865 lines
28 KiB
C#
865 lines
28 KiB
C#
using System;
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using System.Buffers;
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using System.Collections.Concurrent;
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using Open.Numeric.Primes;
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using System.Collections.Generic;
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using System.Numerics;
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using System.Runtime.CompilerServices;
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using System.Threading;
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using ILGPU;
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using ILGPU.Algorithms;
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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 HeuristicPrimeTester
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{
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static HeuristicPrimeTester()
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{
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HeuristicPrimeSieves.EnsureInitialized();
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}
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// TODO: Don't use these tiny arrays. Hard-code the values / checks instead
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private static readonly ulong[] GroupAConstantDivisors = [3UL, 7UL, 11UL, 13UL];
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private static readonly byte[] GroupAIncrementPattern = [20, 10];
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private static readonly byte[] GroupBEndingOrderMod1 = [9, 1];
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private static readonly byte[] GroupBEndingOrderMod3 = [9, 7];
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private static readonly byte[] GroupBEndingOrderMod7 = [7, 1];
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private static readonly byte[] GroupBEndingOrderMod9 = [9, 7, 1];
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// TODO: Would it speed up things if we implement something like ExponentRemainderStepper,
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// MersenneDivisorResidueStepper, or CycleRemainderStepper work with these?
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private static readonly ushort[] Wheel210ResiduesEnding1 = [1, 11, 31, 41, 61, 71, 101, 121, 131, 151, 181, 191];
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private static readonly ushort[] Wheel210ResiduesEnding7 = [17, 37, 47, 67, 97, 107, 127, 137, 157, 167, 187, 197];
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private static readonly ushort[] Wheel210ResiduesEnding9 = [19, 29, 59, 79, 89, 109, 139, 149, 169, 179, 199, 209];
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private const ulong Wheel210 = 210UL;
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internal const int MaxGroupBSequences = 36;
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private static readonly bool UseHeuristicGroupBTrialDivision = false; // Temporary fallback gate for Group B.
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private static readonly ulong[] HeuristicSmallCycleSnapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
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internal enum HeuristicDivisorGroup : byte
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{
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None = 0,
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GroupAConstant = 1,
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GroupAWheel = 2,
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GroupB = 3,
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}
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internal readonly struct HeuristicDivisorCandidate(ulong value, HeuristicDivisorGroup group, byte ending, byte priorityIndex, ushort wheelResidue)
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{
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public readonly ulong Value = value;
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public readonly HeuristicDivisorGroup Group = group;
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public readonly byte Ending = ending;
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public readonly byte PriorityIndex = priorityIndex;
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public readonly ushort WheelResidue = wheelResidue;
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}
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internal readonly struct HeuristicDivisorPreparation(
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in HeuristicDivisorCandidate candidate,
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in MontgomeryDivisorData divisorData,
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ulong cycleLengthHint,
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bool hasCycleLengthHint)
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{
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public readonly HeuristicDivisorCandidate Candidate = candidate;
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public readonly MontgomeryDivisorData DivisorData = divisorData;
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public readonly ulong CycleLengthHint = cycleLengthHint;
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public readonly bool HasCycleLengthHint = hasCycleLengthHint;
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public readonly bool RequiresCycleComputation = !hasCycleLengthHint;
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}
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public static int HeuristicGpuDivisorBatchSize { get; set; } = 4_096;
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public static int HeuristicDivisorInterleaveBatchSize { get; set; } = 64;
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[ThreadStatic]
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private static HeuristicPrimeTester? _tester;
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public static HeuristicPrimeTester Exclusive => _tester ??= new();
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public bool IsPrimeCpu(ulong n, CancellationToken ct)
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{
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ct.ThrowIfCancellationRequested();
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byte nMod10 = (byte)n.Mod10();
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ulong sqrtLimit = ComputeHeuristicSqrt(n);
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if (sqrtLimit < 3UL)
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{
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return EvaluateWithOpenNumericFallback(n);
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}
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bool includeGroupB = UseHeuristicGroupBTrialDivision;
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return HeuristicTrialDivisionCpu(n, sqrtLimit, nMod10, includeGroupB);
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}
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public bool IsPrimeCpu(ulong n)
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{
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return IsPrimeCpu(n, CancellationToken.None);
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}
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public bool IsPrimeGpu(ulong n)
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{
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byte nMod10 = (byte)n.Mod10();
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ulong sqrtLimit = ComputeHeuristicSqrt(n);
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return IsPrimeGpu(n, sqrtLimit, nMod10);
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}
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public bool IsPrimeGpu(ulong n, ulong sqrtLimit, byte nMod10)
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{
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return HeuristicIsPrimeGpuCore(n, sqrtLimit, nMod10);
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}
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private bool HeuristicIsPrimeGpuCore(ulong n, ulong sqrtLimit, byte nMod10)
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{
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// TODO: Is this condition ever met on the execution path in EvenPerfectBitScanner?
