static void Return(KernelContainer container) => KernelCache.Enqueue(container);
+    // 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;
+        }
 
-	internal static void PreloadStaticTables(KernelContainer kernels, Accelerator accelerator)
-	{
-		EnsureSmallCyclesOnDevice(kernels, accelerator);
-		EnsureSmallPrimesOnDevice(kernels, accelerator);
-		EnsureSmallPrimeFactorTables(kernels, accelerator);
-	}
+        // 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;
+            }
 
-	// 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(KernelContainer kernels, Accelerator accelerator)
-	{
-		if (kernels.SmallCycles is { } buffer)
-		{
-			return buffer.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;
+        }
+    }
 
-		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;
-	}
+    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);
+        }
 
-	public static ResiduePrimeViews EnsureSmallPrimesOnDevice(KernelContainer kernels, Accelerator 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);
-		}
+        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 (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);
-		}
+            var hostLastOne = PrimesGenerator.SmallPrimesLastOne;
+            var hostLastSeven = PrimesGenerator.SmallPrimesLastSeven;
+            var hostLastOnePow2 = PrimesGenerator.SmallPrimesPow2LastOne;
+            var hostLastSevenPow2 = PrimesGenerator.SmallPrimesPow2LastSeven;
 
-		var hostLastOne = PrimesGenerator.SmallPrimesLastOne;
-		var hostLastSeven = PrimesGenerator.SmallPrimesLastSeven;
-		var hostLastOnePow2 = PrimesGenerator.SmallPrimesPow2LastOne;
-		var hostLastSevenPow2 = PrimesGenerator.SmallPrimesPow2LastSeven;
+            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);
 
-		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);
+            kernels.SmallPrimesLastOne = deviceLastOne;
+            kernels.SmallPrimesLastSeven = deviceLastSeven;
+            kernels.SmallPrimesPow2LastOne = deviceLastOnePow2;
+            kernels.SmallPrimesPow2LastSeven = deviceLastSevenPow2;
 
-		kernels.SmallPrimesLastOne = deviceLastOne;
-		kernels.SmallPrimesLastSeven = deviceLastSeven;
-		kernels.SmallPrimesPow2LastOne = deviceLastOnePow2;
-		kernels.SmallPrimesPow2LastSeven = deviceLastSevenPow2;
+            return new ResiduePrimeViews(deviceLastOne.View, deviceLastSeven.View, deviceLastOnePow2.View, deviceLastSevenPow2.View);
+        }
+    }
 
-		return new ResiduePrimeViews(deviceLastOne.View, deviceLastSeven.View, deviceLastOnePow2.View, deviceLastSevenPow2.View);
-	}
+    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);
+        }
 
-	public static SmallPrimeFactorTables EnsureSmallPrimeFactorTables(KernelContainer kernels, Accelerator accelerator)
-	{
-		if (kernels.SmallPrimeFactorsPrimes is { } primeBuffer && kernels.SmallPrimeFactorsSquares is { } squareBuffer)
-		{
-			return new SmallPrimeFactorTables(primeBuffer, squareBuffer, (int)primeBuffer.Length);
-		}
+        lock (kernels)
+        {
+            if (kernels.SmallPrimeFactorsPrimes is { } existingPrimes && kernels.SmallPrimeFactorsSquares is { } existingSquares)
+            {
+                return new SmallPrimeFactorTables(existingPrimes, existingSquares, (int)existingPrimes.Length);
+            }
 
-		if (kernels.SmallPrimeFactorsPrimes is { } existingPrimes && kernels.SmallPrimeFactorsSquares is { } existingSquares)
-		{
-			return new SmallPrimeFactorTables(existingPrimes, existingSquares, (int)existingPrimes.Length);
-		}
+            var hostPrimes = PrimesGenerator.SmallPrimes;
+            var hostSquares = PrimesGenerator.SmallPrimesPow2;
 
-		var hostPrimes = PrimesGenerator.SmallPrimes;
-		var hostSquares = PrimesGenerator.SmallPrimesPow2;
+            var devicePrimes = accelerator.Allocate1D<uint>(hostPrimes.Length);
+            devicePrimes.View.CopyFromCPU(hostPrimes);
+            var deviceSquares = accelerator.Allocate1D<ulong>(hostSquares.Length);
+            deviceSquares.View.CopyFromCPU(hostSquares);
 
-		var devicePrimes = accelerator.Allocate1D<uint>(hostPrimes.Length);
-		devicePrimes.View.CopyFromCPU(hostPrimes);
-		var deviceSquares = accelerator.Allocate1D<ulong>(hostSquares.Length);
-		deviceSquares.View.CopyFromCPU(hostSquares);
+            kernels.SmallPrimeFactorsPrimes = devicePrimes;
+            kernels.SmallPrimeFactorsSquares = deviceSquares;
 
-		kernels.SmallPrimeFactorsPrimes = devicePrimes;
-		kernels.SmallPrimeFactorsSquares = deviceSquares;
+            return new SmallPrimeFactorTables(devicePrimes, deviceSquares, hostPrimes.Length);
+        }
+    }
 
-		return new SmallPrimeFactorTables(devicePrimes, deviceSquares, hostPrimes.Length);
-	}
+    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;
+            }
 
-	public static SmallPrimeFactorScratch EnsureSmallPrimeFactorScratch(KernelContainer kernels, Accelerator accelerator, int slotCount)
-	{
-		MemoryBuffer1D<ulong, Stride1D.Dense>? primeSlots = kernels.SmallPrimeFactorPrimeSlots;
-		if (primeSlots is null || primeSlots.Length < slotCount)
-		{
-			primeSlots?.Dispose();
-			primeSlots = accelerator.Allocate1D<ulong>(slotCount);
-			kernels.SmallPrimeFactorPrimeSlots = primeSlots;
-		}
+            MemoryBuffer1D<int, Stride1D.Dense>? exponentSlots = kernels.SmallPrimeFactorExponentSlots;
+            if (exponentSlots is null || exponentSlots.Length < slotCount)
+            {
+                exponentSlots?.Dispose();
+                exponentSlots = accelerator.Allocate1D<int>(slotCount);
+                kernels.SmallPrimeFactorExponentSlots = exponentSlots;
+            }
 
-		MemoryBuffer1D<int, Stride1D.Dense>? exponentSlots = kernels.SmallPrimeFactorExponentSlots;
-		if (exponentSlots is null || exponentSlots.Length < slotCount)
-		{
-			exponentSlots?.Dispose();
-			exponentSlots = accelerator.Allocate1D<int>(slotCount);
-			kernels.SmallPrimeFactorExponentSlots = exponentSlots;
-		}
+            MemoryBuffer1D<int, Stride1D.Dense>? countSlot = kernels.SmallPrimeFactorCountSlot;
+            if (countSlot is null)
+            {
+                countSlot = accelerator.Allocate1D<int>(1);
+                kernels.SmallPrimeFactorCountSlot = countSlot;
+            }
 
-		MemoryBuffer1D<int, Stride1D.Dense>? countSlot = kernels.SmallPrimeFactorCountSlot;
-		if (countSlot is null)
-		{
-			countSlot = accelerator.Allocate1D<int>(1);
-			kernels.SmallPrimeFactorCountSlot = countSlot;
-		}
+            MemoryBuffer1D<ulong, Stride1D.Dense>? remainingSlot = kernels.SmallPrimeFactorRemainingSlot;
+            if (remainingSlot is null)
+            {
+                remainingSlot = accelerator.Allocate1D<ulong>(1);
+                kernels.SmallPrimeFactorRemainingSlot = remainingSlot;
+            }
 
