586 lines
15 KiB
C#
586 lines
15 KiB
C#
using System.Numerics;
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using System.Runtime.CompilerServices;
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using System.Globalization;
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using PerfectNumbers.Core.Gpu;
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using PerfectNumbers.Core.Gpu.Accelerators;
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namespace PerfectNumbers.Core.Cpu;
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public struct MersenneNumberDivisorByDivisorCpuTesterWithCpuOrder() : IMersenneNumberDivisorByDivisorTester
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{
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public BigInteger DivisorLimit;
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public BigInteger MinK = EnvironmentConfiguration.MinK;
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#pragma warning disable CS8618 // StateFilePath is always set on EvenPerfectBitScanner execution path when ResumeFromState is called.
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private string StateFilePath;
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#pragma warning restore CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring as nullable.
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private int _stateCounter;
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private BigInteger _lastSavedK;
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private GpuUInt128WorkSet _divisorScanGpuWorkSet;
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public void ResetStateTracking()
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{
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_stateCounter = 0;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public void ResumeFromState(in string stateFile, in BigInteger lastSavedK, in BigInteger minK)
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{
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StateFilePath = stateFile;
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_lastSavedK = lastSavedK;
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MinK = minK;
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_stateCounter = 0;
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}
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public bool IsPrime(ulong prime, out bool divisorsExhausted, out BigInteger divisor)
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{
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BigInteger allowedMax = MersenneNumberDivisorByDivisorTester.ComputeAllowedMaxDivisorBig(prime, DivisorLimit);
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// The CPU by-divisor run always hands us primes with enormous divisor limits, so the fallback below never executes.
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// if (allowedMax < 3UL)
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// {
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// // EvenPerfectBitScanner routes primes below the small-divisor cutoff to the GPU path, so the CPU path still sees
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// // trivial candidates during targeted tests. Short-circuit here to keep those runs aligned with the production flow.
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// divisorsExhausted = true;
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// return true;
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// }
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bool composite = CheckDivisors(
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prime,
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allowedMax,
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MinK,
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out bool processedAll,
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out divisor);
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if (composite)
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{
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divisorsExhausted = true;
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return false;
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}
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divisorsExhausted = processedAll || composite;
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divisor = BigInteger.Zero;
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return true;
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}
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public void PrepareCandidates(ulong maxPrime, in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
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{
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BigInteger divisorLimitBigInteger = MersenneNumberDivisorByDivisorTester.ComputeDivisorLimitFromMaxPrimeBig(maxPrime);
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DivisorLimit = divisorLimitBigInteger;
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ulong divisorLimit = MersenneNumberDivisorByDivisorTester.GetAllowedDivisorLimitForSpan(divisorLimitBigInteger);
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int length = primes.Length;
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for (int index = 0; index < length; index++)
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{
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allowedMaxValues[index] = MersenneNumberDivisorByDivisorTester.ComputeAllowedMaxDivisor(primes[index], divisorLimit);
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}
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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public readonly IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession(PrimeOrderCalculatorAccelerator gpu) => new MersenneCpuDivisorScanSessionWithCpuOrder();
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private bool CheckDivisors(
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ulong prime,
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BigInteger allowedMax,
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BigInteger minK,
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out bool processedAll,
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out BigInteger foundDivisor)
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{
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BigInteger normalizedMinK = minK < BigInteger.One ? BigInteger.One : minK;
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BigInteger step = ((BigInteger)prime) << 1;
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BigInteger firstDivisor = (step * normalizedMinK) + BigInteger.One;
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bool unlimited = allowedMax.IsZero;
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bool fits64 = normalizedMinK <= ulong.MaxValue && firstDivisor <= ulong.MaxValue;
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bool limitFits64 = unlimited || allowedMax <= ulong.MaxValue;
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if (fits64 && limitFits64)
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{
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ulong allowedMax64 = unlimited ? ulong.MaxValue : (ulong)allowedMax;
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bool composite64 = CheckDivisors64Bit(
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prime,
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allowedMax64,
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(ulong)normalizedMinK,
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out processedAll,
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out ulong foundDivisor64);
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foundDivisor = foundDivisor64;
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return composite64;
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}
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if (fits64 && allowedMax > ulong.MaxValue)
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{
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ulong allowedMax64 = ulong.MaxValue;
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bool composite64 = CheckDivisors64Bit(
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prime,
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allowedMax64,
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(ulong)normalizedMinK,
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out processedAll,
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out ulong foundDivisor64);
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if (composite64)
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{
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foundDivisor = foundDivisor64;
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return true;
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}
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BigInteger iterations = ((BigInteger)(allowedMax64 - (ulong)firstDivisor) / (ulong)step) + BigInteger.One;
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BigInteger nextK = normalizedMinK + iterations;
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return CheckDivisorsLarge(
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prime,
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allowedMax,
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nextK,
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step,
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out processedAll,
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out foundDivisor);
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}
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return CheckDivisorsLarge(
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prime,
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allowedMax,
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normalizedMinK,
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step,
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out processedAll,
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out foundDivisor);
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}
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private bool CheckDivisors64Bit(
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ulong prime,
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ulong allowedMax,
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ulong minK,
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out bool processedAll,
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out ulong foundDivisor)
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{
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foundDivisor = 0UL;
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ulong currentK = minK < 1UL ? 1UL : minK;
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// The EvenPerfectBitScanner feeds primes >= 138,000,000 here, so allowedMax >= 3 in production runs.
