MersenneNumberDivisorByDivisorCpuTesterWithCpuOrder, MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder & MersenneNumberDivisorByDivisorCpuTesterWithGpuOrder converted to device dependent template MersenneNumberDivisorByDivisorCpuTesterWithTemplate.

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTesterWithCpuOrder.cs

@@ -1,585 +0,0 @@
-using System.Numerics;
-using System.Runtime.CompilerServices;
-using System.Globalization;
-using PerfectNumbers.Core.Gpu;
-using PerfectNumbers.Core.Gpu.Accelerators;
-
-namespace PerfectNumbers.Core.Cpu;
-
-public struct MersenneNumberDivisorByDivisorCpuTesterWithCpuOrder() : IMersenneNumberDivisorByDivisorTester
-{
-	public BigInteger DivisorLimit;
-	public BigInteger MinK = EnvironmentConfiguration.MinK;
-
-#pragma warning disable CS8618 // StateFilePath is always set on EvenPerfectBitScanner execution path when ResumeFromState is called.
-	private string StateFilePath;
-#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.
-
-	private int _stateCounter;
-	private BigInteger _lastSavedK;
-
-	private GpuUInt128WorkSet _divisorScanGpuWorkSet;
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-	public void ResetStateTracking()
-	{
-		_stateCounter = 0;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-	public void ResumeFromState(in string stateFile, in BigInteger lastSavedK, in BigInteger minK)
-	{
-		StateFilePath = stateFile;
-		_lastSavedK = lastSavedK;
-		MinK = minK;
-		_stateCounter = 0;
-	}
-
-	public bool IsPrime(ulong prime, out bool divisorsExhausted, out BigInteger divisor)
-	{
-		BigInteger allowedMax = MersenneNumberDivisorByDivisorTester.ComputeAllowedMaxDivisorBig(prime, DivisorLimit);
-
-		// The CPU by-divisor run always hands us primes with enormous divisor limits, so the fallback below never executes.
-		// if (allowedMax < 3UL)
-		// {
-		//     // EvenPerfectBitScanner routes primes below the small-divisor cutoff to the GPU path, so the CPU path still sees
-		//     // trivial candidates during targeted tests. Short-circuit here to keep those runs aligned with the production flow.
-		//     divisorsExhausted = true;
-		//     return true;
-		// }
-
-
-		bool composite = CheckDivisors(
-			prime,
-			allowedMax,
-			MinK,
-			out bool processedAll,
-			out divisor);
-
-		if (composite)
-		{
-			divisorsExhausted = true;
-			return false;
-		}
-
-		divisorsExhausted = processedAll || composite;
-		divisor = BigInteger.Zero;
-		return true;
-	}
-
-	public void PrepareCandidates(ulong maxPrime, in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
-	{
-		BigInteger divisorLimitBigInteger = MersenneNumberDivisorByDivisorTester.ComputeDivisorLimitFromMaxPrimeBig(maxPrime);
-		DivisorLimit = divisorLimitBigInteger;
-		ulong divisorLimit = MersenneNumberDivisorByDivisorTester.GetAllowedDivisorLimitForSpan(divisorLimitBigInteger);
-		int length = primes.Length;
-		for (int index = 0; index < length; index++)
-		{
-			allowedMaxValues[index] = MersenneNumberDivisorByDivisorTester.ComputeAllowedMaxDivisor(primes[index], divisorLimit);
-		}
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-	public readonly IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession(PrimeOrderCalculatorAccelerator gpu) => new MersenneCpuDivisorScanSessionWithCpuOrder();
-
-	private bool CheckDivisors(
-		ulong prime,
-		BigInteger allowedMax,
-		BigInteger minK,
-		out bool processedAll,
-		out BigInteger foundDivisor)
-	{
-		BigInteger normalizedMinK = minK < BigInteger.One ? BigInteger.One : minK;
-		BigInteger step = ((BigInteger)prime) << 1;
-		BigInteger firstDivisor = (step * normalizedMinK) + BigInteger.One;
-		bool unlimited = allowedMax.IsZero;
-
-		bool fits64 = normalizedMinK <= ulong.MaxValue && firstDivisor <= ulong.MaxValue;
-		bool limitFits64 = unlimited || allowedMax <= ulong.MaxValue;
-		if (fits64 && limitFits64)
-		{
-			ulong allowedMax64 = unlimited ? ulong.MaxValue : (ulong)allowedMax;
-			bool composite64 = CheckDivisors64Bit(
-				prime,
-				allowedMax64,
-				(ulong)normalizedMinK,
-				out processedAll,
-				out ulong foundDivisor64);
-			foundDivisor = foundDivisor64;
-			return composite64;
-		}
-
-		if (fits64 && allowedMax > ulong.MaxValue)
-		{
-			ulong allowedMax64 = ulong.MaxValue;
-			bool composite64 = CheckDivisors64Bit(
-				prime,
-				allowedMax64,
-				(ulong)normalizedMinK,
-				out processedAll,
-				out ulong foundDivisor64);
-			if (composite64)
-			{
-				foundDivisor = foundDivisor64;
-				return true;
-			}
-
-			BigInteger iterations = ((BigInteger)(allowedMax64 - (ulong)firstDivisor) / (ulong)step) + BigInteger.One;
-			BigInteger nextK = normalizedMinK + iterations;
-			return CheckDivisorsLarge(
-				prime,
-				allowedMax,
-				nextK,
-				step,
-				out processedAll,
-				out foundDivisor);
-		}
-
-		return CheckDivisorsLarge(
-			prime,
-			allowedMax,
-			normalizedMinK,
-			step,
-			out processedAll,
-			out foundDivisor);
-	}
-
-	private bool CheckDivisors64Bit(
-		ulong prime,
-		ulong allowedMax,
-		ulong minK,
-		out bool processedAll,
-		out ulong foundDivisor)
-	{
-		foundDivisor = 0UL;
-		ulong currentK = minK < 1UL ? 1UL : minK;
-
-		// The EvenPerfectBitScanner feeds primes >= 138,000,000 here, so allowedMax >= 3 in production runs.