-		MemoryBuffer1D<ulong, Stride1D.Dense>? remainingSlot = kernels.SmallPrimeFactorRemainingSlot;
-		if (remainingSlot is null)
-		{
-			remainingSlot = accelerator.Allocate1D<ulong>(1);
-			kernels.SmallPrimeFactorRemainingSlot = remainingSlot;
-		}
+            return new SmallPrimeFactorScratch(primeSlots!, exponentSlots!, countSlot!, remainingSlot!);
+        }
+    }
 
-		return new SmallPrimeFactorScratch(primeSlots!, exponentSlots!, countSlot!, remainingSlot!);
-	}
+    public static GpuKernelLease GetKernel(bool useGpuOrder)
+    {
+        var limiter = GpuPrimeWorkLimiter.Acquire();
+        var gpu = Rent();
+        var accelerator = gpu.Accelerator;
+        var kernels = GetKernels(accelerator);
+        return GpuKernelLease.Rent(limiter, gpu, kernels);
+    }
 
-	public static SpecialMaxScratch EnsureSpecialMaxScratch(KernelContainer kernels, Accelerator accelerator, int factorCapacity)
-	{
-		MemoryBuffer1D<ulong, Stride1D.Dense>? factorValues = kernels.SpecialMaxFactors;
-		if (factorValues is null || factorValues.Length < factorCapacity)
-		{
-			factorValues?.Dispose();
-			factorValues = accelerator.Allocate1D<ulong>(factorCapacity);
-			kernels.SpecialMaxFactors = factorValues;
-		}
+    /// <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 accelerator = lease.Accelerator;
+        var stream = accelerator.CreateStream();
+        action(accelerator, stream);
+        stream.Dispose();
+        lease.Dispose();
 
-		MemoryBuffer1D<ulong, Stride1D.Dense>? candidateValues = kernels.SpecialMaxCandidates;
-		if (candidateValues is null || candidateValues.Length < factorCapacity)
-		{
-			candidateValues?.Dispose();
-			candidateValues = accelerator.Allocate1D<ulong>(factorCapacity);
-			kernels.SpecialMaxCandidates = candidateValues;
-		}
-
-		MemoryBuffer1D<ushort, Stride1D.Dense>? resultSlot = kernels.SpecialMaxResult;
-		if (resultSlot is null)
-		{
-			resultSlot = accelerator.Allocate1D<ushort>(1);
-			kernels.SpecialMaxResult = resultSlot;
-		}
-
-		return new SpecialMaxScratch(factorValues!, candidateValues!, resultSlot!);
-	}
-
-	public static GpuKernelLease GetKernel(bool useGpuOrder)
-	{
-		GpuPrimeWorkLimiter.Acquire();
-		var gpu = Rent();
-		var kernels = GetKernels();
-		return GpuKernelLease.Rent(gpu, kernels);
-	}
-
-	/// <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 accelerator = lease.Accelerator;
-		var stream = accelerator.CreateStream();
-		action(accelerator, stream);
-		stream.Dispose();
-		lease.Dispose();
-
-	}
+    }
 }

PerfectNumbers.Core/Gpu/GpuPrimeWorkLimiter.cs

@@ -1,6 +1,3 @@
-using System;
-using System.Threading;
-
 namespace PerfectNumbers.Core.Gpu;
 
 public static class GpuPrimeWorkLimiter
@@ -8,26 +5,41 @@ public static class GpuPrimeWorkLimiter
     private static SemaphoreSlim _semaphore = new(1, int.MaxValue);
     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 Lease Acquire()
     {
-        if (value <= 0)
+        // TODO: Inline the pooled limiter guard from the GpuLimiterThroughputBenchmarks so prime-sieve
+        // GPU jobs stop allocating Lease instances on every acquisition.
+        var sem = _semaphore;
+        // sem.Wait();
+        return new Lease(sem);
+    }
+
+    public static void SetLimit(int value)
+    {
+		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;
+    }
+
+    public sealed class Lease
+    {
+        private readonly SemaphoreSlim _sem;
+
+        internal Lease(SemaphoreSlim sem)
         {
-            value = 1;
+            _sem = sem;
         }
 
-        if (value == _currentLimit)
+        public void Dispose()
         {
-            return;
+            // _sem.Release();
         }
-
-        // 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();
     }
 }
+

PerfectNumbers.Core/Gpu/GpuStaticTableInitializer.cs

@@ -1,39 +0,0 @@
-using System.Collections.Concurrent;
-using System.Collections.Generic;
-using System.Runtime.CompilerServices;
-using ILGPU;
-using ILGPU.Runtime;
-using PerfectNumbers.Core;
-
-namespace PerfectNumbers.Core.Gpu;
-
-internal static class GpuStaticTableInitializer
-{
-    private static readonly ConcurrentDictionary<Accelerator, byte> Initialized = new(AcceleratorReferenceComparer.Instance);
-
-    internal static void EnsureStaticTables(KernelContainer kernels, Accelerator accelerator)
-    {
-        Initialized.GetOrAdd(accelerator, acc =>
-        {
-            PrimeTester.PrimeTesterGpuContextPool.EnsureStaticTables(kernels, acc);
-            GpuKernelPool.PreloadStaticTables(kernels, acc);
-            PrimeOrderGpuHeuristics.PreloadStaticTables( acc);
-            return 0;
-        });
-    }
-
-    private sealed class AcceleratorReferenceComparer : IEqualityComparer<Accelerator>
-    {
-        internal static AcceleratorReferenceComparer Instance { get; } = new();
-
-        public bool Equals(Accelerator? x, Accelerator? y)
-        {
-            return ReferenceEquals(x, y);
-        }
-
-        public int GetHashCode(Accelerator obj)
-        {
-            return RuntimeHelpers.GetHashCode(obj);
-        }
-    }
-}

PerfectNumbers.Core/Gpu/HeuristicGpuDivisorTables.cs

@@ -8,83 +8,21 @@ internal readonly struct HeuristicGpuDivisorTables
 {
         public static readonly HeuristicGpuDivisorTables Shared = default;
 
