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even-perfect-numbers-scanner/PerfectNumbers.Core/HeuristicCombinedPrimeTester.cs
T

699 lines
24 KiB
C#

using Open.Numeric.Primes;
using ILGPU.Runtime;
using System.Runtime.CompilerServices;
using PerfectNumbers.Core.Gpu;
using PerfectNumbers.Core.Gpu.Accelerators;
using ILGPU;
namespace PerfectNumbers.Core;
public sealed class HeuristicCombinedPrimeTester
{
static HeuristicCombinedPrimeTester()
{
HeuristicPrimeSieves.EnsureInitialized();
CombinedDivisorsEnding1TwoAOneB = BuildCombinedDivisors(1, CombinedDivisorPattern.TwoAOneB, out CombinedDivisorsEnding1TwoAOneBSquares);
CombinedDivisorsEnding3TwoAOneB = BuildCombinedDivisors(3, CombinedDivisorPattern.TwoAOneB, out CombinedDivisorsEnding3TwoAOneBSquares);
CombinedDivisorsEnding7TwoAOneB = BuildCombinedDivisors(7, CombinedDivisorPattern.TwoAOneB, out CombinedDivisorsEnding7TwoAOneBSquares);
CombinedDivisorsEnding9TwoAOneB = BuildCombinedDivisors(9, CombinedDivisorPattern.TwoAOneB, out CombinedDivisorsEnding9TwoAOneBSquares);
CombinedDivisorsEnding1OneAOneB = BuildCombinedDivisors(1, CombinedDivisorPattern.OneAOneB, out CombinedDivisorsEnding1OneAOneBSquares);
CombinedDivisorsEnding3OneAOneB = BuildCombinedDivisors(3, CombinedDivisorPattern.OneAOneB, out CombinedDivisorsEnding3OneAOneBSquares);
CombinedDivisorsEnding7OneAOneB = BuildCombinedDivisors(7, CombinedDivisorPattern.OneAOneB, out CombinedDivisorsEnding7OneAOneBSquares);
CombinedDivisorsEnding9OneAOneB = BuildCombinedDivisors(9, CombinedDivisorPattern.OneAOneB, out CombinedDivisorsEnding9OneAOneBSquares);
CombinedDivisorsEnding1ThreeAOneB = BuildCombinedDivisors(1, CombinedDivisorPattern.ThreeAOneB, out CombinedDivisorsEnding1ThreeAOneBSquares);
CombinedDivisorsEnding3ThreeAOneB = BuildCombinedDivisors(3, CombinedDivisorPattern.ThreeAOneB, out CombinedDivisorsEnding3ThreeAOneBSquares);
CombinedDivisorsEnding7ThreeAOneB = BuildCombinedDivisors(7, CombinedDivisorPattern.ThreeAOneB, out CombinedDivisorsEnding7ThreeAOneBSquares);
CombinedDivisorsEnding9ThreeAOneB = BuildCombinedDivisors(9, CombinedDivisorPattern.ThreeAOneB, out CombinedDivisorsEnding9ThreeAOneBSquares);
CombinedDivisorsEnding1ThreeATwoB = BuildCombinedDivisors(1, CombinedDivisorPattern.ThreeATwoB, out CombinedDivisorsEnding1ThreeATwoBSquares);
CombinedDivisorsEnding3ThreeATwoB = BuildCombinedDivisors(3, CombinedDivisorPattern.ThreeATwoB, out CombinedDivisorsEnding3ThreeATwoBSquares);
CombinedDivisorsEnding7ThreeATwoB = BuildCombinedDivisors(7, CombinedDivisorPattern.ThreeATwoB, out CombinedDivisorsEnding7ThreeATwoBSquares);
CombinedDivisorsEnding9ThreeATwoB = BuildCombinedDivisors(9, CombinedDivisorPattern.ThreeATwoB, out CombinedDivisorsEnding9ThreeATwoBSquares);
CombinedDivisorsEnding1 = CombinedDivisorsEnding1OneAOneB;
CombinedDivisorsEnding3 = CombinedDivisorsEnding3OneAOneB;
CombinedDivisorsEnding7 = CombinedDivisorsEnding7OneAOneB;
CombinedDivisorsEnding9 = CombinedDivisorsEnding9OneAOneB;
CombinedDivisorsEnding1Squares = CombinedDivisorsEnding1OneAOneBSquares;
CombinedDivisorsEnding3Squares = CombinedDivisorsEnding3OneAOneBSquares;
CombinedDivisorsEnding7Squares = CombinedDivisorsEnding7OneAOneBSquares;
CombinedDivisorsEnding9Squares = CombinedDivisorsEnding9OneAOneBSquares;
}
public static void EnsureInitialized()
{
// Intentionally left blank. Accessing this method forces the static constructor to run.