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// Keeping the guard commented out documents the reasoning for benchmarks and tests.
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// if (allowedMax < 3UL)
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// {
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// return false;
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// }
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ref GpuUInt128WorkSet workSet = ref _divisorScanGpuWorkSet;
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ref GpuUInt128 step = ref workSet.Step;
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step.High = 0UL;
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step.Low = prime;
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step.ShiftLeft(1);
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ref GpuUInt128 limit = ref workSet.Limit;
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limit.High = 0UL;
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limit.Low = allowedMax;
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ref GpuUInt128 divisor = ref workSet.Divisor;
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divisor.High = step.High;
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divisor.Low = step.Low;
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divisor.Add(1UL);
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if (minK > 1UL)
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{
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GpuUInt128 offset = new(minK - 1UL);
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divisor = step * offset;
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divisor.Add(1UL);
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}
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if (divisor.CompareTo(limit) > 0)
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{
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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// Intentionally recomputes factorizations without a per-thread cache.
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// The previous factor cache recorded virtually no hits and only slowed down the scan.
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ulong stepHigh = step.High;
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ulong stepLow = step.Low;
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ulong limitHigh = limit.High;
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if (stepHigh == 0UL && limitHigh == 0UL)
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{
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ulong maxK = allowedMax > 0UL ? (allowedMax - 1UL) / stepLow : 0UL;
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if (maxK == 0UL)
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{
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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ulong startK = minK < 1UL ? 1UL : minK;
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bool processedTop = true;
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bool processedBottom = true;
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bool composite = false;
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if (startK <= maxK)
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{
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composite = CheckDivisors64Range(
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prime,
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stepLow,
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allowedMax,
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startK,
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maxK,
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ref currentK,
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out processedTop,
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out foundDivisor);
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if (composite)
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{
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processedAll = true;
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return true;
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}
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}
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ulong lowerEnd = startK > 1UL ? startK - 1UL : 0UL;
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if (lowerEnd >= 1UL && startK == 1UL)
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{
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lowerEnd = Math.Min(lowerEnd, maxK);
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currentK = 1UL;
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composite = CheckDivisors64Range(
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prime,
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stepLow,
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allowedMax,
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1UL,
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lowerEnd,
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ref currentK,
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out processedBottom,
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out foundDivisor);
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}
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processedAll = processedTop && processedBottom;
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return composite;
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}
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var residueStepper = new MersenneDivisorResidueStepper(prime, step, divisor);
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while (divisor.CompareTo(limit) <= 0)
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{
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if (residueStepper.IsAdmissible())
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{
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ulong candidate = divisor.Low;
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MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
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ulong divisorCycle;
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// Divisors generated from 2 * k * p + 1 exceed the small-cycle snapshot when p >= 138,000,000, so the short path below never runs.
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if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
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candidate,
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prime,
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divisorData,
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out ulong computedCycle,
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out bool primeOrderFailed) || computedCycle == 0UL)
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{
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// Divisors produced by 2 * k * p + 1 always exceed PerfectNumberConstants.MaxQForDivisorCycles
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// for the exponents scanned here, so skip the unused cache fallback and compute directly.