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding1;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding3;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding7;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding9;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding1;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding3;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding7;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorSquaresEnding9;
         public readonly ArrayView1D<ulong, Stride1D.Dense> GroupADivisors;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> GroupADivisorSquares;
         public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorsEnding1;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorSquaresEnding1;
         public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorsEnding7;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorSquaresEnding7;
         public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorsEnding9;
-        public readonly ArrayView1D<ulong, Stride1D.Dense> GroupBDivisorSquaresEnding9;
 
         public HeuristicGpuDivisorTables(
-                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,
                 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)
+                ArrayView1D<ulong, Stride1D.Dense> groupBDivisorsEnding9)
         {
-                CombinedDivisorsEnding1 = combinedDivisorsEnding1;
-                CombinedDivisorsEnding3 = combinedDivisorsEnding3;
-                CombinedDivisorsEnding7 = combinedDivisorsEnding7;
-                CombinedDivisorsEnding9 = combinedDivisorsEnding9;
-                CombinedDivisorSquaresEnding1 = combinedDivisorSquaresEnding1;
-                CombinedDivisorSquaresEnding3 = combinedDivisorSquaresEnding3;
-                CombinedDivisorSquaresEnding7 = combinedDivisorSquaresEnding7;
-                CombinedDivisorSquaresEnding9 = combinedDivisorSquaresEnding9;
                 GroupADivisors = groupADivisors;
-                GroupADivisorSquares = groupADivisorSquares;
                 GroupBDivisorsEnding1 = groupBDivisorsEnding1;
-                GroupBDivisorSquaresEnding1 = groupBDivisorSquaresEnding1;
                 GroupBDivisorsEnding7 = groupBDivisorsEnding7;
-                GroupBDivisorSquaresEnding7 = groupBDivisorSquaresEnding7;
                 GroupBDivisorsEnding9 = groupBDivisorsEnding9;
-                GroupBDivisorSquaresEnding9 = groupBDivisorSquaresEnding9;
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ArrayView1D<ulong, Stride1D.Dense> SelectCombined(byte ending)
-        {
-                return ending switch
-                {
-                        1 => CombinedDivisorsEnding1,
-                        3 => CombinedDivisorsEnding3,
-                        7 => CombinedDivisorsEnding7,
-                        9 => CombinedDivisorsEnding9,
-                        _ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-                };
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ArrayView1D<ulong, Stride1D.Dense> SelectCombinedSquares(byte ending)
-        {
-                return ending switch
-                {
-                        1 => CombinedDivisorSquaresEnding1,
-                        3 => CombinedDivisorSquaresEnding3,
-                        7 => CombinedDivisorSquaresEnding7,
-                        9 => CombinedDivisorSquaresEnding9,
-                        _ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-                };
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -99,18 +37,6 @@ internal readonly struct HeuristicGpuDivisorTables
                 };
         }
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ArrayView1D<ulong, Stride1D.Dense> SelectGroupBSquares(byte ending)
-        {
-                return ending switch
-                {
-                        1 => GroupBDivisorSquaresEnding1,
-                        7 => GroupBDivisorSquaresEnding7,
-                        9 => GroupBDivisorSquaresEnding9,
-                        _ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-                };
-        }
-
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public ArrayView1D<ulong, Stride1D.Dense> SelectDivisors(HeuristicGpuDivisorTableKind kind, byte ending)
         {
@@ -120,21 +46,6 @@ internal readonly struct HeuristicGpuDivisorTables
                         HeuristicGpuDivisorTableKind.GroupBEnding1 => GroupBDivisorsEnding1,
                         HeuristicGpuDivisorTableKind.GroupBEnding7 => GroupBDivisorsEnding7,
                         HeuristicGpuDivisorTableKind.GroupBEnding9 => GroupBDivisorsEnding9,
-                        HeuristicGpuDivisorTableKind.Combined => SelectCombined(ending),
-                        _ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
-                };
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ArrayView1D<ulong, Stride1D.Dense> SelectDivisorSquares(HeuristicGpuDivisorTableKind kind, byte ending)
-        {
-                return kind switch
-                {
-                        HeuristicGpuDivisorTableKind.GroupA => GroupADivisorSquares,
-                        HeuristicGpuDivisorTableKind.GroupBEnding1 => GroupBDivisorSquaresEnding1,
-                        HeuristicGpuDivisorTableKind.GroupBEnding7 => GroupBDivisorSquaresEnding7,
-                        HeuristicGpuDivisorTableKind.GroupBEnding9 => GroupBDivisorSquaresEnding9,
-                        HeuristicGpuDivisorTableKind.Combined => SelectCombinedSquares(ending),
                         _ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
                 };
         }
@@ -144,3 +55,43 @@ internal readonly struct HeuristicGpuDivisorTables
                 Unsafe.AsRef(in Shared) = tables;
         }
 }
+
+internal readonly struct HeuristicGpuCombinedDivisorTables
+{
+        public static readonly HeuristicGpuCombinedDivisorTables Shared = default;
+
+        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding1;
+        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding3;
+        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding7;
+        public readonly ArrayView1D<ulong, Stride1D.Dense> CombinedDivisorsEnding9;
+
+        public HeuristicGpuCombinedDivisorTables(
+                ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding1,
+                ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding3,
+                ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding7,
+                ArrayView1D<ulong, Stride1D.Dense> combinedDivisorsEnding9)
+        {
+                CombinedDivisorsEnding1 = combinedDivisorsEnding1;
+                CombinedDivisorsEnding3 = combinedDivisorsEnding3;
+                CombinedDivisorsEnding7 = combinedDivisorsEnding7;
+                CombinedDivisorsEnding9 = combinedDivisorsEnding9;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ArrayView1D<ulong, Stride1D.Dense> SelectCombined(byte ending)
+        {
+                return ending switch
+                {
+                        1 => CombinedDivisorsEnding1,
+                        3 => CombinedDivisorsEnding3,
+                        7 => CombinedDivisorsEnding7,
+                        9 => CombinedDivisorsEnding9,
+                        _ => ArrayView1D<ulong, Stride1D.Dense>.Empty,
+                };
+        }
+
+        internal static void InitializeShared(in HeuristicGpuCombinedDivisorTables tables)
+        {
+                Unsafe.AsRef(in Shared) = tables;
+        }
+}

PerfectNumbers.Core/Gpu/Kernels/PrimeOrderSpecialMaxKernels.cs

@@ -1,80 +0,0 @@
-using ILGPU;
-using ILGPU.Runtime;
-using PerfectNumbers.Core;
-
-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<ushort, 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]))
-        {
-            resultOut[0] = 0;
-            return;
-        }
-
-        for (int i = 1; i < actual; i++)
-        {
-            if (stepper.ComputeNextIsUnityGpu(candidates[i]))
-            {
-                resultOut[0] = 0;
-                return;
-            }
-        }
-
-        resultOut[0] = 1;
-    }
-}

PerfectNumbers.Core/Gpu/Kernels/PrimeTesterKernels.cs

@@ -82,30 +82,25 @@ internal static class PrimeTesterKernels
         Index1D index,
         ArrayView<int> resultFlag,
         ulong n,
-        ulong maxDivisorSquare,
+        ulong maxDivisor,
         HeuristicGpuDivisorTableKind tableKind,
-        HeuristicGpuDivisorTables tables)
+        HeuristicGpuDivisorTables tables,
+        HeuristicGpuCombinedDivisorTables combinedTables)
     {
         byte nMod10 = (byte)(n % 10UL);
-        ArrayView1D<ulong, Stride1D.Dense> divisors = tables.SelectDivisors(tableKind, nMod10);
-        ArrayView1D<ulong, Stride1D.Dense> divisorSquares = tables.SelectDivisorSquares(tableKind, nMod10);
+        ArrayView1D<ulong, Stride1D.Dense> divisors = tableKind == HeuristicGpuDivisorTableKind.Combined
+            ? combinedTables.SelectCombined(nMod10)
+            : tables.SelectDivisors(tableKind, nMod10);
 
-        int divisorLength = (int)divisorSquares.Length;
+        int divisorLength = (int)divisors.Length;
         int threadIndex = index;
-        if (threadIndex >= divisorLength)
-        {
-            return;
-        }
+        bool skipThread = threadIndex >= divisorLength;
+        ulong divisor = skipThread ? 1UL : divisors[threadIndex];
+        skipThread = skipThread | (divisor > maxDivisor);
 
