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Document GPU kernel audit progress

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Marek Lemańczyk committed 2025-10-18 17:42:33 +02:00
1 parent 1e25ea0ccf
commit 6217ea7888
31 files changed
+3496 -3246
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PerfectNumbers.Core/Gpu/MersenneNumberDivisorGpuTester.cs
+1 -44
View File
@@ -1,6 +1,5 @@
using System.Collections.Concurrent;
using ILGPU;
using ILGPU.Algorithms;
using ILGPU.Runtime;
namespace PerfectNumbers.Core.Gpu;
@@ -14,7 +13,7 @@ public sealed class MersenneNumberDivisorGpuTester
private readonly ConcurrentDictionary<Accelerator, MemoryBuffer1D<byte, Stride1D.Dense>> _resultBuffers = new();
private Action<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>> GetKernel(Accelerator accelerator) =>
_kernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>>(Kernel));
_kernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ulong, ReadOnlyGpuUInt128, ArrayView<byte>>(DivisorKernels.Kernel));
public static void BuildDivisorCandidates()
{
@@ -131,47 +130,5 @@ public sealed class MersenneNumberDivisorGpuTester
return true;
}
private static void Kernel(Index1D _, ulong exponent, ReadOnlyGpuUInt128 divisor, ArrayView<byte> result)
{
if (divisor.High == 0UL && divisor.Low <= 1UL)
{
result[0] = 0;
return;
}
GpuUInt128 baseVal;
int x = divisor.High == 0UL
? 63 - XMath.LeadingZeroCount(divisor.Low)
: 127 - XMath.LeadingZeroCount(divisor.High);
ReadOnlyGpuUInt128 readOnlyMod = divisor;
if (x == 0)
{
// TODO: Swap Pow2Mod for the ProcessEightBitWindows helper once Pow2Minus1Mod adopts it;
// GpuPow2ModBenchmarks showed the windowed kernel cutting large divisors from ~51 µs to ~21 µs.
baseVal = GpuUInt128.Pow2Mod(exponent, in readOnlyMod);
result[0] = baseVal.High == 0UL && baseVal.Low == 1UL ? (byte)1 : (byte)0;
return;
}
ulong ux = (ulong)x;
if (x >= 64)
{
baseVal = new GpuUInt128(1UL << (x - 64), 0UL);
}
else
{
baseVal = new GpuUInt128(0UL, 1UL << x);
}
GpuUInt128 pow = baseVal;
pow.ModPow(exponent / ux, in readOnlyMod);
// TODO: Replace this trailing Pow2Mod call with the ProcessEightBitWindows variant once the shared
// windowed helper lands so mixed-radix decompositions benefit from the same GPU speedup.
var part2 = GpuUInt128.Pow2Mod(exponent % ux, in readOnlyMod);
GpuUInt128 product = pow;
ReadOnlyGpuUInt128 part2ReadOnly = part2.AsReadOnly();
product.MulMod(in part2ReadOnly, in readOnlyMod);
result[0] = product.High == 0UL && product.Low == 1UL ? (byte)1 : (byte)0;
}
}