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divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
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candidate,
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divisorData,
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skipPrimeOrderHeuristic: primeOrderFailed);
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}
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else
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{
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divisorCycle = computedCycle;
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}
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RecordState(StateFilePath, currentK);
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if (divisorCycle == prime)
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{
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// A cycle equal to the tested exponent (which is prime in this path) guarantees that the candidate divides
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// the corresponding Mersenne number because the order of 2 modulo the divisor is exactly p.
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foundDivisor = candidate;
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processedAll = true;
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return true;
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}
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if (divisorCycle == 0UL)
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{
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Console.WriteLine($"Divisor cycle was not calculated for {prime}");
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}
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}
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divisor.Add(step);
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currentK++;
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residueStepper.Advance();
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}
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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private bool CheckDivisorsLarge(
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ulong prime,
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BigInteger allowedMax,
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BigInteger minK,
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BigInteger step,
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out bool processedAll,
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out BigInteger foundDivisor)
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{
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processedAll = true;
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foundDivisor = BigInteger.Zero;
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BigInteger currentK = minK < BigInteger.One ? BigInteger.One : minK;
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BigInteger divisor = (step * currentK) + BigInteger.One;
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if (allowedMax.IsZero)
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{
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processedAll = false;
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return false;
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}
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if (divisor > allowedMax)
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{
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return false;
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}
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LastDigit lastDigit = (prime & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
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ushort decimalMask = DivisorGenerator.GetDecimalMask(lastDigit);
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var rem10 = new BigIntegerCycleRemainderStepper(10);
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var rem8 = new BigIntegerCycleRemainderStepper(8);
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var rem5 = new BigIntegerCycleRemainderStepper(5);
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var rem3 = new BigIntegerCycleRemainderStepper(3);
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var rem7 = new BigIntegerCycleRemainderStepper(7);
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var rem11 = new BigIntegerCycleRemainderStepper(11);
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var rem13 = new BigIntegerCycleRemainderStepper(13);
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var rem17 = new BigIntegerCycleRemainderStepper(17);
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var rem19 = new BigIntegerCycleRemainderStepper(19);
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byte remainder10 = (byte)rem10.Initialize(divisor);
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byte remainder8 = (byte)rem8.Initialize(divisor);
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byte remainder5 = (byte)rem5.Initialize(divisor);
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byte remainder3 = (byte)rem3.Initialize(divisor);
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byte remainder7 = (byte)rem7.Initialize(divisor);
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byte remainder11 = (byte)rem11.Initialize(divisor);
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byte remainder13 = (byte)rem13.Initialize(divisor);
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byte remainder17 = (byte)rem17.Initialize(divisor);
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byte remainder19 = (byte)rem19.Initialize(divisor);
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while (divisor <= allowedMax)
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{
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bool passesSmallModuli = remainder3 != 0 && remainder5 != 0 && remainder7 != 0 && remainder11 != 0 && remainder13 != 0 && remainder17 != 0 && remainder19 != 0;
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if (passesSmallModuli && (remainder8 == 1 || remainder8 == 7) && ((decimalMask >> remainder10) & 1) != 0)
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{
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if (MersenneNumberDivisorByDivisorTester.IsProbablePrimeBigInteger(divisor))
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{
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BigInteger powResult = BigInteger.ModPow(2, prime, divisor);
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RecordState(StateFilePath, currentK);
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if (powResult.IsOne)
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{
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foundDivisor = divisor;
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processedAll = true;
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return true;
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}
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}
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else
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{
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RecordState(StateFilePath, currentK);
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}
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}
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currentK += BigInteger.One;
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divisor += step;
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remainder10 = (byte)rem10.ComputeNext(divisor);
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remainder8 = (byte)rem8.ComputeNext(divisor);
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remainder5 = (byte)rem5.ComputeNext(divisor);
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remainder3 = (byte)rem3.ComputeNext(divisor);
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remainder7 = (byte)rem7.ComputeNext(divisor);
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remainder11 = (byte)rem11.ComputeNext(divisor);
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remainder13 = (byte)rem13.ComputeNext(divisor);
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remainder17 = (byte)rem17.ComputeNext(divisor);
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remainder19 = (byte)rem19.ComputeNext(divisor);
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if (divisor > allowedMax)
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{
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break;
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}
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}
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processedAll = true;
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foundDivisor = BigInteger.Zero;
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return false;
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}
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private bool CheckDivisors64Range(
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ulong prime,
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ulong step,
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ulong allowedMax,
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ulong startK,
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ulong endK,