-        ulong divisorSquare = divisorSquares[threadIndex];
-        if (divisorSquare > maxDivisorSquare)
-        {
-            return;
-        }
-
-        ulong divisor = divisors[threadIndex];
-        divisor = n % divisor;
-        if (divisor == 0UL)
+        ulong remainder = skipThread ? 1UL : n % divisor;
+        bool hasFactor = !skipThread & (remainder == 0UL);
+        if (hasFactor)
         {
             resultFlag[0] = 1;
         }

PerfectNumbers.Core/Gpu/MersenneNumberIncrementalGpuTester.cs

@@ -31,11 +31,11 @@ public class MersenneNumberIncrementalGpuTester(GpuKernelType kernelType, bool u
         ulong step3 = ((exponent % 3UL) << 1) % 3UL;
         ulong step5 = ((exponent % 5UL) << 1) % 5UL;
         GpuUInt128 twoPGpu = (GpuUInt128)twoP;
-        var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(gpuLease.Kernels, accelerator);
+        var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
         ResiduePrimeViews primeViews = default;
         if (_kernelType == GpuKernelType.Pow2Mod)
         {
-            primeViews = GpuKernelPool.EnsureSmallPrimesOnDevice(gpuLease.Kernels, accelerator);
+            primeViews = GpuKernelPool.EnsureSmallPrimesOnDevice(accelerator);
         }
 
         var orderBuffer = accelerator.Allocate1D<ulong>(batchSize);
@@ -121,7 +121,7 @@ public class MersenneNumberIncrementalGpuTester(GpuKernelType kernelType, bool u
         }
 
         ArrayPool<ulong>.Shared.Return(orderArray);
-		orderBuffer.Dispose();
+        orderBuffer.Dispose();
         gpuLease.Dispose();
     }
 }

PerfectNumbers.Core/Gpu/MersenneNumberLucasLehmerGpuTester.cs

@@ -54,13 +54,13 @@ public class MersenneNumberLucasLehmerGpuTester
             return false;
         }
 
-        GpuPrimeWorkLimiter.Acquire();
+        var limiter = GpuPrimeWorkLimiter.Acquire();
         bool result;
         if (exponent >= 128UL)
         {
             if (!TryGetNttParameters(exponent, out var nttMod, out var primitiveRoot))
             {
-				GpuPrimeWorkLimiter.Release();
+                limiter.Dispose();
                 throw new NotSupportedException("NTT parameters for the given exponent are not available.");
             }
 
@@ -80,7 +80,7 @@ public class MersenneNumberLucasLehmerGpuTester
             gpu.Dispose();
         }
 
-		GpuPrimeWorkLimiter.Release();
+        limiter.Dispose();
         return result;
     }
 

PerfectNumbers.Core/Gpu/MersenneNumberOrderGpuTester.cs

@@ -4,63 +4,62 @@ namespace PerfectNumbers.Core.Gpu;
 
 public class MersenneNumberOrderGpuTester(GpuKernelType kernelType, bool useGpuOrder)
 {
-	private readonly GpuKernelType _kernelType = kernelType;
-	private readonly bool _useGpuOrder = useGpuOrder;
+        private readonly GpuKernelType _kernelType = kernelType;
+        private readonly bool _useGpuOrder = useGpuOrder;
 
-	public void Scan(ulong exponent, UInt128 twoP, LastDigit lastDigit, UInt128 maxK, ref bool isPrime)
-	{
-		var gpuLease = GpuKernelPool.GetKernel(_useGpuOrder);
-		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
+        public void Scan(ulong exponent, UInt128 twoP, LastDigit lastDigit, UInt128 maxK, ref bool isPrime)
+        {
+                var gpuLease = GpuKernelPool.GetKernel(_useGpuOrder);
+                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
 
-		var kernel = _kernelType switch
-		{
-			GpuKernelType.Pow2Mod => gpuLease.Pow2ModOrderKernel,
-			_ => gpuLease.IncrementalOrderKernel,
-		};
+                var kernel = _kernelType switch
+                {
+                        GpuKernelType.Pow2Mod => gpuLease.Pow2ModOrderKernel,
+                        _ => gpuLease.IncrementalOrderKernel,
+                };
 
-		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);
+                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);
 
-		UInt128 remaining;
-		int currentSize;
-		int found = 0;
+                UInt128 remaining;
+                int currentSize;
+                int found = 0;
+                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();
+                        // 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);
 
-		var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(gpuLease.Kernels, accelerator);
-		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();
-			// 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
+                        var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
+                        kernel(stream, currentSize, exponent, (GpuUInt128)twoP, (GpuUInt128)kStart, last, divMul,
+                                        kernelArgs, foundBuffer.View, smallCyclesView);
 
-			// 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);
+                        stream.Synchronize();
+                        foundBuffer.View.CopyToCPU(ref found, 1);
+                        if (found != 0)
+                        {
+                                Volatile.Write(ref isPrime, false);
+                                break;
+                        }
 
-			stream.Synchronize();
-			foundBuffer.View.CopyToCPU(ref found, 1);
-			if (found != 0)
-			{
-				Volatile.Write(ref isPrime, false);
-				break;
-			}
+                        kStart += (UInt128)currentSize;
+                }
 
-			kStart += (UInt128)currentSize;
-		}
-
-		foundBuffer.Dispose();
-		gpuLease.Dispose();
-	}
+                foundBuffer.Dispose();
+                gpuLease.Dispose();
+        }
 }

PerfectNumbers.Core/Gpu/MersenneNumberResidueGpuTester.cs

@@ -26,7 +26,7 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
     // GPU residue variant: check 2^p % q == 1 for q = 2*p*k + 1.
     public void Scan(ulong exponent, UInt128 twoP, LastDigit lastDigit, UInt128 maxK, ref bool isPrime)
     {
-        GpuPrimeWorkLimiter.Acquire();
+        var limiter = GpuPrimeWorkLimiter.Acquire();
         var gpuLease = RentAccelerator();
         var accelerator = gpuLease.Accelerator;
 
@@ -34,16 +34,15 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
 
         var stream = accelerator.CreateStream();
         var kernel = GetPow2ModKernel(accelerator);
-		var resources = RentResources(accelerator, GpuConstants.ScanBatchSize);
-		var gpuKernels = GpuKernelPool.GetKernels();
+        var resources = RentResources(accelerator, GpuConstants.ScanBatchSize);
 
         var orderBuffer = resources.OrderBuffer;
         ulong[] orderArray = resources.OrderArray;
         int batchSize = resources.Capacity;
 
         // Ensure device has small cycles and primes tables for in-kernel lookup
-        var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(gpuKernels, accelerator);
-        ResiduePrimeViews primeViews = GpuKernelPool.EnsureSmallPrimesOnDevice(gpuKernels, accelerator);
+        var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
+        ResiduePrimeViews primeViews = GpuKernelPool.EnsureSmallPrimesOnDevice(accelerator);
 
         UInt128 kStart = 1UL;
         UInt128 limit = maxK + UInt128.One;
@@ -109,10 +108,9 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
 