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if (sqrtLimit < 3UL)
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{
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return EvaluateWithOpenNumericFallback(n);
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}
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// if (!UseHeuristicGroupBTrialDivision)
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// {
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// return HeuristicTrialDivisionCpu(n, sqrtLimit, nMod10, includeGroupB: false);
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// }
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bool compositeDetected = HeuristicTrialDivisionGpuDetectsDivisor(n, sqrtLimit, nMod10);
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return !compositeDetected;
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}
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private static bool HeuristicTrialDivisionCpu(ulong n, ulong sqrtLimit, byte nMod10, bool includeGroupB)
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{
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ReadOnlySpan<int> groupADivisors = HeuristicPrimeSieves.GroupADivisors;
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int interleaveBatchSize = Math.Max(1, HeuristicDivisorInterleaveBatchSize);
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int groupAIndex = 0;
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if (!includeGroupB)
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{
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while (groupAIndex < groupADivisors.Length)
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{
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int processed = 0;
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while (processed < interleaveBatchSize && groupAIndex < groupADivisors.Length)
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{
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ulong divisor = (ulong)groupADivisors[groupAIndex];
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if (divisor > sqrtLimit)
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{
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groupAIndex = groupADivisors.Length;
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break;
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}
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if (n % divisor == 0UL)
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{
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return false;
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}
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groupAIndex++;
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processed++;
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}
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if (groupAIndex >= groupADivisors.Length)
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{
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break;
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}
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if ((ulong)groupADivisors[groupAIndex] > sqrtLimit)
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{
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groupAIndex = groupADivisors.Length;
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break;
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}
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}
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return EvaluateWithOpenNumericFallback(n);
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}
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ReadOnlySpan<byte> endingOrder = GetGroupBEndingOrder(nMod10);
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if (endingOrder.IsEmpty)
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{
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return EvaluateWithOpenNumericFallback(n);
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}
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Span<int> indices = endingOrder.Length <= 8
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? stackalloc int[endingOrder.Length]
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: new int[endingOrder.Length];
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bool groupAHasMore = groupAIndex < groupADivisors.Length && (ulong)groupADivisors[groupAIndex] <= sqrtLimit;
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bool groupBHasMore = HasGroupBCandidates(endingOrder, indices, sqrtLimit);
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while (groupAHasMore || groupBHasMore)
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{
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if (groupAHasMore)
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{
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int processed = 0;
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while (processed < interleaveBatchSize && groupAIndex < groupADivisors.Length)
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{
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ulong divisor = (ulong)groupADivisors[groupAIndex];
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if (divisor > sqrtLimit)
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{
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groupAIndex = groupADivisors.Length;
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groupAHasMore = false;
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break;
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}
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if (n % divisor == 0UL)
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{
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return false;
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}
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groupAIndex++;
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processed++;
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}
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if (groupAIndex >= groupADivisors.Length)
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{
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groupAHasMore = false;
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}
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else
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{
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groupAHasMore = (ulong)groupADivisors[groupAIndex] <= sqrtLimit;
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if (!groupAHasMore)
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{
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groupAIndex = groupADivisors.Length;
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}
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}
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}
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if (groupBHasMore)
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{
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int processed = 0;
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while (processed < interleaveBatchSize)
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{
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if (!TrySelectNextGroupBDivisor(endingOrder, indices, sqrtLimit, out ulong divisor))
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{
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groupBHasMore = false;
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break;
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}