}
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding1Span => CombinedDivisorsEnding1;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding3Span => CombinedDivisorsEnding3;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding7Span => CombinedDivisorsEnding7;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding9Span => CombinedDivisorsEnding9;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding1SquaresSpan => CombinedDivisorsEnding1Squares;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding3SquaresSpan => CombinedDivisorsEnding3Squares;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding7SquaresSpan => CombinedDivisorsEnding7Squares;
internal static ReadOnlySpan<ulong> CombinedDivisorsEnding9SquaresSpan => CombinedDivisorsEnding9Squares;
private const ulong Wheel210 = 210UL;
private static readonly ulong[] CombinedDivisorsEnding1TwoAOneB;
private static readonly ulong[] CombinedDivisorsEnding3TwoAOneB;
private static readonly ulong[] CombinedDivisorsEnding7TwoAOneB;
private static readonly ulong[] CombinedDivisorsEnding9TwoAOneB;
private static readonly ulong[] CombinedDivisorsEnding1OneAOneB;
private static readonly ulong[] CombinedDivisorsEnding3OneAOneB;
private static readonly ulong[] CombinedDivisorsEnding7OneAOneB;
private static readonly ulong[] CombinedDivisorsEnding9OneAOneB;
private static readonly ulong[] CombinedDivisorsEnding1ThreeAOneB;
private static readonly ulong[] CombinedDivisorsEnding3ThreeAOneB;
private static readonly ulong[] CombinedDivisorsEnding7ThreeAOneB;
private static readonly ulong[] CombinedDivisorsEnding9ThreeAOneB;
private static readonly ulong[] CombinedDivisorsEnding1ThreeATwoB;
private static readonly ulong[] CombinedDivisorsEnding3ThreeATwoB;
private static readonly ulong[] CombinedDivisorsEnding7ThreeATwoB;
private static readonly ulong[] CombinedDivisorsEnding9ThreeATwoB;
internal static readonly ulong[] CombinedDivisorsEnding1;
internal static readonly ulong[] CombinedDivisorsEnding3;
internal static readonly ulong[] CombinedDivisorsEnding7;
internal static readonly ulong[] CombinedDivisorsEnding9;
private static readonly ulong[] CombinedDivisorsEnding1TwoAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding3TwoAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding7TwoAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding9TwoAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding1OneAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding3OneAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding7OneAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding9OneAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding1ThreeAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding3ThreeAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding7ThreeAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding9ThreeAOneBSquares;
