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Tighten GPU divisor heuristics and stepper usage

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Marek Lemańczyk committed 2025-10-24 20:50:46 +02:00
1 parent fab9ba0413
commit 868c7a4fd2
1 file changed
+81 -28
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PerfectNumbers.Core/Gpu/MersenneNumberDivisorByDivisorGpuTester.cs
+81 -28
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@@ -23,8 +23,10 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
private ulong _divisorLimit;
// private bool _isConfigured;
private delegate void StepperKernel(Index1D index, in GpuDivisorPartialData divisor, ulong divisorCycle, ulong firstCycleRemainder, ArrayView<ulong> exponents, ArrayView<byte> hits);
private readonly ConcurrentDictionary<Accelerator, Action<Index1D, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>, ArrayView<int>>> _kernelCache = new();
private readonly ConcurrentDictionary<Accelerator, Action<Index1D, GpuDivisorPartialData, ulong, ulong, ArrayView<ulong>, ArrayView<byte>>> _stepperKernelCache = new(AcceleratorReferenceComparer.Instance);
private readonly ConcurrentDictionary<Accelerator, StepperKernel> _stepperKernelCache = new(AcceleratorReferenceComparer.Instance);
private readonly ConcurrentDictionary<Accelerator, ConcurrentBag<BatchResources>> _resourcePools = new(AcceleratorReferenceComparer.Instance);
private readonly ConcurrentBag<GpuContextPool.GpuContextLease> _acceleratorPool = new();
private readonly ConcurrentBag<DivisorScanSession> _sessionPool = new();
@@ -32,8 +34,15 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
private Action<Index1D, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>, ArrayView<int>> GetKernel(Accelerator accelerator) =>
_kernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<ulong>, ArrayView<byte>, ArrayView<int>>(DivisorByDivisorKernels.CheckKernel));
private Action<Index1D, GpuDivisorPartialData, ulong, ulong, ArrayView<ulong>, ArrayView<byte>> GetStepperKernel(Accelerator accelerator) =>
_stepperKernelCache.GetOrAdd(accelerator, acc => acc.LoadAutoGroupedStreamKernel<Index1D, GpuDivisorPartialData, ulong, ulong, ArrayView<ulong>, ArrayView<byte>>(DivisorByDivisorKernels.EvaluateDivisorWithStepperKernel));
private StepperKernel GetStepperKernel(Accelerator accelerator) =>
_stepperKernelCache.GetOrAdd(accelerator, acc =>
{
var kernel = acc.LoadAutoGroupedStreamKernel<Index1D, GpuDivisorPartialData, ulong, ulong, ArrayView<ulong>, ArrayView<byte>>(DivisorByDivisorKernels.EvaluateDivisorWithStepperKernel);
return (Index1D extent, in GpuDivisorPartialData divisor, ulong divisorCycle, ulong firstCycleRemainder, ArrayView<ulong> exponents, ArrayView<byte> hits) =>
{
kernel(extent, divisor, divisorCycle, firstCycleRemainder, exponents, hits);
};
});
public int GpuBatchSize
@@ -198,8 +207,22 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
ulong maxK = maxK128 > ulong.MaxValue ? ulong.MaxValue : (ulong)maxK128;
ulong currentK = 1UL;
byte step10 = (byte)(twoP128 % 10UL);
byte step8 = (byte)(twoP128 % 8UL);
byte step5 = (byte)(twoP128 % 5UL);
byte step3 = (byte)(twoP128 % 3UL);
byte step7 = (byte)(twoP128 % 7UL);
byte step11 = (byte)(twoP128 % 11UL);
UInt128 currentDivisor128 = firstDivisor128;
byte remainder10 = (byte)((ulong)(currentDivisor128 % 10UL));
byte remainder8 = (byte)((ulong)(currentDivisor128 & 7UL));
byte remainder5 = (byte)((ulong)(currentDivisor128 % 5UL));
byte remainder3 = (byte)((ulong)(currentDivisor128 % 3UL));
byte remainder7 = (byte)((ulong)(currentDivisor128 % 7UL));
byte remainder11 = (byte)((ulong)(currentDivisor128 % 11UL));
bool lastIsSeven = (prime & 3UL) == 3UL;
ArrayPool<ulong> ulongPool = ThreadStaticPools.UlongPool;
ulong[] filteredDivisors = ulongPool.Rent(chunkCapacity);
Span<ulong> filteredStorage = filteredDivisors.AsSpan();
@@ -224,17 +247,38 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
int filteredCount = 0;
UInt128 nextDivisor128 = currentDivisor128;
byte localRemainder10 = remainder10;
byte localRemainder8 = remainder8;
byte localRemainder5 = remainder5;
byte localRemainder3 = remainder3;
