288 lines
11 KiB
C#
288 lines
11 KiB
C#
using System.Buffers;
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using System.Collections.Concurrent;
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using System.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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using ILGPU;
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using ILGPU.Runtime;
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using PerfectNumbers.Core.Gpu;
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namespace PerfectNumbers.Core;
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public sealed class DivisorCycleCache
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{
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private const byte ByteZero = 0;
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private const byte ByteOne = 1;
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private const int StackBufferThreshold = 128;
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private readonly ConcurrentDictionary<Accelerator, Action<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>> _gpuKernelCache = new(AcceleratorReferenceComparer.Instance);
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private volatile ulong[] _snapshot;
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private volatile bool _useGpuGeneration = true;
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private readonly int _divisorCyclesBatchSize;
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private static int _sharedDivisorCyclesBatchSize = GpuConstants.GpuCycleStepsPerInvocation;
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public static void SetDivisorCyclesBatchSize(int divisorCyclesBatchSize)
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{
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_sharedDivisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
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}
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public static DivisorCycleCache Shared { get; } = new DivisorCycleCache(_sharedDivisorCyclesBatchSize);
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public int PreferredBatchSize => _divisorCyclesBatchSize;
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private DivisorCycleCache(int divisorCyclesBatchSize)
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{
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_divisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
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_snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
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}
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public void ConfigureGeneratorDevice(bool useGpu)
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{
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_useGpuGeneration = useGpu;
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}
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public void RefreshSnapshot()
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{
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_snapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
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}
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public ulong GetCycleLength(ulong divisor, bool skipPrimeOrderHeuristic = false)
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{
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if (!skipPrimeOrderHeuristic)
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{
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Span<ulong> result = stackalloc ulong[1];
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ReadOnlySpan<ulong> singleDivisor = stackalloc ulong[1] { divisor };
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GetCycleLengths(singleDivisor, result);
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return result[0];
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}
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// The skipPrimeOrderHeuristic path is only used for divisors produced by the CPU by-divisor scanner,
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// which always generates values greater than one. Keep this guard disabled here to avoid repeating the
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// validation already performed by the general GetCycleLengths path.
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// if (divisor <= 1UL)
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// {
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// throw new InvalidDataException("Divisor must be > 1");
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// }
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ulong[] snapshot = _snapshot;
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if (divisor < (ulong)snapshot.Length)
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{
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ulong cached = snapshot[divisor];
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if (cached == 0UL)
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{
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throw new InvalidDataException($"Divisor cycle is missing for {divisor}");
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}
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return cached;
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}
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MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
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return MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData, skipPrimeOrderHeuristic: true);
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}
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public void GetCycleLengths(ReadOnlySpan<ulong> divisors, Span<ulong> cycles)
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{
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ulong[] snapshot = _snapshot;
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int length = divisors.Length;
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int[]? rentedMissing = null;
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Span<int> missingBuffer = length <= StackBufferThreshold
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? stackalloc int[length]
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: new Span<int>(rentedMissing = ArrayPool<int>.Shared.Rent(length), 0, length);
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int missingCount = 0;
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for (int i = 0; i < length; i++)
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{
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ulong divisor = divisors[i];
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if (divisor <= 1UL)
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{
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throw new InvalidDataException("Divisor must be > 1");
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}
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if (divisor < (ulong)snapshot.Length)
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{
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ulong cached = snapshot[divisor];
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if (cached == 0UL)
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{
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throw new InvalidDataException($"Divisor cycle is missing for {divisor}");
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}
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cycles[i] = cached;
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}
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else
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{
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missingBuffer[missingCount++] = i;
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}
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}
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if (missingCount != 0)
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{
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ReadOnlySpan<int> missingIndices = missingBuffer[..missingCount];
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if (_useGpuGeneration)
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{
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ComputeCyclesGpu(divisors, cycles, missingIndices);
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}
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else
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{
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ComputeCyclesCpu(divisors, cycles, missingIndices);
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}
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}
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if (rentedMissing is not null)
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{
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ArrayPool<int>.Shared.Return(rentedMissing, clearArray: false);
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}
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static void ComputeCyclesCpu(ReadOnlySpan<ulong> divisors, Span<ulong> cycles, ReadOnlySpan<int> indices)
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{
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for (int i = 0; i < indices.Length; i++)
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{
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int targetIndex = indices[i];
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ulong divisor = divisors[targetIndex];
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MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
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cycles[targetIndex] = MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData);
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}
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}
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private void ComputeCyclesGpu(ReadOnlySpan<ulong> divisors, Span<ulong> cycles, ReadOnlySpan<int> indices)