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if (n % divisor == 0UL)
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{
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return false;
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}
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processed++;
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}
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if (groupBHasMore)
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{
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groupBHasMore = HasGroupBCandidates(endingOrder, indices, sqrtLimit);
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}
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}
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}
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return true;
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}
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private bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong sqrtLimit, byte nMod10)
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{
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int batchCapacity = HeuristicGpuDivisorBatchSize;
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int interleaveBatchSize = HeuristicDivisorInterleaveBatchSize;
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var divisorPool = ThreadStaticPools.UlongPool;
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ulong[] divisorArray = divisorPool.Rent(batchCapacity);
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var limiter = GpuPrimeWorkLimiter.Acquire();
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var gpu = PrimeTester.PrimeTesterGpuContextPool.Rent(batchCapacity);
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var accelerator = gpu.Accelerator;
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var state = gpu.State;
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bool compositeDetected = false;
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int count = 0;
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var inputView = gpu.Input.View;
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var outputView = gpu.Output.View;
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bool ProcessBatch(int length)
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{
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inputView.CopyFromCPU(ref divisorArray[0], length);
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byte compositeFlag = 0;
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outputView.CopyFromCPU(ref compositeFlag, 1);
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state.HeuristicTrialDivisionKernel(length, inputView, n, outputView);
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accelerator.Synchronize();
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outputView.CopyToCPU(ref compositeFlag, 1);
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return compositeFlag != 0;
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}
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ReadOnlySpan<int> groupADivisors = HeuristicPrimeSieves.GroupADivisors;
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int groupAIndex = 0;
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ReadOnlySpan<byte> endingOrder = GetGroupBEndingOrder(nMod10);
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Span<int> indices = endingOrder.Length <= 8
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? stackalloc int[endingOrder.Length]
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: new int[endingOrder.Length];
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bool groupAHasMore = groupAIndex < groupADivisors.Length && (ulong)groupADivisors[groupAIndex] <= sqrtLimit;
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bool groupBHasMore = !endingOrder.IsEmpty && HasGroupBCandidates(endingOrder, indices, sqrtLimit);
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while (!compositeDetected && (groupAHasMore || groupBHasMore))
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{
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if (groupAHasMore)
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{
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int processed = 0;
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while (processed < interleaveBatchSize && groupAIndex < groupADivisors.Length)
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{
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ulong divisor = (ulong)groupADivisors[groupAIndex];
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if (divisor > sqrtLimit)
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{
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groupAIndex = groupADivisors.Length;
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groupAHasMore = false;
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break;
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}
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divisorArray[count] = divisor;
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count++;
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if (count == batchCapacity)
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{
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if (ProcessBatch(count))
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{
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compositeDetected = true;
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goto Cleanup;
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}
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count = 0;
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}
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groupAIndex++;
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processed++;
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}
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if (groupAIndex >= groupADivisors.Length)
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{
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groupAHasMore = false;
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}
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else
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{
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groupAHasMore = (ulong)groupADivisors[groupAIndex] <= sqrtLimit;
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if (!groupAHasMore)
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{
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groupAIndex = groupADivisors.Length;
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}
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}
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}
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if (!compositeDetected && groupBHasMore)
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{
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int processed = 0;
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while (processed < interleaveBatchSize)
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{
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if (!TrySelectNextGroupBDivisor(endingOrder, indices, sqrtLimit, out ulong divisor))
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{
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groupBHasMore = false;
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break;
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}
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divisorArray[count] = divisor;
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count++;