         ReturnResources(accelerator, resources);
         stream.Dispose();
-		// Monitor.Exit(gpuLease.ExecutionLock);
-		gpuKernels.Dispose();
-		ReturnAccelerator(gpuLease);
-		GpuPrimeWorkLimiter.Release();
+        // Monitor.Exit(gpuLease.ExecutionLock);
+        ReturnAccelerator(gpuLease);
+        limiter.Dispose();
     }
 
     private 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>> GetPow2ModKernel(Accelerator accelerator) =>

PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs

@@ -18,11 +18,6 @@ internal enum GpuPow2ModStatus
 
 internal static partial class PrimeOrderGpuHeuristics
 {
-    internal static void PreloadStaticTables(Accelerator accelerator)
-    {
-        _ = GetSmallPrimeDeviceCache(accelerator);
-    }
-
     private static readonly ConcurrentDictionary<ulong, byte> OverflowedPrimes = new();
     private static readonly ConcurrentDictionary<UInt128, byte> OverflowedPrimesWide = new();
     private static readonly ConcurrentDictionary<Accelerator, Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>> Pow2ModKernelCache = new();

PerfectNumbers.Core/Gpu/SharedGpuContext.cs

@@ -1,19 +0,0 @@
-using System;
-using System.Threading;
-using ILGPU;
-using ILGPU.Runtime;
-
-namespace PerfectNumbers.Core.Gpu;
-
-internal static class SharedGpuContext
-{
-    private static readonly Lazy<Context> s_context = new(() => ILGPU.Context.CreateDefault(), LazyThreadSafetyMode.ExecutionAndPublication);
-    private static readonly Lazy<Device> s_device = new(() => s_context.Value.GetPreferredDevice(false), LazyThreadSafetyMode.ExecutionAndPublication);
-    private static readonly Lazy<Accelerator> s_accelerator = new(() => s_device.Value.CreateAccelerator(s_context.Value), LazyThreadSafetyMode.ExecutionAndPublication);
-
-    internal static Context Context => s_context.Value;
-
-    internal static Device Device => s_device.Value;
-
-    internal static Accelerator Accelerator => s_accelerator.Value;
-}

PerfectNumbers.Core/HeuristicCombinedPrimeTester.cs

@@ -1,4 +1,5 @@
 using Open.Numeric.Primes;
+using System;
 using ILGPU.Runtime;
 using System.Runtime.CompilerServices;
 using PerfectNumbers.Core.Gpu;
@@ -41,20 +42,20 @@ public sealed class HeuristicCombinedPrimeTester
 	}
 
 
-	public static void EnsureInitialized()
-	{
-		// Intentionally left blank. Accessing this method forces the static constructor to run.
-	}
+        public static void EnsureInitialized()
+        {
+        // Intentionally left blank. Accessing this method forces the static constructor to run.
+        }
         
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding1Span => CombinedDivisorsEnding1;
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding3Span => CombinedDivisorsEnding3;
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding7Span => CombinedDivisorsEnding7;
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding9Span => CombinedDivisorsEnding9;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding1Span => CombinedDivisorsEnding1;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding3Span => CombinedDivisorsEnding3;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding7Span => CombinedDivisorsEnding7;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding9Span => CombinedDivisorsEnding9;
         
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding1SquaresSpan => CombinedDivisorsEnding1Squares;
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding3SquaresSpan => CombinedDivisorsEnding3Squares;
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding7SquaresSpan => CombinedDivisorsEnding7Squares;
-	internal static ReadOnlySpan<ulong> CombinedDivisorsEnding9SquaresSpan => CombinedDivisorsEnding9Squares;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding1SquaresSpan => CombinedDivisorsEnding1Squares;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding3SquaresSpan => CombinedDivisorsEnding3Squares;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding7SquaresSpan => CombinedDivisorsEnding7Squares;
+        internal static ReadOnlySpan<ulong> CombinedDivisorsEnding9SquaresSpan => CombinedDivisorsEnding9Squares;
 
 	private const ulong Wheel210 = 210UL;
 
@@ -222,38 +223,57 @@ public sealed class HeuristicCombinedPrimeTester
 	};
 
 
-	private static bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong maxDivisorSquare, byte nMod10)
-	{
-		GpuPrimeWorkLimiter.Acquire();
-		var gpu = PrimeTester.PrimeTesterGpuContextPool.Rent(1);
-		var accelerator = gpu.Accelerator;
-		var kernel = PrimeTester.PrimeTesterGpuContextPool.PrimeTesterGpuContextLease.HeuristicTrialDivisionKernel;
-		var flagView1D = gpu.HeuristicFlag.View;
-		var flagView = flagView1D.AsContiguous();
+        private static bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong maxDivisorSquare, byte nMod10)
+        {
+                var limiter = GpuPrimeWorkLimiter.Acquire();
+                var gpu = PrimeTester.PrimeTesterGpuContextPool.Rent(nMod10, 1, PrimeTester.PrimeTesterGpuContextPool.HeuristicGpuTableScope.GroupABWithCombined);
+                var accelerator = gpu.Accelerator;
+                var kernel = gpu.HeuristicTrialDivisionKernel;
+                var flagView1D = gpu.HeuristicFlag.View;
+                var flagView = flagView1D.AsContiguous();
 
-		bool compositeDetected = false;
-		int divisorLength = GetCombinedDivisors(nMod10).Length;
+                ulong maxDivisor = ComputeMaxDivisorLimit(maxDivisorSquare);
+                bool compositeDetected = false;
+                int divisorLength = GetCombinedDivisors(nMod10).Length;
 
-		int compositeFlag = 0;
-		flagView1D.CopyFromCPU(ref compositeFlag, 1);
-		kernel(
-				divisorLength,
-				flagView,
-				n,
-				maxDivisorSquare,
-				HeuristicGpuDivisorTableKind.Combined,
-				gpu.HeuristicGpuTables);
-		accelerator.Synchronize();
-		flagView1D.CopyToCPU(ref compositeFlag, 1);
-		compositeDetected = compositeFlag != 0;
+                int compositeFlag = 0;
+                flagView1D.CopyFromCPU(ref compositeFlag, 1);
+                kernel(
+                        divisorLength,
+                        flagView,
+                        n,
+                        maxDivisor,
+                        HeuristicGpuDivisorTableKind.Combined,
+                        gpu.HeuristicGpuTables,
+                        gpu.HeuristicCombinedTables);
+                accelerator.Synchronize();
+                flagView1D.CopyToCPU(ref compositeFlag, 1);
+                compositeDetected = compositeFlag != 0;
 
-		gpu.Dispose();
-		GpuPrimeWorkLimiter.Release();
-		return compositeDetected;
-	}
+                gpu.Dispose();
+                limiter.Dispose();
+                return compositeDetected;
+        }
 
 
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        
+        private static ulong ComputeMaxDivisorLimit(ulong maxDivisorSquare)
+        {
+                ulong maxDivisor = (ulong)Math.Sqrt(maxDivisorSquare);
+
+                while ((maxDivisor + 1) != 0 && (maxDivisor + 1) <= maxDivisorSquare / (maxDivisor + 1))
+                {
+                        maxDivisor++;
+                }
+
+                while (maxDivisor != 0 && maxDivisor > maxDivisorSquare / maxDivisor)
+                {
+                        maxDivisor--;
+                }
+
+                return maxDivisor;
+        }
 	private static bool EvaluateWithOpenNumericFallback(ulong n)
 	{
 		return Prime.Numbers.IsPrime(n);