private static readonly ulong[] CombinedDivisorsEnding1ThreeATwoBSquares;
private static readonly ulong[] CombinedDivisorsEnding3ThreeATwoBSquares;
private static readonly ulong[] CombinedDivisorsEnding7ThreeATwoBSquares;
private static readonly ulong[] CombinedDivisorsEnding9ThreeATwoBSquares;
internal static readonly ulong[] CombinedDivisorsEnding1Squares;
internal static readonly ulong[] CombinedDivisorsEnding3Squares;
internal static readonly ulong[] CombinedDivisorsEnding7Squares;
internal static readonly ulong[] CombinedDivisorsEnding9Squares;
private static readonly ulong[] HeuristicSmallCycleSnapshot = MersenneDivisorCycles.Shared.ExportSmallCyclesSnapshot();
internal enum CombinedDivisorPattern : byte
{
TwoAOneB = 0,
OneAOneB = 1,
ThreeAOneB = 2,
ThreeATwoB = 3,
}
internal enum HeuristicDivisorGroup : byte
{
None = 0,
GroupAConstant = 1,
GroupAWheel = 2,
GroupB = 3,
}
internal readonly struct HeuristicDivisorCandidate(ulong value, HeuristicDivisorGroup group, byte ending, byte priorityIndex, ushort wheelResidue)
{
public readonly ulong Value = value;
public readonly HeuristicDivisorGroup Group = group;
public readonly byte Ending = ending;
public readonly byte PriorityIndex = priorityIndex;
public readonly ushort WheelResidue = wheelResidue;
}
internal readonly struct HeuristicDivisorPreparation(
in HeuristicDivisorCandidate candidate,
in MontgomeryDivisorData divisorData,
ulong cycleLengthHint,
bool hasCycleLengthHint)
{
public readonly HeuristicDivisorCandidate Candidate = candidate;
public readonly MontgomeryDivisorData DivisorData = divisorData;
public readonly ulong CycleLengthHint = cycleLengthHint;
public readonly bool HasCycleLengthHint = hasCycleLengthHint;
public readonly bool RequiresCycleComputation = !hasCycleLengthHint;
}
[ThreadStatic]
private static HeuristicCombinedPrimeTester? _tester;
public static HeuristicCombinedPrimeTester Exclusive => _tester ??= new();
public static bool IsPrimeCpu(ulong n)
{
byte nMod10 = (byte)n.Mod10();
ulong maxDivisorSquare = ComputeHeuristicDivisorSquareLimit(n);
if (maxDivisorSquare < 9UL)
{
return EvaluateWithOpenNumericFallback(n);
}
return HeuristicTrialDivisionCpu(n, maxDivisorSquare, nMod10);
}
public static bool IsPrimeGpu(ulong n)
{
byte nMod10 = (byte)n.Mod10();
ulong maxDivisorSquare = ComputeHeuristicDivisorSquareLimit(n);
var gpu = PrimeOrderCalculatorAccelerator.Rent(1);
bool isPrime = IsPrimeGpu(gpu, n, maxDivisorSquare, nMod10);
PrimeOrderCalculatorAccelerator.Return(gpu);
return isPrime;
}
public static bool IsPrimeGpu(PrimeOrderCalculatorAccelerator gpu, ulong n)
{
byte nMod10 = (byte)n.Mod10();
ulong maxDivisorSquare = ComputeHeuristicDivisorSquareLimit(n);
return IsPrimeGpu(gpu, n, maxDivisorSquare, nMod10);
}
public static bool IsPrimeGpu(PrimeOrderCalculatorAccelerator gpu, ulong n, ulong maxDivisorSquare, byte nMod10)
{
// TODO: Is this condition ever met on the execution path in EvenPerfectBitScanner?
