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Align GPU pow2 heuristics with Montgomery helper

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Marek Lemańczyk committed 2025-10-04 22:40:27 +02:00
1 parent b2a7190c14
commit 72dd69bd53
2 files changed
+10 -32
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PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs
+10 -31
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@@ -4,8 +4,6 @@ using ILGPU;
using ILGPU.Runtime;
using PerfectNumbers.Core;
using System.Runtime.InteropServices;
using System.Numerics;
namespace PerfectNumbers.Core.Gpu;
internal enum GpuPow2ModStatus
@@ -18,7 +16,7 @@ internal enum GpuPow2ModStatus
internal static class PrimeOrderGpuHeuristics
{
private static readonly ConcurrentDictionary<ulong, byte> OverflowedPrimes = new();
private static readonly ConcurrentDictionary<Accelerator, Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, GpuUInt128, ArrayView1D<ulong, Stride1D.Dense>>> Pow2ModKernelCache = new();
private static readonly ConcurrentDictionary<Accelerator, Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>> Pow2ModKernelCache = new();
private static PrimeOrderGpuCapability s_capability = PrimeOrderGpuCapability.Default;
internal static ConcurrentDictionary<ulong, byte> OverflowRegistry => OverflowedPrimes;
@@ -108,7 +106,8 @@ internal static class PrimeOrderGpuHeuristics
exponentBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(exponents), exponents.Length);
remainderBuffer.MemSetToZero();
kernel(stream, exponents.Length, exponentBuffer.View, new GpuUInt128(prime), remainderBuffer.View);
MontgomeryDivisorData divisor = MontgomeryDivisorDataCache.Get(prime);
kernel(stream, exponents.Length, exponentBuffer.View, divisor, remainderBuffer.View);
stream.Synchronize();
@@ -142,44 +141,24 @@ internal static class PrimeOrderGpuHeuristics
return 0UL;
}
ulong result = 1UL % modulus;
ulong baseValue = 2UL % modulus;
ulong remaining = exponent;
while (remaining > 0UL)
{
if ((remaining & 1UL) != 0UL)
{
result = (ulong)(((UInt128)result * baseValue) % modulus);
}
remaining >>= 1;
if (remaining == 0UL)
{
break;
}
baseValue = (ulong)(((UInt128)baseValue * baseValue) % modulus);
}
return result;
MontgomeryDivisorData divisor = MontgomeryDivisorDataCache.Get(modulus);
return exponent.Pow2MontgomeryModWindowed(divisor, keepMontgomery: false);
}
private static Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, GpuUInt128, ArrayView1D<ulong, Stride1D.Dense>> GetPow2ModKernel(Accelerator accelerator)
private static Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>> GetPow2ModKernel(Accelerator accelerator)
{
return Pow2ModKernelCache.GetOrAdd(accelerator, static accel =>
{
var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, GpuUInt128, ArrayView1D<ulong, Stride1D.Dense>>(Pow2ModKernel);
var loaded = accel.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>(Pow2ModKernel);
var kernel = KernelUtil.GetKernel(loaded);
return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, GpuUInt128, ArrayView1D<ulong, Stride1D.Dense>>>();
return kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, MontgomeryDivisorData, ArrayView1D<ulong, Stride1D.Dense>>>();
});
}
private static void Pow2ModKernel(Index1D index, ArrayView1D<ulong, Stride1D.Dense> exponents, GpuUInt128 modulus, ArrayView1D<ulong, Stride1D.Dense> remainders)
private static void Pow2ModKernel(Index1D index, ArrayView1D<ulong, Stride1D.Dense> exponents, MontgomeryDivisorData divisor, ArrayView1D<ulong, Stride1D.Dense> remainders)
{
ulong exponent = exponents[index];
GpuUInt128 result = GpuUInt128.Pow2Mod(exponent, modulus);
remainders[index] = result.Low;
remainders[index] = exponent.Pow2MontgomeryModWindowed(divisor, keepMontgomery: false);
}
internal readonly record struct PrimeOrderGpuCapability(int ModulusBits, int ExponentBits)