Remove Montgomery data from GPU divisor flow

PerfectNumbers.Core/Gpu/GpuDivisorPartialData.cs

@@ -1,5 +1,4 @@
 using System.Runtime.CompilerServices;
-using PerfectNumbers.Core;
 
 namespace PerfectNumbers.Core.Gpu;
 
@@ -7,32 +6,18 @@ internal readonly struct GpuDivisorPartialData
 {
     public readonly ulong Modulus;
     public readonly ReadOnlyGpuUInt128 ModulusWide;
-    private readonly MontgomeryDivisorData _montgomeryData;
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private GpuDivisorPartialData(ulong modulus, ReadOnlyGpuUInt128 modulusWide, in MontgomeryDivisorData montgomeryData)
+    private GpuDivisorPartialData(ulong modulus, in ReadOnlyGpuUInt128 modulusWide)
     {
         Modulus = modulus;
         ModulusWide = modulusWide;
-        _montgomeryData = montgomeryData;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static GpuDivisorPartialData Create(ulong modulus)
     {
-        MontgomeryDivisorData montgomery = MontgomeryDivisorData.FromModulus(modulus);
-        return new GpuDivisorPartialData(modulus, new ReadOnlyGpuUInt128(modulus), in montgomery);
-    }
-
-    [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static GpuDivisorPartialData FromMontgomery(in MontgomeryDivisorData divisor)
-    {
-        return new GpuDivisorPartialData(divisor.Modulus, new ReadOnlyGpuUInt128(divisor.Modulus), in divisor);
-    }
-
-    public MontgomeryDivisorData MontgomeryData
-    {
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        get => _montgomeryData;
+        ReadOnlyGpuUInt128 modulusWide = new(modulus);
+        return new GpuDivisorPartialData(modulus, in modulusWide);
     }
 }

PerfectNumbers.Core/Gpu/Kernels/DivisorByDivisorKernels.cs

@@ -83,30 +83,4 @@ internal static class DivisorByDivisorKernels
         }
     }
 
-    public static void ConvertMontgomeryResultsToHitsKernel(
-        Index1D index,
-        ArrayView<ulong> results,
-        ArrayView<byte> hits)
-    {
-        int globalIndex = index;
-        // EvenPerfectBitScanner launches this kernel with an extent matching the result and hit spans,
-        // so the defensive bounds guard stays commented out to keep the conversion branch-free.
-        // int length = (int)results.Length;
-        // if (globalIndex >= length)
-        // {
-        //     return;
-        // }
-
-        ulong montgomeryResult = results[globalIndex];
-        hits[globalIndex] = montgomeryResult == 1UL ? (byte)1 : (byte)0;
-    }
-
-    public static void ComputeMontgomeryExponentKernel(Index1D index, GpuDivisorPartialData divisor, ArrayView<ulong> exponents, ArrayView<ulong> results)
-    {
-        ulong modulus = divisor.Modulus;
-        // Each divisor flowing through this kernel follows q = 2kp + 1 with k >= 1, so modulus is always odd and exceeds one.
-        ulong exponent = exponents[index];
-        ulong montgomeryResult = ULongExtensions.Pow2MontgomeryModWindowedGpuKeepMontgomery(divisor.MontgomeryData, exponent);
-        results[index] = montgomeryResult;
-    }
 }

PerfectNumbers.Core/Gpu/MersenneNumberDivisorByDivisorGpuTester.cs

@@ -259,7 +259,8 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
             {
                 ulong divisorValue = filteredDivisorsSpan[i];
                 GpuDivisorPartialData divisorDataValue = GpuDivisorPartialData.Create(divisorValue);
-                ulong divisorCycle = ResolveDivisorCycle(divisorValue, prime, divisorDataValue);
+                MontgomeryDivisorData montgomeryData = MontgomeryDivisorData.FromModulus(divisorValue);
+                ulong divisorCycle = ResolveDivisorCycle(divisorValue, prime, in montgomeryData);
                 if (divisorCycle != prime)
                 {
                     continue;
@@ -305,11 +306,11 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static ulong ResolveDivisorCycle(ulong divisor, ulong prime, in GpuDivisorPartialData divisorData)
+    private static ulong ResolveDivisorCycle(ulong divisor, ulong prime, in MontgomeryDivisorData divisorData)
     {
-        if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentGpu(divisor, prime, divisorData, out ulong computedCycle, out bool primeOrderFailed) || computedCycle == 0UL)
+        if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(divisor, prime, divisorData, out ulong computedCycle, out bool primeOrderFailed) || computedCycle == 0UL)
         {
-            return MersenneDivisorCycles.CalculateCycleLengthGpu(divisor, divisorData, skipPrimeOrderHeuristic: primeOrderFailed);
+            return MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData, skipPrimeOrderHeuristic: primeOrderFailed);
         }
 
         return computedCycle;
@@ -459,20 +460,16 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
             //     return;
             // }
 