PerfectNumbers.Core/HeuristicPrimeTester.cs

@@ -213,7 +213,7 @@ public sealed class HeuristicPrimeTester
 				int processed = 0;
 				while (processed < interleaveBatchSize)
 				{
-					if (!TrySelectNextGroupBDivisor(endingOrder, indices, maxDivisorSquare, out ulong divisor))
+                    if (!TrySelectNextGroupBDivisor(endingOrder, indices, maxDivisorSquare, out ulong divisor))
 					{
 						groupBHasMore = false;
 						break;
@@ -238,80 +238,100 @@ public sealed class HeuristicPrimeTester
 	}
 
 
-	private bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong maxDivisorSquare, byte nMod10)
-	{
-		GpuPrimeWorkLimiter.Acquire();
-		var gpu = PrimeTester.PrimeTesterGpuContextPool.Rent(1);
-		var accelerator = gpu.Accelerator;
-		var kernel = PrimeTester.PrimeTesterGpuContextPool.PrimeTesterGpuContextLease.HeuristicTrialDivisionKernel;
-		var flagView1D = gpu.HeuristicFlag.View;
-		var flagView = flagView1D.AsContiguous();
+        private bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong maxDivisorSquare, byte nMod10)
+        {
+                var limiter = GpuPrimeWorkLimiter.Acquire();
+                var gpu = PrimeTester.PrimeTesterGpuContextPool.Rent(nMod10, 1, PrimeTester.PrimeTesterGpuContextPool.HeuristicGpuTableScope.GroupAB);
+                var accelerator = gpu.Accelerator;
+                var kernel = gpu.HeuristicTrialDivisionKernel;
+                var flagView1D = gpu.HeuristicFlag.View;
+                var flagView = flagView1D.AsContiguous();
 
-		bool compositeDetected = false;
-		int compositeFlag = 0;
+                ulong maxDivisor = ComputeMaxDivisorLimit(maxDivisorSquare);
+                bool compositeDetected = false;
+                int compositeFlag = 0;
 
-		int groupALength = HeuristicPrimeSieves.GroupADivisors.Length;
+                int groupALength = HeuristicPrimeSieves.GroupADivisors.Length;
 
-		flagView1D.CopyFromCPU(ref compositeFlag, 1);
-		kernel(
-				groupALength,
-				flagView,
-				n,
-				maxDivisorSquare,
-				HeuristicGpuDivisorTableKind.GroupA,
-				gpu.HeuristicGpuTables);
-		accelerator.Synchronize();
-		flagView1D.CopyToCPU(ref compositeFlag, 1);
-		compositeDetected = compositeFlag != 0;
+                flagView1D.CopyFromCPU(ref compositeFlag, 1);
+                kernel(
+                        groupALength,
+                        flagView,
+                        n,
+                        maxDivisor,
+                        HeuristicGpuDivisorTableKind.GroupA,
+                        gpu.HeuristicGpuTables,
+                        gpu.HeuristicCombinedTables);
+                accelerator.Synchronize();
+                flagView1D.CopyToCPU(ref compositeFlag, 1);
+                compositeDetected = compositeFlag != 0;
 
-		if (!compositeDetected)
-		{
-			ReadOnlySpan<byte> endingOrder = GetGroupBEndingOrder(nMod10);
-			for (int i = 0; i < endingOrder.Length && !compositeDetected; i++)
-			{
-				byte ending = endingOrder[i];
-				HeuristicGpuDivisorTableKind tableKind = ending switch
-				{
-					1 => HeuristicGpuDivisorTableKind.GroupBEnding1,
-					7 => HeuristicGpuDivisorTableKind.GroupBEnding7,
-					9 => HeuristicGpuDivisorTableKind.GroupBEnding9,
-					_ => HeuristicGpuDivisorTableKind.GroupA,
-				};
+                if (!compositeDetected)
+                {
+                        ReadOnlySpan<byte> endingOrder = GetGroupBEndingOrder(nMod10);
+                        for (int i = 0; i < endingOrder.Length && !compositeDetected; i++)
+                        {
+                                byte ending = endingOrder[i];
+                                HeuristicGpuDivisorTableKind tableKind = ending switch
+                                {
+                                        1 => HeuristicGpuDivisorTableKind.GroupBEnding1,
+                                        7 => HeuristicGpuDivisorTableKind.GroupBEnding7,
+                                        9 => HeuristicGpuDivisorTableKind.GroupBEnding9,
+                                        _ => HeuristicGpuDivisorTableKind.GroupA,
+                                };
 
-				if (tableKind == HeuristicGpuDivisorTableKind.GroupA)
-				{
-					continue;
-				}
+                                if (tableKind == HeuristicGpuDivisorTableKind.GroupA)
+                                {
+                                        continue;
+                                }
 
-				int divisorLength = GetGroupBDivisors(ending).Length;
+                                int divisorLength = GetGroupBDivisors(ending).Length;
 
-				compositeFlag = 0;
-				flagView1D.CopyFromCPU(ref compositeFlag, 1);
-				kernel(
-						divisorLength,
-						flagView,
-						n,
-						maxDivisorSquare,
-						tableKind,
-						gpu.HeuristicGpuTables);
-				accelerator.Synchronize();
-				flagView1D.CopyToCPU(ref compositeFlag, 1);
-				compositeDetected = compositeFlag != 0;
-			}
-		}
+                                compositeFlag = 0;
+                                flagView1D.CopyFromCPU(ref compositeFlag, 1);
+                                kernel(
+                                        divisorLength,
+                                        flagView,
+                                        n,
+                                        maxDivisor,
+                                        tableKind,
+                                        gpu.HeuristicGpuTables,
+                        gpu.HeuristicCombinedTables);
+                                accelerator.Synchronize();
+                                flagView1D.CopyToCPU(ref compositeFlag, 1);
+                                compositeDetected = compositeFlag != 0;
+                        }
+                }
 
-		gpu.Dispose();
-		GpuPrimeWorkLimiter.Release();
-		return compositeDetected;
-	}
+                gpu.Dispose();
+                limiter.Dispose();
+                return compositeDetected;
+        }
 
 
 
-	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static bool EvaluateWithOpenNumericFallback(ulong n)
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool EvaluateWithOpenNumericFallback(ulong n)
 	{
 		return Prime.Numbers.IsPrime(n);
 	}
+
+	private static ulong ComputeMaxDivisorLimit(ulong maxDivisorSquare)
+	{
+		ulong maxDivisor = (ulong)Math.Sqrt(maxDivisorSquare);
+
+		while ((maxDivisor + 1) != 0 && (maxDivisor + 1) <= maxDivisorSquare / (maxDivisor + 1))
+		{
+			maxDivisor++;
+		}
+
+		while (maxDivisor != 0 && maxDivisor > maxDivisorSquare / maxDivisor)
+		{
+			maxDivisor--;
+		}
+
+		return maxDivisor;
+	}
 	internal static ulong ComputeHeuristicDivisorSquareLimit(ulong n)
 	{
 		return n;
@@ -327,7 +347,7 @@ public sealed class HeuristicPrimeTester
 	};
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
-	private static bool TrySelectNextGroupBDivisor(ReadOnlySpan<byte> endingOrder, Span<int> indices, ulong maxDivisorSquare, out ulong divisor)
+        private static bool TrySelectNextGroupBDivisor(ReadOnlySpan<byte> endingOrder, Span<int> indices, ulong maxDivisorSquare, out ulong divisor)
 	{
 		ulong bestCandidate = ulong.MaxValue;
 		int bestEndingIndex = -1;