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ref ulong currentK,
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out bool processedAll,
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out ulong foundDivisor)
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{
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if (startK < 1UL || endK < startK)
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{
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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currentK = startK;
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UInt128 step128 = step;
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UInt128 allowedMax128 = allowedMax;
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UInt128 startDivisor128 = (step128 * startK) + UInt128.One;
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if (startDivisor128 > allowedMax128)
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{
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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UInt128 rangeLimit128 = (step128 * endK) + UInt128.One;
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if (rangeLimit128 > allowedMax128)
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{
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rangeLimit128 = allowedMax128;
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}
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ulong startDivisor = (ulong)startDivisor128;
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ulong rangeLimit = (ulong)rangeLimit128;
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var residueStepper = new MersenneDivisorResidueStepper(prime, (GpuUInt128)step128, (GpuUInt128)startDivisor128);
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return CheckDivisors64(
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prime,
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step,
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rangeLimit,
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startDivisor,
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ref residueStepper,
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ref currentK,
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out processedAll,
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out foundDivisor);
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}
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private bool CheckDivisors64(
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ulong prime,
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ulong step,
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ulong limit,
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ulong divisor,
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ref MersenneDivisorResidueStepper residueStepper,
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ref ulong currentK,
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out bool processedAll,
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out ulong foundDivisor)
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{
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bool canAdvance = step <= limit;
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if (!canAdvance)
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{
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if (divisor <= limit && residueStepper.IsAdmissible())
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{
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MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
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ulong divisorCycle;
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if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
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divisor,
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prime,
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divisorData,
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out ulong computedCycle,
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out bool primeOrderFailed) || computedCycle == 0UL)
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{
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divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
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divisor,
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divisorData,
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skipPrimeOrderHeuristic: primeOrderFailed);
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}
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else
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{
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divisorCycle = computedCycle;
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}
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if (divisorCycle == prime)
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{
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foundDivisor = divisor;
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processedAll = true;
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return true;
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}
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if (divisorCycle == 0UL)
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{
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Console.WriteLine($"Divisor cycle was not calculated for {prime}");
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}
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}
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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if (divisor > limit)
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{
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processedAll = true;
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foundDivisor = 0UL;
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return false;
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}
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ulong remainingIterations = ((limit - divisor) / step) + 1UL;
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while (true)
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{
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if (residueStepper.IsAdmissible())
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{
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MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
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ulong divisorCycle;
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if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
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divisor,
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prime,
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divisorData,
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out ulong computedCycle,
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out bool primeOrderFailed) || computedCycle == 0UL)
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{
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divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
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divisor,
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divisorData,
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skipPrimeOrderHeuristic: primeOrderFailed);
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}
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else
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{
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divisorCycle = computedCycle;
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}
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RecordState(StateFilePath, currentK);
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if (divisorCycle == prime)
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{
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foundDivisor = divisor;
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processedAll = true;
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return true;
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}
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if (divisorCycle == 0UL)
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{
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Console.WriteLine($"Divisor cycle was not calculated for {prime}");
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}
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}
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remainingIterations--;
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if (remainingIterations == 0UL)
|
|
{
|
|
processedAll = true;
|
|
foundDivisor = 0UL;
|
|
return false;
|
|
}
|
|
|
|
divisor += step;
|
|
currentK++;
|
|
residueStepper.Advance();
|
|
}
|
|
}
|
|
|
|
private void RecordState(in string path, BigInteger k)
|
|
{
|
|
|
|
if (k <= _lastSavedK)
|
|
{
|
|
return;
|
|
}
|
|
|
|
int next = _stateCounter + 1;
|
|
if (next >= PerfectNumberConstants.ByDivisorStateSaveInterval)
|
|
{
|
|
string? directory = Path.GetDirectoryName(path);
|
|
if (!string.IsNullOrEmpty(directory))
|
|
{
|
|
Directory.CreateDirectory(directory);
|
|
}
|
|
|
|
File.AppendAllText(path, k.ToString(CultureInfo.InvariantCulture) + Environment.NewLine);
|
|
_stateCounter = 0;
|
|
_lastSavedK = k;
|
|
}
|
|
else
|
|
{
|
|
_stateCounter = next;
|
|
}
|
|
}
|
|
}
|