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if (count == batchCapacity)
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{
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if (ProcessBatch(count))
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{
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compositeDetected = true;
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goto Cleanup;
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}
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count = 0;
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}
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processed++;
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}
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if (groupBHasMore)
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{
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groupBHasMore = HasGroupBCandidates(endingOrder, indices, sqrtLimit);
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}
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}
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}
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if (count > 0 && ProcessBatch(count))
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{
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compositeDetected = true;
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goto Cleanup;
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}
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Cleanup:
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divisorPool.Return(divisorArray);
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gpu.Dispose();
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limiter.Dispose();
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return compositeDetected;
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}
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private static bool EvaluateWithOpenNumericFallback(ulong n)
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{
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return Prime.Numbers.IsPrime(n);
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}
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internal static ulong ComputeHeuristicSqrt(ulong n)
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{
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ulong sqrt = (ulong)Math.Sqrt(n);
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UInt128 square = (UInt128)sqrt * sqrt;
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while (square > n)
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{
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sqrt--;
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square = (UInt128)sqrt * sqrt;
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}
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ulong next = sqrt + 1UL;
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UInt128 nextSquare = (UInt128)next * next;
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while (nextSquare <= n)
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{
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sqrt = next;
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next++;
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nextSquare = (UInt128)next * next;
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}
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return sqrt;
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}
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private static ReadOnlySpan<byte> GetGroupBEndingOrder(byte nMod10) => nMod10 switch
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{
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1 => GroupBEndingOrderMod1,
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3 => GroupBEndingOrderMod3,
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7 => GroupBEndingOrderMod7,
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9 => GroupBEndingOrderMod9,
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_ => ReadOnlySpan<byte>.Empty,
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};
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static bool TrySelectNextGroupBDivisor(ReadOnlySpan<byte> endingOrder, Span<int> indices, ulong sqrtLimit, out ulong divisor)
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{
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ulong bestCandidate = ulong.MaxValue;
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int bestEndingIndex = -1;
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for (int i = 0; i < endingOrder.Length; i++)
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{
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ReadOnlySpan<uint> divisors = GetGroupBDivisors(endingOrder[i]);
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int index = indices[i];
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if ((uint)index >= (uint)divisors.Length)
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{
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continue;
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}
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ulong candidate = (ulong)divisors[index];
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if (candidate > sqrtLimit)
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{
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indices[i] = divisors.Length;
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continue;
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}
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if (bestEndingIndex == -1 || candidate < bestCandidate)
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{
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bestCandidate = candidate;
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bestEndingIndex = i;
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}
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}
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if (bestEndingIndex == -1)
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{
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divisor = 0UL;
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return false;
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}
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divisor = bestCandidate;
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indices[bestEndingIndex]++;
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return true;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static bool HasGroupBCandidates(ReadOnlySpan<byte> endingOrder, Span<int> indices, ulong sqrtLimit)
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{
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for (int i = 0; i < endingOrder.Length; i++)
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{
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ReadOnlySpan<uint> divisors = GetGroupBDivisors(endingOrder[i]);
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int index = indices[i];
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if ((uint)index >= (uint)divisors.Length)
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{
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continue;
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}
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ulong candidate = (ulong)divisors[index];
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if (candidate > sqrtLimit)
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{
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indices[i] = divisors.Length;