PerfectNumbers.Core/MersenneDivisorCycles.cs

@@ -412,7 +412,7 @@ public class MersenneDivisorCycles
 		// Console.WriteLine($"MersenneDivisorCycles.TryFactorIntoCountsInternal hits {Volatile.Read(ref _tryFactorIntoCountsInternalHits)}");
 
 		// HeuristicPrimeTester primeTester = _primeTester ??= new();
-		if (PrimeTester.IsPrimeGpu(remaining))
+		if (PrimeTester.IsPrime(remaining))
 		// if (PrimeTester.IsPrimeCpu(remaining, CancellationToken.None))
 		{
 			AddFactor(counts, remaining);
@@ -943,7 +943,7 @@ public class MersenneDivisorCycles
 		// HeuristicPrimeTester primeTester = _primeTester ??= new();
 		// if (!skipPrimeOrderHeuristic && HeuristicPrimeTester.Exclusive.IsPrimeCpu(divisor, CancellationToken.None))
 		// if (!skipPrimeOrderHeuristic && primeTester.IsPrimeGpu(divisor))
-		if (!skipPrimeOrderHeuristic && PrimeTester.IsPrimeGpu(divisor))
+		if (!skipPrimeOrderHeuristic && PrimeTester.IsPrime(divisor))
 		{
 			ulong computedOrder = PrimeOrderCalculator.Calculate(
 					divisor,

PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Buffers;
 using System.Diagnostics;
 using System.Numerics;
@@ -107,7 +108,7 @@ internal static partial class PrimeOrderCalculator
 		return candidateOrder;
 	}
 
-	// private static ulong specialMaxHits;
+
 	private static bool TrySpecialMaxCpu(ulong phi, ulong prime, PartialFactorResult factors, in MontgomeryDivisorData divisorData)
 	{
 		int length = factors.Count;
@@ -120,16 +121,16 @@ internal static partial class PrimeOrderCalculator
 
 		ReadOnlySpan<FactorEntry> factorSpan = new(factors.Factors, 0, length);
 
-		Span<ulong> stackBuffer = stackalloc ulong[length];
-
-		if (length <= 7)
+		if (length <= 32)
 		{
+			Span<ulong> stackBuffer = stackalloc ulong[length];
 			return EvaluateSpecialMaxCandidates(stackBuffer, factorSpan, phi, prime, divisorData);
 		}
 
-		// Atomic.Add(ref specialMaxHits, 1);
-		// Console.WriteLine($"Special max GPU hit {specialMaxHits} ({length})");
-		return EvaluateSpecialMaxCandidatesGpu(stackBuffer, factorSpan, phi, prime, divisorData);
+		ulong[] rented = ThreadStaticPools.UlongPool.Rent(length);
+		bool result = EvaluateSpecialMaxCandidates(rented.AsSpan(0, length), factorSpan, phi, prime, divisorData);
+		ThreadStaticPools.UlongPool.Return(rented, clearArray: false);
+		return result;
 	}
 
 	private static bool EvaluateSpecialMaxCandidates(Span<ulong> buffer, ReadOnlySpan<FactorEntry> factors, ulong phi, ulong prime, in MontgomeryDivisorData divisorData)
@@ -1193,7 +1194,7 @@ internal static partial class PrimeOrderCalculator
 				// Console.WriteLine($"Partial factor pending hits {Volatile.Read(ref _partialFactorPendingHits)}");
 
 				// bool isPrime = PrimeTester.IsPrimeCpu(composite, CancellationToken.None);
-				bool isPrime = PrimeTester.IsPrimeGpu(composite);
+				bool isPrime = PrimeTester.IsPrime(composite);
 				// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
 
 				entry = entry.WithPrimality(isPrime);
@@ -1230,7 +1231,7 @@ internal static partial class PrimeOrderCalculator
 			// Atomic.Add(ref _partialFactorCofactorHits, 1UL);
 			// Console.WriteLine($"Partial factor cofactor hits {Volatile.Read(ref _partialFactorCofactorHits)}");
 
-			cofactorIsPrime = PrimeTester.IsPrimeGpu(cofactor);
+			cofactorIsPrime = PrimeTester.IsPrime(cofactor);
 			// cofactorIsPrime = PrimeTester.IsPrimeGpu(cofactor);
 			// cofactorIsPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(cofactor);
 		}
@@ -1700,7 +1701,7 @@ internal static partial class PrimeOrderCalculator
 		// HeuristicPrimeTester tester = _tester ??= new();
 
 		// bool isPrime = primeTester.HeuristicIsPrimeGpu(value);
-		bool isPrime = PrimeTester.IsPrimeGpu(value);
+		bool isPrime = PrimeTester.IsPrime(value);
 		// bool isPrime = PrimeTester.IsPrimeGpu(value);
 		// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(value);
 		if (!knownComposite && isPrime)
@@ -1716,7 +1717,7 @@ internal static partial class PrimeOrderCalculator
 		// Console.WriteLine($"Factor completely after PollardRho hits {Volatile.Read(ref _factorCompletelyPollardRhoHits)}");
 
 		// isPrime = primeTester.HeuristicIsPrimeGpu(factor);
-		isPrime = PrimeTester.IsPrimeGpu(factor);
+		isPrime = PrimeTester.IsPrime(factor);
 		// isPrime = PrimeTester.IsPrimeGpu(factor);
 		// isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factor);
 		if (isPrime)
@@ -1753,7 +1754,7 @@ internal static partial class PrimeOrderCalculator
 			// Atomic.Add(ref _partialFactorCofactorHits, 1UL);
 			// Console.WriteLine($"Partial factor cofactor hits {Volatile.Read(ref _partialFactorCofactorHits)}");
 
-			isPrime = PrimeTester.IsPrimeGpu(quotient);
+			isPrime = PrimeTester.IsPrime(quotient);
 			// isPrime = PrimeTester.IsPrimeGpu(quotient);
 			// isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(quotient);
 		}

PerfectNumbers.Core/PrimeOrderCalculator.Gpu.cs

@@ -9,111 +9,63 @@ namespace PerfectNumbers.Core;
 
 internal static partial class PrimeOrderCalculator
 {
-	private static bool IsGpuPow2Allowed => s_pow2ModeInitialized && s_allowGpuPow2;
+        private static bool IsGpuPow2Allowed => s_pow2ModeInitialized && s_allowGpuPow2;
 
-	private const int GpuSmallPrimeFactorSlots = 64;
+        private const int GpuSmallPrimeFactorSlots = 64;
 