if (maxDivisorSquare < 9UL)
{
return EvaluateWithOpenNumericFallback(n);
}
bool compositeDetected = HeuristicTrialDivisionGpuDetectsDivisor(gpu, n, maxDivisorSquare, nMod10);
return !compositeDetected;
}
private static bool HeuristicTrialDivisionCpu(ulong n, ulong maxDivisorSquare, byte nMod10)
{
ReadOnlySpan<ulong> combinedDivisors = GetCombinedDivisors(nMod10);
ReadOnlySpan<ulong> combinedDivisorSquares = GetCombinedDivisorSquares(nMod10);
int length = combinedDivisors.Length;
for (int i = 0; i < length; i++)
{
ulong divisorSquare = combinedDivisorSquares[i];
if (divisorSquare > maxDivisorSquare)
{
break;
}
if (n % combinedDivisors[i] == 0UL)
{
return false;
}
}
return EvaluateWithOpenNumericFallback(n);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static int GetBatchSize(ulong n) => n switch
{
< 1_000 => 8,
< 10_000 => 16,
< 100_000 => 32,
< 1_000_000 => 128,
_ => 256,
};
private static bool HeuristicTrialDivisionGpuDetectsDivisor(PrimeOrderCalculatorAccelerator gpu, ulong n, ulong maxDivisorSquare, byte nMod10)
{
var acceleratorIndex = gpu.AcceleratorIndex;
var stream = AcceleratorStreamPool.Rent(acceleratorIndex);
var kernel = gpu.HeuristicCombinedTrialDivisionKernel;
var flagView1D = gpu.OutputInt!.View;
bool compositeDetected = false;
int divisorLength = GetCombinedDivisors(nMod10).Length;
int compositeFlag = 0;
flagView1D.CopyFromCPU(stream, ref compositeFlag, 1);
var kernelLauncher = kernel.CreateLauncherDelegate<Action<AcceleratorStream, Index1D, byte, ArrayView<int>, ulong, ulong, HeuristicGpuCombinedDivisorTables>>();
kernelLauncher(
stream,
1,
nMod10,
flagView1D,
n,
maxDivisorSquare,
gpu.DivisorTables);
flagView1D.CopyToCPU(stream, ref compositeFlag, 1);
stream.Synchronize();
AcceleratorStreamPool.Return(acceleratorIndex, stream);
// GpuPrimeWorkLimiter.Release();
compositeDetected = compositeFlag != 0;
return compositeDetected;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static bool EvaluateWithOpenNumericFallback(ulong n)
{
return Prime.Numbers.IsPrime(n);
}
internal static ulong ComputeHeuristicDivisorSquareLimit(ulong n)
{
return n;
}
private static ReadOnlySpan<ulong> GetCombinedDivisors(byte nMod10) => nMod10 switch
{
1 => CombinedDivisorsEnding1,
3 => CombinedDivisorsEnding3,
7 => CombinedDivisorsEnding7,
9 => CombinedDivisorsEnding9,
_ => throw new InvalidOperationException($"Unsupported combined divisor selector for digit {nMod10}."),
};
private static ReadOnlySpan<ulong> GetCombinedDivisorSquares(byte nMod10) => nMod10 switch
{
1 => CombinedDivisorsEnding1Squares,
3 => CombinedDivisorsEnding3Squares,
7 => CombinedDivisorsEnding7Squares,
9 => CombinedDivisorsEnding9Squares,
_ => throw new InvalidOperationException($"Unsupported combined divisor square selector for digit {nMod10}."),
};
internal static ReadOnlySpan<ulong> GetCombinedDivisors(byte nMod10, CombinedDivisorPattern pattern) => pattern switch
{
CombinedDivisorPattern.TwoAOneB => nMod10 switch
{
1 => CombinedDivisorsEnding1TwoAOneB,
3 => CombinedDivisorsEnding3TwoAOneB,
7 => CombinedDivisorsEnding7TwoAOneB,
9 => CombinedDivisorsEnding9TwoAOneB,
_ => throw new InvalidOperationException($"Unsupported combined divisor selector for digit {nMod10}."),
},
CombinedDivisorPattern.OneAOneB => nMod10 switch
{
1 => CombinedDivisorsEnding1OneAOneB,
3 => CombinedDivisorsEnding3OneAOneB,
7 => CombinedDivisorsEnding7OneAOneB,
9 => CombinedDivisorsEnding9OneAOneB,
_ => throw new InvalidOperationException($"Unsupported combined divisor selector for digit {nMod10}."),
},
CombinedDivisorPattern.ThreeAOneB => nMod10 switch
{
1 => CombinedDivisorsEnding1ThreeAOneB,