byte localRemainder7 = remainder7;
byte localRemainder11 = remainder11;
for (int i = 0; i < chunkCount; i++)
{
ulong candidate = (ulong)nextDivisor128;
nextDivisor128 += twoP128;
if (CandidatePassesHeuristics(candidate, lastIsSeven))
if (CandidatePassesHeuristics(localRemainder10, localRemainder8, localRemainder3, localRemainder5, localRemainder7, localRemainder11, lastIsSeven))
{
filteredStorage[filteredCount++] = candidate;
}
nextDivisor128 += twoP128;
localRemainder10 = AddMod(localRemainder10, step10, 10);
localRemainder8 = AddMod(localRemainder8, step8, 8);
localRemainder5 = AddMod(localRemainder5, step5, 5);
localRemainder3 = AddMod(localRemainder3, step3, 3);
localRemainder7 = AddMod(localRemainder7, step7, 7);
localRemainder11 = AddMod(localRemainder11, step11, 11);
}
remainder10 = localRemainder10;
remainder8 = localRemainder8;
remainder5 = localRemainder5;
remainder3 = localRemainder3;
remainder7 = localRemainder7;
remainder11 = localRemainder11;
processedCount += (ulong)chunkCount;
UInt128 lastDivisor128 = nextDivisor128 - twoP128;
@@ -316,42 +360,51 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static bool CandidatePassesHeuristics(ulong candidate, bool lastIsSeven)
private static bool CandidatePassesHeuristics(
byte remainder10,
byte remainder8,
byte remainder3,
byte remainder5,
byte remainder7,
byte remainder11,
bool lastIsSeven)
{
// Mirror the CPU-side divisor screen so the GPU path rejects multiples of 3, 5, 7, and 11
// before resolving cycles, keeping cache lookups aligned with the persisted snapshot.
const ushort DecimalMaskWhenLastIsSeven = (1 << 3) | (1 << 7) | (1 << 9);
const ushort DecimalMaskOtherwise = (1 << 1) | (1 << 3) | (1 << 9);
const byte AcceptableRemainder8Mask = 0b10000010;
const int NonZeroMod3Mask = 0b00000110;
const int NonZeroMod5Mask = 0b00011110;
const int NonZeroMod7Mask = 0b01111110;
const int NonZeroMod11Mask = 0b11111111110;
const int RequiredSmallPrimeMask = 0b1111;
int remainder10 = (int)(candidate % 10UL);
ushort decimalMask = lastIsSeven ? DecimalMaskWhenLastIsSeven : DecimalMaskOtherwise;
if (((decimalMask >> remainder10) & 1) == 0)
{
return false;
}
int remainder8 = (int)(candidate & 7UL);
if (((AcceptableRemainder8Mask >> remainder8) & 1) == 0)
if (remainder8 != 1 && remainder8 != 7)
{
return false;
}
int remainder3 = (int)(candidate % 3UL);
int remainder5 = (int)(candidate % 5UL);
int remainder7 = (int)(candidate % 7UL);
int remainder11 = (int)(candidate % 11UL);
int smallPrimeBits = (NonZeroMod3Mask >> remainder3) & 1;
smallPrimeBits |= ((NonZeroMod5Mask >> remainder5) & 1) << 1;
smallPrimeBits |= ((NonZeroMod7Mask >> remainder7) & 1) << 2;
smallPrimeBits |= ((NonZeroMod11Mask >> remainder11) & 1) << 3;
if (remainder3 == 0 || remainder5 == 0 || remainder7 == 0 || remainder11 == 0)
{
return false;
}
return (smallPrimeBits & RequiredSmallPrimeMask) == RequiredSmallPrimeMask;
return true;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static byte AddMod(byte value, byte delta, byte modulus)
{
int result = value + delta;
if (result >= modulus)
{
result -= modulus;
if (result >= modulus)
{
result -= modulus;
}
}
return (byte)result;
}
@@ -395,7 +448,7 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
private readonly MersenneNumberDivisorByDivisorGpuTester _owner;
private readonly GpuContextPool.GpuContextLease _lease;
private readonly Accelerator _accelerator;
private Action<Index1D, GpuDivisorPartialData, ulong, ulong, ArrayView<ulong>, ArrayView<byte>> _stepperKernel = null!;
private StepperKernel _stepperKernel = null!;
private MemoryBuffer1D<ulong, Stride1D.Dense> _exponentsBuffer = null!;
private MemoryBuffer1D<byte, Stride1D.Dense> _hitBuffer = null!;
private ulong[] _hostBuffer = null!;
@@ -518,7 +571,7 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
// throw new InvalidOperationException("GPU stepper kernel was not initialized.");
// }
stepperKernel(1, cachedData, cycle, firstRemainder, exponentSlice, hitSliceView);
stepperKernel(1, in cachedData, cycle, firstRemainder, exponentSlice, hitSliceView);
Span<byte> hitSlice = hits.Slice(0, length);
hitSliceView.CopyToCPU(ref MemoryMarshal.GetReference(hitSlice), length);