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continue;
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}
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return true;
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}
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return false;
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}
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private static ReadOnlySpan<uint> GetGroupBDivisors(byte ending) => ending switch
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{
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1 => DivisorGenerator.SmallPrimesLastOneWithoutLastThree,
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3 => ReadOnlySpan<uint>.Empty,
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7 => DivisorGenerator.SmallPrimesLastSevenWithoutLastThree,
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9 => DivisorGenerator.SmallPrimesLastNineWithoutLastThree,
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_ => ReadOnlySpan<uint>.Empty,
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};
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private static ReadOnlySpan<ushort> GetWheel210ResiduesForEnding(byte ending) => ending switch
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{
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1 => Wheel210ResiduesEnding1,
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7 => Wheel210ResiduesEnding7,
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9 => Wheel210ResiduesEnding9,
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_ => ReadOnlySpan<ushort>.Empty,
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};
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private static int InitializeGroupBStates(byte nMod10, Span<HeuristicGroupBSequenceState> buffer)
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{
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ReadOnlySpan<byte> endings = GetGroupBEndingOrder(nMod10);
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int count = 0;
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for (int priorityIndex = 0; priorityIndex < endings.Length; priorityIndex++)
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{
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ReadOnlySpan<ushort> residues = GetWheel210ResiduesForEnding(endings[priorityIndex]);
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for (int residueIndex = 0; residueIndex < residues.Length; residueIndex++)
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{
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buffer[count++] = new HeuristicGroupBSequenceState(residues[residueIndex], endings[priorityIndex], (byte)priorityIndex);
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}
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}
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return count;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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internal static HeuristicDivisorEnumerator CreateHeuristicDivisorEnumerator(ulong sqrtLimit, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
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{
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return new HeuristicDivisorEnumerator(sqrtLimit, nMod10, groupBBuffer);
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
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internal static MersenneHeuristicDivisorEnumerator CreateMersenneDivisorEnumerator(ulong exponent, ulong maxDivisor)
|
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{
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return new MersenneHeuristicDivisorEnumerator(exponent, maxDivisor);
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}
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|
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
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internal static HeuristicDivisorPreparation PrepareHeuristicDivisor(in HeuristicDivisorCandidate candidate)
|
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{
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ulong divisor = candidate.Value;
|
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MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
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bool hasCycleHint = TryGetCycleLengthHint(divisor, out ulong cycleLength);
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return new HeuristicDivisorPreparation(candidate, divisorData, cycleLength, hasCycleHint);
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
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internal static ulong ResolveHeuristicCycleLength(
|
|
ulong exponent,
|
|
in HeuristicDivisorPreparation preparation,
|
|
out bool cycleFromHint,
|
|
out bool cycleComputed,
|
|
out bool primeOrderFailed)
|
|
{
|
|
if (preparation.HasCycleLengthHint && preparation.CycleLengthHint != 0UL)
|
|
{
|
|
cycleFromHint = true;
|
|
cycleComputed = true;
|
|
primeOrderFailed = false;
|
|
return preparation.CycleLengthHint;
|
|
}
|
|
|
|
ulong divisor = preparation.Candidate.Value;
|
|
MontgomeryDivisorData divisorData = preparation.DivisorData;
|
|
|
|
bool trySuccess = MersenneDivisorCycles.TryCalculateCycleLengthForExponentCpu(
|
|
divisor,
|
|
exponent,
|
|
divisorData,
|
|
out ulong computedCycle,
|
|
out bool primeOrderFailedLocal);
|
|
|
|
if (trySuccess && computedCycle != 0UL)
|
|
{
|
|
cycleFromHint = false;
|
|
cycleComputed = true;
|
|
primeOrderFailed = primeOrderFailedLocal;
|
|
return computedCycle;
|
|
}
|
|
|
|
primeOrderFailed = primeOrderFailedLocal || !trySuccess || computedCycle == 0UL;
|
|
ulong resolvedCycle = MersenneDivisorCycles.CalculateCycleLength(divisor, divisorData, skipPrimeOrderHeuristic: primeOrderFailed);
|
|
cycleFromHint = false;
|
|
cycleComputed = resolvedCycle != 0UL;
|
|
return resolvedCycle;
|
|
}
|
|
|
|
[MethodImpl(MethodImplOptions.AggressiveInlining)]
|
|
internal static bool TryGetCycleLengthHint(ulong divisor, out ulong cycleLength)
|
|
{
|
|
ulong[] snapshot = HeuristicSmallCycleSnapshot;
|
|
if (divisor < (ulong)snapshot.Length)
|
|
{
|
|
cycleLength = snapshot[(int)divisor];
|
|
if (cycleLength != 0UL)
|
|
{
|
|
return true;
|
|
}
|
|
}
|
|
|
|
cycleLength = 0UL;
|
|
return false;
|
|
}
|
|
|
|
internal ref struct HeuristicDivisorEnumerator
|
|
{
|
|
private readonly ulong sqrtLimit;
|
|
private int groupAConstantIndex;
|
|
private ulong groupAWheelCandidate;
|
|
private int groupAIncrementIndex;
|
|
private bool groupAWheelActive;
|
|
private Span<HeuristicGroupBSequenceState> groupBStates;
|
|
|
|
public HeuristicDivisorEnumerator(ulong sqrtLimit, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
|
|
{
|
|
this.sqrtLimit = sqrtLimit;
|
|
groupAConstantIndex = 0;
|
|
groupAWheelCandidate = 23UL;
|
|
groupAIncrementIndex = 0;
|
|
groupAWheelActive = sqrtLimit >= 23UL;
|
|
|
|
int count = InitializeGroupBStates(nMod10, groupBBuffer);
|
|
groupBStates = count == 0 ? Span<HeuristicGroupBSequenceState>.Empty : groupBBuffer[..count];
|
|
|
|
for (int i = 0; i < groupBStates.Length; i++)
|
|
{
|
|
groupBStates[i].TryNormalize();
|
|
}
|
|
}
|
|
|
|
public bool TryGetNext(out HeuristicDivisorCandidate candidate)
|
|
{
|
|
// TODO: Hard-code constant A divisor checks here instead of using an array
|
|
while (groupAConstantIndex < GroupAConstantDivisors.Length)
|
|
{
|
|
ulong value = GroupAConstantDivisors[groupAConstantIndex++];
|
|
if (value > sqrtLimit)
|
|
{
|
|
groupAConstantIndex = GroupAConstantDivisors.Length;
|
|
break;
|
|
}
|
|
|
|
// TODO: We're constantly dividing constants mod 10 which is constant too.