-	private static bool TryPopulateSmallPrimeFactorsGpu(ulong value, uint limit, Dictionary<ulong, int> counts, out int factorCount, out ulong remaining)
-	{
-		var primeBufferArray = ThreadStaticPools.UlongPool.Rent(GpuSmallPrimeFactorSlots);
-		var exponentBufferArray = ThreadStaticPools.IntPool.Rent(GpuSmallPrimeFactorSlots);
-		Span<ulong> primeBuffer = primeBufferArray.AsSpan(0, GpuSmallPrimeFactorSlots);
-		Span<int> exponentBuffer = exponentBufferArray.AsSpan(0, GpuSmallPrimeFactorSlots);
-		remaining = value;
+        private static bool TryPopulateSmallPrimeFactorsGpu(ulong value, uint limit, Dictionary<ulong, int> counts, out int factorCount, out ulong remaining)
+        {
+                var primeBufferArray = ThreadStaticPools.UlongPool.Rent(GpuSmallPrimeFactorSlots);
+                var exponentBufferArray = ThreadStaticPools.IntPool.Rent(GpuSmallPrimeFactorSlots);
+                Span<ulong> primeBuffer = primeBufferArray.AsSpan(0, GpuSmallPrimeFactorSlots);
+                Span<int> exponentBuffer = exponentBufferArray.AsSpan(0, GpuSmallPrimeFactorSlots);
+                remaining = value;
 
-		var lease = GpuKernelPool.GetKernel(useGpuOrder: true);
-		Accelerator accelerator = lease.Accelerator;
-		AcceleratorStream stream = lease.Stream;
+                var lease = GpuKernelPool.GetKernel(useGpuOrder: true);
+                Accelerator accelerator = lease.Accelerator;
+                AcceleratorStream stream = lease.Stream;
 
-		SmallPrimeFactorTables tables = GpuKernelPool.EnsureSmallPrimeFactorTables(lease.Kernels, accelerator);
-		SmallPrimeFactorScratch scratch = GpuKernelPool.EnsureSmallPrimeFactorScratch(lease.Kernels, accelerator, GpuSmallPrimeFactorSlots);
+                SmallPrimeFactorTables tables = GpuKernelPool.EnsureSmallPrimeFactorTables(accelerator);
+                SmallPrimeFactorScratch scratch = GpuKernelPool.EnsureSmallPrimeFactorScratch(accelerator, GpuSmallPrimeFactorSlots);
 
-		var kernel = lease.SmallPrimeFactorKernel;
-		kernel(
-				stream,
-				1,
-				value,
-				limit,
-				tables.PrimesView,
-				tables.SquaresView,
-				tables.Count,
-				scratch.PrimeSlots.View,
-				scratch.ExponentSlots.View,
-				scratch.CountSlot.View,
-				scratch.RemainingSlot.View);
+                var kernel = lease.SmallPrimeFactorKernel;
+                kernel(
+                        stream,
+                        1,
+                        value,
+                        limit,
+                        tables.PrimesView,
+                        tables.SquaresView,
+                        tables.Count,
+                        scratch.PrimeSlots.View,
+                        scratch.ExponentSlots.View,
+                        scratch.CountSlot.View,
+                        scratch.RemainingSlot.View);
 
-		stream.Synchronize();
+                stream.Synchronize();
 
-		factorCount = 0;
-		scratch.CountSlot.View.CopyToCPU(ref factorCount, 1);
-		factorCount = Math.Min(factorCount, GpuSmallPrimeFactorSlots);
+                factorCount = 0;
+                scratch.CountSlot.View.CopyToCPU(ref factorCount, 1);
+                factorCount = Math.Min(factorCount, GpuSmallPrimeFactorSlots);
 
-		if (factorCount > 0)
-		{
-			scratch.PrimeSlots.View.CopyToCPU(ref MemoryMarshal.GetReference(primeBuffer), factorCount);
-			scratch.ExponentSlots.View.CopyToCPU(ref MemoryMarshal.GetReference(exponentBuffer), factorCount);
-		}
+                if (factorCount > 0)
+                {
+                        scratch.PrimeSlots.View.CopyToCPU(ref MemoryMarshal.GetReference(primeBuffer), factorCount);
+                        scratch.ExponentSlots.View.CopyToCPU(ref MemoryMarshal.GetReference(exponentBuffer), factorCount);
+                }
 
-		scratch.RemainingSlot.View.CopyToCPU(ref remaining, 1);
+                scratch.RemainingSlot.View.CopyToCPU(ref remaining, 1);
 
-		for (int i = 0; i < factorCount; i++)
-		{
-			ulong primeValue = primeBuffer[i];
-			int exponent = exponentBuffer[i];
-			counts.Add(primeValue, exponent);
-		}
+                for (int i = 0; i < factorCount; i++)
+                {
+                        ulong primeValue = primeBuffer[i];
+                        int exponent = exponentBuffer[i];
+                        counts.Add(primeValue, exponent);
+                }
 
-		lease.Dispose();
-		ThreadStaticPools.UlongPool.Return(primeBufferArray);
-		ThreadStaticPools.IntPool.Return(exponentBufferArray);
-		return true;
-	}
-
-	private static bool EvaluateSpecialMaxCandidatesGpu(
-			Span<ulong> buffer,
-			ReadOnlySpan<FactorEntry> factors,
-			ulong phi,
-			ulong prime,
-			in MontgomeryDivisorData divisorData)
-	{
-		if (factors.Length == 0)
-		{
-			return true;
-		}
-
-		int factorCount = factors.Length;
-		Span<ulong> factorSpan = buffer[..factorCount];
-		for (int i = 0; i < factorCount; i++)
-		{
-			factorSpan[i] = factors[i].Value;
-		}
-
-		var lease = GpuKernelPool.GetKernel(useGpuOrder: true);
-		Accelerator accelerator = lease.Accelerator;
-		AcceleratorStream stream = lease.Stream;
-
-		SpecialMaxScratch scratch = GpuKernelPool.EnsureSpecialMaxScratch(lease.Kernels, accelerator, factorCapacity: factorCount);
-
-		scratch.FactorsView.SubView(0, factorCount).CopyFromCPU(ref MemoryMarshal.GetReference(factorSpan), factorCount);
-
-		var kernel = lease.SpecialMaxKernel;
-		kernel(
-				stream,
-				1,
-				phi,
-				scratch.FactorsView,
-				factorCount,
-				divisorData,
-				scratch.CandidatesView,
-				scratch.ResultView);
-
-		stream.Synchronize();
-
-		ushort result = 0;
-		scratch.ResultView.CopyToCPU(ref result, 1);
-		lease.Dispose();
-
-		return result != 0;
-	}
+                lease.Dispose();
+                ThreadStaticPools.UlongPool.Return(primeBufferArray);
+                ThreadStaticPools.IntPool.Return(exponentBufferArray);
+                return true;
+        }
 }
-

docs/gpu-context-rework-plan.md

@@ -0,0 +1,8 @@
+# GPU context pooling and heuristic divisor updates
+
+- [x] Review existing GPU context pooling in `PerfectNumbers.Core/PrimeTester.cs` and determine shared table allocations that can be scoped per trailing digit.
+- [x] Split `PrimeTesterGpuContextPool` into trailing-digit specific pools so each lease only uploads the divisor tables required for that digit.
+- [x] Update GPU warm-up and rental code paths to pick pools based on `n % 10` and ensure thread-safe reuse.
+- [x] Replace square-table usage in GPU heuristic trial division with square-root limits so divisor tables no longer need squared values on the accelerator.
+- [x] Remove GPU square buffers and adjust kernels, table types, and callers accordingly.
+- [x] Build solution to confirm the new pooling and divisor logic compiles; tests documented in summary.