-		// Keeping the guard commented out documents the reasoning for benchmarks and tests.
-		// if (allowedMax < 3UL)
-		// {
-		//     return false;
-		// }
-
-		ref GpuUInt128WorkSet workSet = ref _divisorScanGpuWorkSet;
-
-		ref GpuUInt128 step = ref workSet.Step;
-		step.High = 0UL;
-		step.Low = prime;
-		step.ShiftLeft(1);
-
-		ref GpuUInt128 limit = ref workSet.Limit;
-		limit.High = 0UL;
-		limit.Low = allowedMax;
-
-		ref GpuUInt128 divisor = ref workSet.Divisor;
-		divisor.High = step.High;
-		divisor.Low = step.Low;
-		divisor.Add(1UL);
-		if (minK > 1UL)
-		{
-			GpuUInt128 offset = new(minK - 1UL);
-			divisor = step * offset;
-			divisor.Add(1UL);
-		}
-
-		if (divisor.CompareTo(limit) > 0)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		// Intentionally recomputes factorizations without a per-thread cache.
-		// The previous factor cache recorded virtually no hits and only slowed down the scan.
-
-		ulong stepHigh = step.High;
-		ulong stepLow = step.Low;
-		ulong limitHigh = limit.High;
-
-		if (stepHigh == 0UL && limitHigh == 0UL)
-		{
-			ulong maxK = allowedMax > 0UL ? (allowedMax - 1UL) / stepLow : 0UL;
-			if (maxK == 0UL)
-			{
-				processedAll = true;
-				foundDivisor = 0UL;
-				return false;
-			}
-
-			ulong startK = minK < 1UL ? 1UL : minK;
-			bool processedTop = true;
-			bool processedBottom = true;
-			bool composite = false;
-
-			if (startK <= maxK)
-			{
-				composite = CheckDivisors64Range(
-					prime,
-					stepLow,
-					allowedMax,
-					startK,
-					maxK,
-					ref currentK,
-					out processedTop,
-					out foundDivisor);
-				if (composite)
-				{
-					processedAll = true;
-					return true;
-				}
-			}
-
-			ulong lowerEnd = startK > 1UL ? startK - 1UL : 0UL;
-			if (lowerEnd >= 1UL && startK == 1UL)
-			{
-				lowerEnd = Math.Min(lowerEnd, maxK);
-				currentK = 1UL;
-				composite = CheckDivisors64Range(
-					prime,
-					stepLow,
-					allowedMax,
-					1UL,
-					lowerEnd,
-					ref currentK,
-					out processedBottom,
-					out foundDivisor);
-			}
-
-			processedAll = processedTop && processedBottom;
-			return composite;
-		}
-
-		var residueStepper = new MersenneDivisorResidueStepper(prime, step, divisor);
-
-		while (divisor.CompareTo(limit) <= 0)
-		{
-			if (residueStepper.IsAdmissible())
-			{
-				ulong candidate = divisor.Low;
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
-				ulong divisorCycle;
-				// Divisors generated from 2 * k * p + 1 exceed the small-cycle snapshot when p >= 138,000,000, so the short path below never runs.
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
-						candidate,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					// Divisors produced by 2 * k * p + 1 always exceed PerfectNumberConstants.MaxQForDivisorCycles
-					// for the exponents scanned here, so skip the unused cache fallback and compute directly.
-					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
-						candidate,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				RecordState(StateFilePath, currentK);
-				if (divisorCycle == prime)
-				{
-					// A cycle equal to the tested exponent (which is prime in this path) guarantees that the candidate divides
-					// the corresponding Mersenne number because the order of 2 modulo the divisor is exactly p.