|
|
candidate = new HeuristicDivisorCandidate(value, HeuristicDivisorGroup.GroupAConstant, (byte)(value % 10UL), 0, (ushort)value);
|
|
return true;
|
|
}
|
|
|
|
if (groupAWheelActive)
|
|
{
|
|
ulong value = groupAWheelCandidate;
|
|
if (value <= sqrtLimit)
|
|
{
|
|
candidate = new HeuristicDivisorCandidate(value, HeuristicDivisorGroup.GroupAWheel, 3, 0, (ushort)(value % Wheel210));
|
|
byte increment = GroupAIncrementPattern[groupAIncrementIndex];
|
|
groupAIncrementIndex ^= 1;
|
|
|
|
ulong next = value + increment;
|
|
if (next <= value)
|
|
{
|
|
groupAWheelActive = false;
|
|
}
|
|
else
|
|
{
|
|
groupAWheelCandidate = next;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
groupAWheelActive = false;
|
|
}
|
|
|
|
ulong bestCandidate = ulong.MaxValue;
|
|
int bestIndex = -1;
|
|
|
|
for (int i = 0; i < groupBStates.Length; i++)
|
|
{
|
|
ref HeuristicGroupBSequenceState state = ref groupBStates[i];
|
|
ulong value = state.Candidate;
|
|
if (value == ulong.MaxValue)
|
|
{
|
|
continue;
|
|
}
|
|
|
|
if (value > sqrtLimit)
|
|
{
|
|
state.Candidate = ulong.MaxValue;
|
|
continue;
|
|
}
|
|
|
|
if (bestIndex == -1 || value < bestCandidate ||
|
|
(value == bestCandidate && state.PriorityIndex < groupBStates[bestIndex].PriorityIndex))
|
|
{
|
|
bestCandidate = value;
|
|
bestIndex = i;
|
|
}
|
|
}
|
|
|
|
if (bestIndex == -1)
|
|
{
|
|
candidate = default;
|
|
return false;
|
|
}
|
|
|
|
ref HeuristicGroupBSequenceState bestState = ref groupBStates[bestIndex];
|
|
var result = new HeuristicDivisorCandidate(bestState.Candidate, HeuristicDivisorGroup.GroupB, bestState.Ending, bestState.PriorityIndex, bestState.Residue);
|
|
bestState.Advance();
|
|
candidate = result;
|
|
return true;
|
|
}
|
|
}
|
|
|
|
internal struct HeuristicGroupBSequenceState(ushort residue, byte ending, byte priorityIndex)
|
|
{
|
|
public ulong Candidate = residue;
|
|
public byte PriorityIndex = priorityIndex;
|
|
public byte Ending = ending;
|
|
public ushort Residue = residue;
|
|
|
|
public void TryNormalize()
|
|
{
|
|
ulong candidate = Candidate;
|
|
if (candidate == ulong.MaxValue)
|
|
{
|
|
return;
|
|
}
|
|
|
|
while (candidate <= 13UL)
|
|
{
|
|
ulong next = candidate + Wheel210;
|
|
if (next <= candidate)
|
|
{
|
|
Candidate = ulong.MaxValue;
|
|
return;
|
|
}
|
|
|
|
candidate = next;
|
|
}
|
|
|
|
Candidate = candidate;
|
|
}
|
|
|
|
public void Advance()
|
|
{
|
|
ulong candidate = Candidate;
|
|
if (candidate == ulong.MaxValue)
|
|
{
|
|
return;
|
|
}
|
|
|
|
ulong next = candidate + Wheel210;