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{
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int count = indices.Length;
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ulong[]? rentedDivisors = null;
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Span<ulong> workDivisors = count <= StackBufferThreshold
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? stackalloc ulong[count]
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: new Span<ulong>(rentedDivisors = ArrayPool<ulong>.Shared.Rent(count), 0, count);
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ulong[]? rentedResults = null;
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Span<ulong> workResults = count <= StackBufferThreshold
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? stackalloc ulong[count]
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: new Span<ulong>(rentedResults = ArrayPool<ulong>.Shared.Rent(count), 0, count);
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for (int i = 0; i < count; i++)
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{
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workDivisors[i] = divisors[indices[i]];
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}
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ComputeCyclesGpuCore(workDivisors, workResults);
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for (int i = 0; i < count; i++)
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{
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cycles[indices[i]] = workResults[i];
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}
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if (rentedDivisors is not null)
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{
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ArrayPool<ulong>.Shared.Return(rentedDivisors, clearArray: false);
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ArrayPool<ulong>.Shared.Return(rentedResults!, clearArray: false);
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}
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}
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private void ComputeCyclesGpuCore(ReadOnlySpan<ulong> divisors, Span<ulong> destination)
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{
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int length = divisors.Length;
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var gpuLease = GpuKernelPool.GetKernel(useGpuOrder: true);
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var execution = gpuLease.EnterExecutionScope();
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Accelerator accelerator = gpuLease.Accelerator;
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var kernel = _gpuKernelCache.GetOrAdd(accelerator, LoadKernel);
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using MemoryBuffer1D<ulong, Stride1D.Dense> divisorBuffer = accelerator.Allocate1D<ulong>(length);
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using MemoryBuffer1D<ulong, Stride1D.Dense> powBuffer = accelerator.Allocate1D<ulong>(length);
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using MemoryBuffer1D<ulong, Stride1D.Dense> orderBuffer = accelerator.Allocate1D<ulong>(length);
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using MemoryBuffer1D<ulong, Stride1D.Dense> resultBuffer = accelerator.Allocate1D<ulong>(length);
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using MemoryBuffer1D<byte, Stride1D.Dense> statusBuffer = accelerator.Allocate1D<byte>(length);
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ulong[]? rentedPow = null;
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Span<ulong> powSpan = length <= StackBufferThreshold
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? stackalloc ulong[length]
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: new Span<ulong>(rentedPow = ArrayPool<ulong>.Shared.Rent(length), 0, length);
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ulong[]? rentedOrder = null;
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Span<ulong> orderSpan = length <= StackBufferThreshold
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? stackalloc ulong[length]
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: new Span<ulong>(rentedOrder = ArrayPool<ulong>.Shared.Rent(length), 0, length);
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ulong[]? rentedResult = null;
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Span<ulong> resultSpan = length <= StackBufferThreshold
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? stackalloc ulong[length]
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: new Span<ulong>(rentedResult = ArrayPool<ulong>.Shared.Rent(length), 0, length);
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byte[]? rentedStatus = null;
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Span<byte> statusSpan = length <= StackBufferThreshold
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? stackalloc byte[length]
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: new Span<byte>(rentedStatus = ArrayPool<byte>.Shared.Rent(length), 0, length);
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ref ulong divisorRef = ref MemoryMarshal.GetReference(divisors);
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divisorBuffer.View.CopyFromCPU(ref divisorRef, length);
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for (int i = 0; i < length; i++)
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{
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ulong divisor = divisors[i];
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ulong initialPow = 2UL;
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if (initialPow >= divisor)
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{
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initialPow -= divisor;
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}
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powSpan[i] = initialPow;
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orderSpan[i] = 1UL;
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resultSpan[i] = 0UL;
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statusSpan[i] = ByteZero;
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}
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powBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(powSpan), length);
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orderBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(orderSpan), length);
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resultBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(resultSpan), length);
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statusBuffer.View.CopyFromCPU(ref MemoryMarshal.GetReference(statusSpan), length);
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int pending;
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do
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{
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kernel(length, _divisorCyclesBatchSize, divisorBuffer.View, powBuffer.View, orderBuffer.View, resultBuffer.View, statusBuffer.View);
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accelerator.Synchronize();
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statusBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(statusSpan), length);
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pending = 0;
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for (int i = 0; i < length; i++)
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{
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if (statusSpan[i] == ByteZero)
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{
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pending++;
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}
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}
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}
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while (pending > 0);
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resultBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(resultSpan), length);
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resultSpan.CopyTo(destination);
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if (rentedPow is not null)
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{
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ArrayPool<ulong>.Shared.Return(rentedPow, clearArray: false);
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ArrayPool<ulong>.Shared.Return(rentedOrder!, clearArray: false);
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ArrayPool<ulong>.Shared.Return(rentedResult!, clearArray: false);
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ArrayPool<byte>.Shared.Return(rentedStatus!, clearArray: false);
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}
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execution.Dispose();
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gpuLease.Dispose();
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}
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private static Action<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>> LoadKernel(Accelerator accelerator)
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{
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return accelerator.LoadAutoGroupedStreamKernel<Index1D, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>(DivisorCycleKernels.GpuAdvanceDivisorCyclesKernel);
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}
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private sealed class AcceleratorReferenceComparer : IEqualityComparer<Accelerator>
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{
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internal static AcceleratorReferenceComparer Instance { get; } = new();
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public bool Equals(Accelerator? x, Accelerator? y) => ReferenceEquals(x, y);
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public int GetHashCode(Accelerator obj) => RuntimeHelpers.GetHashCode(obj);
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}
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}
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