3 => CombinedDivisorsEnding3ThreeAOneB,
7 => CombinedDivisorsEnding7ThreeAOneB,
9 => CombinedDivisorsEnding9ThreeAOneB,
_ => throw new InvalidOperationException($"Unsupported combined divisor selector for digit {nMod10}."),
},
CombinedDivisorPattern.ThreeATwoB => nMod10 switch
{
1 => CombinedDivisorsEnding1ThreeATwoB,
3 => CombinedDivisorsEnding3ThreeATwoB,
7 => CombinedDivisorsEnding7ThreeATwoB,
9 => CombinedDivisorsEnding9ThreeATwoB,
_ => throw new InvalidOperationException($"Unsupported combined divisor selector for digit {nMod10}."),
},
_ => throw new InvalidOperationException($"Unsupported combined divisor pattern: {pattern}."),
};
internal static ReadOnlySpan<ulong> GetCombinedDivisorSquares(byte nMod10, CombinedDivisorPattern pattern) => pattern switch
{
CombinedDivisorPattern.TwoAOneB => nMod10 switch
{
1 => CombinedDivisorsEnding1TwoAOneBSquares,
3 => CombinedDivisorsEnding3TwoAOneBSquares,
7 => CombinedDivisorsEnding7TwoAOneBSquares,
9 => CombinedDivisorsEnding9TwoAOneBSquares,
_ => throw new InvalidOperationException($"Unsupported combined divisor square selector for digit {nMod10}."),
},
CombinedDivisorPattern.OneAOneB => nMod10 switch
{
1 => CombinedDivisorsEnding1OneAOneBSquares,
3 => CombinedDivisorsEnding3OneAOneBSquares,
7 => CombinedDivisorsEnding7OneAOneBSquares,
9 => CombinedDivisorsEnding9OneAOneBSquares,
_ => throw new InvalidOperationException($"Unsupported combined divisor square selector for digit {nMod10}."),
},
CombinedDivisorPattern.ThreeAOneB => nMod10 switch
{
1 => CombinedDivisorsEnding1ThreeAOneBSquares,
3 => CombinedDivisorsEnding3ThreeAOneBSquares,
7 => CombinedDivisorsEnding7ThreeAOneBSquares,
9 => CombinedDivisorsEnding9ThreeAOneBSquares,
_ => throw new InvalidOperationException($"Unsupported combined divisor square selector for digit {nMod10}."),
},
CombinedDivisorPattern.ThreeATwoB => nMod10 switch
{
1 => CombinedDivisorsEnding1ThreeATwoBSquares,
3 => CombinedDivisorsEnding3ThreeATwoBSquares,
7 => CombinedDivisorsEnding7ThreeATwoBSquares,
9 => CombinedDivisorsEnding9ThreeATwoBSquares,
_ => throw new InvalidOperationException($"Unsupported combined divisor square selector for digit {nMod10}."),
},
_ => throw new InvalidOperationException($"Unsupported combined divisor pattern for squares: {pattern}."),
};
private static ulong[] BuildCombinedDivisors(byte nMod10, CombinedDivisorPattern pattern, out ulong[] squares)
{
ReadOnlySpan<ulong> groupA = HeuristicPrimeSieves.GroupADivisors;
ReadOnlySpan<uint> groupB = GetGroupBDivisors(nMod10);
var combined = new List<ulong>(groupA.Length + groupB.Length);
int groupAIndex = 0;
while (groupAIndex < groupA.Length && groupA[groupAIndex] <= 19)
{
combined.Add(groupA[groupAIndex]);
groupAIndex++;
}
int groupBIndex = GetGroupBStartIndex(groupB);
int groupAInterleaveCount;
int groupBInterleaveCount;
switch (pattern)
{
case CombinedDivisorPattern.OneAOneB:
groupAInterleaveCount = 1;
groupBInterleaveCount = 1;
break;
case CombinedDivisorPattern.TwoAOneB:
groupAInterleaveCount = 2;
groupBInterleaveCount = 1;
break;
case CombinedDivisorPattern.ThreeAOneB:
groupAInterleaveCount = 3;
groupBInterleaveCount = 1;
break;
case CombinedDivisorPattern.ThreeATwoB:
groupAInterleaveCount = 3;
groupBInterleaveCount = 2;
break;
default:
groupAInterleaveCount = 2;
groupBInterleaveCount = 1;
break;
}
while (groupAIndex < groupA.Length || groupBIndex < groupB.Length)
{
int addedA = 0;
while (addedA < groupAInterleaveCount && groupAIndex < groupA.Length)
{
combined.Add(groupA[groupAIndex]);
groupAIndex++;
addedA++;
}
int addedB = 0;
while (addedB < groupBInterleaveCount && groupBIndex < groupB.Length)
{