-            GpuDivisorPartialData cachedData = GpuDivisorPartialData.FromMontgomery(divisorData);
-            if (cachedData.Modulus != divisor)
-            {
-                cachedData = GpuDivisorPartialData.Create(divisor);
-            }
+            GpuDivisorPartialData cachedData = GpuDivisorPartialData.Create(divisor);
 
             ulong cycle = divisorCycle;
             ulong firstPrime = primes[0];
 
             if (cycle == 0UL)
             {
-                if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentGpu(divisor, firstPrime, cachedData, out ulong computedCycle, out bool primeOrderFailed) || computedCycle == 0UL)
+                if (!MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(divisor, firstPrime, divisorData, out ulong computedCycle, out bool primeOrderFailed) || computedCycle == 0UL)
                 {
-                    cycle = MersenneDivisorCycles.CalculateCycleLengthGpu(divisor, cachedData, skipPrimeOrderHeuristic: primeOrderFailed);
+                    cycle = MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData, skipPrimeOrderHeuristic: primeOrderFailed);
                 }
                 else
                 {

PerfectNumbers.Core/MersenneDivisorCycles.cs

@@ -326,103 +326,6 @@ public class MersenneDivisorCycles
         ThreadStaticPools.ReturnFactorCountDictionary(factorCounts);
         return success;
     }
-    public static bool TryCalculateCycleLengthForExponentGpu(
-        ulong divisor,
-        ulong exponent,
-        in MontgomeryDivisorData divisorData,
-        out ulong cycleLength,
-        out bool primeOrderFailed)
-    {
-        cycleLength = 0UL;
-        primeOrderFailed = false;
-
-        if ((divisor & (divisor - 1UL)) == 0UL)
-        {
-            cycleLength = 1UL;
-            return true;
-        }
-
-        if (divisor <= 3UL || exponent <= 1UL)
-        {
-            cycleLength = CalculateCycleLength(divisor, divisorData);
-            return true;
-        }
-
-        ulong computedOrder = PrimeOrderCalculator.Calculate(
-            divisor,
-            previousOrder: null,
-            divisorData,
-            PrimeOrderCalculator.PrimeOrderSearchConfig.HeuristicDefault,
-            PrimeOrderCalculator.PrimeOrderHeuristicDevice.Cpu);
-        if (computedOrder != 0UL)
-        {
-            cycleLength = computedOrder;
-            return true;
-        }
-
-        primeOrderFailed = true;
-
-        ulong phi = divisor - 1UL;
-        // A zero totient would imply divisor == 0, which never occurs on the tested path. Keep the guard documented without
-        // branching in the hot loop.
-        // if (phi == 0UL)
-        // {
-        //     return false;
-        // }
-
-        int twoCount = BitOperations.TrailingZeroCount(phi);
-        ulong reducedPhi = phi >> twoCount;
-        if (reducedPhi == 0UL || (reducedPhi % exponent) != 0UL)
-        {
-            return false;
-        }
-
-        ulong k = reducedPhi / exponent;
-        // k == 0 would indicate reducedPhi < exponent, which the EvenPerfectBitScanner call flow prevents. Document the
-        // assumption instead of branching.
-        // if (k == 0UL)
-        // {
-        //     return false;
-        // }
-
-        Dictionary<ulong, int> factorCounts = ThreadStaticPools.RentFactorCountDictionary();
-        bool success = false;
-
-        if (twoCount > 0)
-        {
-            factorCounts[2UL] = twoCount;
-        }
-
-        bool exponentAccumulated = AccumulateFactors(exponent, factorCounts);
-        bool factorsAccumulated = exponentAccumulated && AccumulateFactors(k, factorCounts);
-
-        if (factorsAccumulated)
-        {
-            cycleLength = ReduceOrder(divisorData, phi, factorCounts);
-            success = true;
-            primeOrderFailed = false;
-        }
-
-        factorCounts.Clear();
-        ThreadStaticPools.ReturnFactorCountDictionary(factorCounts);
-        return success;
-    }
-
-    internal static bool TryCalculateCycleLengthForExponentGpu(
-        ulong divisor,
-        ulong exponent,
-        in GpuDivisorPartialData divisorData,
-        out ulong cycleLength,
-        out bool primeOrderFailed) =>
-        TryCalculateCycleLengthForExponentGpu(divisor, exponent, divisorData.MontgomeryData, out cycleLength, out primeOrderFailed);
-
-    internal static ulong CalculateCycleLengthGpu(
-        ulong divisor,
-        in GpuDivisorPartialData divisorData,
-        bool skipPrimeOrderHeuristic = false)
-    {
-        return CalculateCycleLength(divisor, divisorData.MontgomeryData, skipPrimeOrderHeuristic);
-    }
 
     private static bool AccumulateFactors(
         ulong value,