|
|
Candidate = next > candidate ? next : ulong.MaxValue;
|
|
}
|
|
|
|
|
|
}
|
|
|
|
internal ref struct MersenneHeuristicDivisorEnumerator
|
|
{
|
|
private readonly GpuUInt128 step;
|
|
private readonly GpuUInt128 limit;
|
|
private GpuUInt128 current;
|
|
private MersenneDivisorResidueStepper residueStepper;
|
|
private bool active;
|
|
private ulong processedCount;
|
|
private ulong lastDivisor;
|
|
|
|
public MersenneHeuristicDivisorEnumerator(ulong exponent, ulong maxDivisor)
|
|
{
|
|
var stepLocal = new GpuUInt128(exponent);
|
|
stepLocal.ShiftLeft(1);
|
|
step = stepLocal;
|
|
|
|
var limitLocal = new GpuUInt128(maxDivisor);
|
|
limit = limitLocal;
|
|
|
|
var firstDivisor = stepLocal;
|
|
firstDivisor.Add(1UL);
|
|
|
|
bool hasCandidates = !stepLocal.IsZero && firstDivisor.CompareTo(limitLocal) <= 0;
|
|
|
|
current = hasCandidates ? firstDivisor : GpuUInt128.Zero;
|
|
residueStepper = hasCandidates ? new MersenneDivisorResidueStepper(exponent, stepLocal, firstDivisor) : default;
|
|
active = hasCandidates;
|
|
processedCount = 0UL;
|
|
lastDivisor = 0UL;
|
|
}
|
|
|
|
public bool TryGetNext(out HeuristicDivisorCandidate candidate)
|
|
{
|
|
while (active)
|
|
{
|
|
ulong value = current.Low;
|
|
processedCount++;
|
|
lastDivisor = value;
|
|
|
|
bool admissible = residueStepper.IsAdmissible();
|
|
|
|
Advance();
|
|
|
|
if (admissible)
|
|
{
|
|
candidate = CreateCandidate(value);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
candidate = default;
|
|
return false;
|
|
}
|
|
|
|
private void Advance()
|
|
{
|
|
GpuUInt128 next = current;
|
|
next.Add(step);
|
|
|
|
if (next.CompareTo(limit) > 0 || next.CompareTo(current) <= 0)
|
|
{
|
|
active = false;
|
|
return;
|
|
}
|
|
|
|
current = next;
|
|
residueStepper.Advance();
|
|
}
|
|
|
|
public ulong ProcessedCount => processedCount;
|
|
|
|
public ulong LastDivisor => lastDivisor;
|
|
|
|
public bool Exhausted => !active;
|
|
|
|
private static HeuristicDivisorCandidate CreateCandidate(ulong value)
|
|
{
|
|
byte ending = (byte)(value % 10UL);
|
|
HeuristicDivisorGroup group;
|
|
|
|
if (value == 3UL || value == 7UL || value == 11UL || value == 13UL)
|
|
{
|
|
group = HeuristicDivisorGroup.GroupAConstant;
|
|
}
|
|
else if (ending == 3)
|
|
{
|
|
group = HeuristicDivisorGroup.GroupAWheel;
|
|
}
|
|
else
|
|
{
|
|
group = HeuristicDivisorGroup.GroupB;
|
|
}
|
|
|
|
ushort residue = (ushort)(value % Wheel210);
|
|
return new HeuristicDivisorCandidate(value, group, ending, 0, residue);
|
|
}
|
|
}
|
|
}
|