66 lines
3.6 KiB
C#
66 lines
3.6 KiB
C#
using ILGPU.Runtime;
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namespace PerfectNumbers.Core.Gpu;
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public class MersenneNumberOrderGpuTester(GpuKernelType kernelType, bool useGpuOrder)
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{
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private readonly GpuKernelType _kernelType = kernelType;
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private readonly bool _useGpuOrder = useGpuOrder;
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public void Scan(ulong exponent, UInt128 twoP, LastDigit lastDigit, UInt128 maxK, ref bool isPrime)
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{
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var gpuLease = GpuKernelPool.GetKernel(_useGpuOrder);
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var accelerator = gpuLease.Accelerator;
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var stream = gpuLease.Stream;
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int batchSize = GpuConstants.ScanBatchSize; // large batch improves GPU occupancy and avoids TDR
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UInt128 kStart = UInt128.One;
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ulong divMul = (ulong)((((UInt128)1 << 64) - UInt128.One) / exponent) + 1UL;
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byte last = lastDigit == LastDigit.Seven ? (byte)1 : (byte)0; // ILGPU kernels do not support bool parameters
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var kernel = _kernelType switch
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{
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GpuKernelType.Pow2Mod => gpuLease.Pow2ModOrderKernel,
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_ => gpuLease.IncrementalOrderKernel,
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};
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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.
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exponent.Mod10_8_5_3Steps(out ulong step10, out ulong step8, out ulong step5, out ulong step3);
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UInt128 remaining;
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int currentSize;
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int found = 0;
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while (kStart <= maxK && Volatile.Read(ref isPrime))
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{
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remaining = maxK - kStart + 1UL;
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currentSize = remaining > (UInt128)batchSize ? batchSize : (int)remaining;
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// This clear is required because the result may not always be set. Remove it after the kernels are modified to always set the result.
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foundBuffer.MemSetToZero();
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// Precompute residue automaton bases for this batch
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UInt128 q0 = twoP * kStart + 1UL;
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// TODO: Replace these modulo recomputations with the divisor-cycle stepping deltas captured in
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// MersenneDivisorCycleLengthGpuBenchmarks so each batch advances via cached residues from the
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// single snapshot block instead of recalculating mod 10/8/5/3 in every iteration.
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q0.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
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var kernelArgs = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
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// Ensure device has small cycles table for early rejections in order kernels
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var smallCyclesView = GpuKernelPool.EnsureSmallCyclesOnDevice(accelerator);
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kernel(stream, currentSize, exponent, (GpuUInt128)twoP, (GpuUInt128)kStart, last, divMul,
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kernelArgs, foundBuffer.View, smallCyclesView);
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stream.Synchronize();
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foundBuffer.View.CopyToCPU(ref found, 1);
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if (found != 0)
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{
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Volatile.Write(ref isPrime, false);
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break;
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}
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kStart += (UInt128)currentSize;
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}
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foundBuffer.Dispose();
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gpuLease.Dispose();
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}
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}
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