combined.Add(groupB[groupBIndex]);
groupBIndex++;
addedB++;
}
}
ulong[] result = [.. combined];
ulong[] resultSquares = new ulong[result.Length];
for (int i = 0; i < result.Length; i++)
{
ulong divisor = result[i];
resultSquares[i] = divisor * divisor;
}
squares = resultSquares;
return result;
}
private static int GetGroupBStartIndex(ReadOnlySpan<uint> divisors)
{
int index = 0;
while (index < divisors.Length && IsGroupAPrefixValue(divisors[index]))
{
index++;
}
return index;
}
private static bool IsGroupAPrefixValue(ulong value) => value is 3UL or 7UL or 11UL or 13UL;
private static HeuristicDivisorGroup ResolveGroup(ulong value) => value switch
{
3UL or 7UL or 11UL or 13UL => HeuristicDivisorGroup.GroupAConstant,
_ when value % 10UL == 3UL => HeuristicDivisorGroup.GroupAWheel,
_ => HeuristicDivisorGroup.GroupB,
};
private static ReadOnlySpan<uint> GetGroupBDivisors(byte ending) => ending switch
{
1 => DivisorGenerator.SmallPrimesLastOneWithoutLastThree,
3 => [],
7 => DivisorGenerator.SmallPrimesLastSevenWithoutLastThree,
9 => DivisorGenerator.SmallPrimesLastNineWithoutLastThree,
_ => [],
};
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static HeuristicDivisorEnumerator CreateHeuristicDivisorEnumerator(ulong maxDivisorSquare, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
{
return new HeuristicDivisorEnumerator(maxDivisorSquare, nMod10, groupBBuffer);
}
internal struct HeuristicGroupBSequenceState
{
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static MersenneHeuristicDivisorEnumerator CreateMersenneDivisorEnumerator(ulong exponent, ulong maxDivisor)
{
return new MersenneHeuristicDivisorEnumerator(exponent, maxDivisor);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static HeuristicDivisorPreparation PrepareHeuristicDivisor(in HeuristicDivisorCandidate candidate)
{
ulong divisor = candidate.Value;
MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
bool hasCycleHint = TryGetCycleLengthHint(divisor, out ulong cycleLength);
return new HeuristicDivisorPreparation(candidate, divisorData, cycleLength, hasCycleHint);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static ulong ResolveHeuristicCycleLength(
PrimeOrderCalculatorAccelerator gpu,
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(
gpu,
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 maxDivisorSquare;
private readonly ReadOnlySpan<ulong> combinedDivisors;
private readonly ReadOnlySpan<ulong> combinedDivisorSquares;
private int index;
public HeuristicDivisorEnumerator(ulong maxDivisorSquare, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
{
this.maxDivisorSquare = maxDivisorSquare;
_ = groupBBuffer;
combinedDivisors = GetCombinedDivisors(nMod10);
combinedDivisorSquares = GetCombinedDivisorSquares(nMod10);
index = 0;
}
public bool TryGetNext(out HeuristicDivisorCandidate candidate)
{
while (index < combinedDivisors.Length)
{
int currentIndex = index;
ulong divisorSquare = combinedDivisorSquares[currentIndex];
if (divisorSquare > maxDivisorSquare)
{
index = combinedDivisors.Length;
break;
}
ulong entry = combinedDivisors[currentIndex];
index = currentIndex + 1;
HeuristicDivisorGroup group = ResolveGroup(entry);
ulong value = entry;
byte ending = (byte)(value % 10UL);
ushort residue = (ushort)(value % Wheel210);
candidate = new HeuristicDivisorCandidate(value, group, ending, 0, residue);
return true;
}
candidate = default;
return false;
}
}
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 readonly ulong ProcessedCount => processedCount;
public readonly ulong LastDivisor => lastDivisor;
public readonly 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);
}
}
}