-					foundDivisor = candidate;
-					processedAll = true;
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			divisor.Add(step);
-			currentK++;
-			residueStepper.Advance();
-		}
-
-		processedAll = true;
-		foundDivisor = 0UL;
-		return false;
-	}
-
-	private bool CheckDivisorsLarge(
-		ulong prime,
-		BigInteger allowedMax,
-		BigInteger minK,
-		BigInteger step,
-		out bool processedAll,
-		out BigInteger foundDivisor)
-	{
-		processedAll = true;
-		foundDivisor = BigInteger.Zero;
-		BigInteger currentK = minK < BigInteger.One ? BigInteger.One : minK;
-		BigInteger divisor = (step * currentK) + BigInteger.One;
-		if (allowedMax.IsZero)
-		{
-			processedAll = false;
-			return false;
-		}
-		if (divisor > allowedMax)
-		{
-			return false;
-		}
-
-		LastDigit lastDigit = (prime & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
-		ushort decimalMask = DivisorGenerator.GetDecimalMask(lastDigit);
-
-		var rem10 = new BigIntegerCycleRemainderStepper(10);
-		var rem8 = new BigIntegerCycleRemainderStepper(8);
-		var rem5 = new BigIntegerCycleRemainderStepper(5);
-		var rem3 = new BigIntegerCycleRemainderStepper(3);
-		var rem7 = new BigIntegerCycleRemainderStepper(7);
-		var rem11 = new BigIntegerCycleRemainderStepper(11);
-		var rem13 = new BigIntegerCycleRemainderStepper(13);
-		var rem17 = new BigIntegerCycleRemainderStepper(17);
-		var rem19 = new BigIntegerCycleRemainderStepper(19);
-
-		byte remainder10 = (byte)rem10.Initialize(divisor);
-		byte remainder8 = (byte)rem8.Initialize(divisor);
-		byte remainder5 = (byte)rem5.Initialize(divisor);
-		byte remainder3 = (byte)rem3.Initialize(divisor);
-		byte remainder7 = (byte)rem7.Initialize(divisor);
-		byte remainder11 = (byte)rem11.Initialize(divisor);
-		byte remainder13 = (byte)rem13.Initialize(divisor);
-		byte remainder17 = (byte)rem17.Initialize(divisor);
-		byte remainder19 = (byte)rem19.Initialize(divisor);
-
-		while (divisor <= allowedMax)
-		{
-			bool passesSmallModuli = remainder3 != 0 && remainder5 != 0 && remainder7 != 0 && remainder11 != 0 && remainder13 != 0 && remainder17 != 0 && remainder19 != 0;
-			if (passesSmallModuli && (remainder8 == 1 || remainder8 == 7) && ((decimalMask >> remainder10) & 1) != 0)
-			{
-				if (MersenneNumberDivisorByDivisorTester.IsProbablePrimeBigInteger(divisor))
-				{
-					BigInteger powResult = BigInteger.ModPow(2, prime, divisor);
-					RecordState(StateFilePath, currentK);
-					if (powResult.IsOne)
-					{
-						foundDivisor = divisor;
-						processedAll = true;
-						return true;
-					}
-				}
-				else
-				{
-					RecordState(StateFilePath, currentK);
-				}
-			}
-
-			currentK += BigInteger.One;
-			divisor += step;
-			remainder10 = (byte)rem10.ComputeNext(divisor);
-			remainder8 = (byte)rem8.ComputeNext(divisor);
-			remainder5 = (byte)rem5.ComputeNext(divisor);
-			remainder3 = (byte)rem3.ComputeNext(divisor);
-			remainder7 = (byte)rem7.ComputeNext(divisor);
-			remainder11 = (byte)rem11.ComputeNext(divisor);
-			remainder13 = (byte)rem13.ComputeNext(divisor);
-			remainder17 = (byte)rem17.ComputeNext(divisor);
-			remainder19 = (byte)rem19.ComputeNext(divisor);
-
-			if (divisor > allowedMax)
-			{
-				break;
-			}
-		}
-
-		processedAll = true;
-		foundDivisor = BigInteger.Zero;
-		return false;
-	}
-
-	private bool CheckDivisors64Range(
-		ulong prime,
-		ulong step,
-		ulong allowedMax,
-		ulong startK,
-		ulong endK,
-		ref ulong currentK,
-		out bool processedAll,
-		out ulong foundDivisor)
-	{
-		if (startK < 1UL || endK < startK)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-		currentK = startK;
-
-		UInt128 step128 = step;
-		UInt128 allowedMax128 = allowedMax;
-		UInt128 startDivisor128 = (step128 * startK) + UInt128.One;
-		if (startDivisor128 > allowedMax128)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		UInt128 rangeLimit128 = (step128 * endK) + UInt128.One;
-		if (rangeLimit128 > allowedMax128)
-		{
-			rangeLimit128 = allowedMax128;
-		}
-
-		ulong startDivisor = (ulong)startDivisor128;
-		ulong rangeLimit = (ulong)rangeLimit128;
-
-		var residueStepper = new MersenneDivisorResidueStepper(prime, (GpuUInt128)step128, (GpuUInt128)startDivisor128);
-
-		return CheckDivisors64(
-			prime,
-			step,
-			rangeLimit,
-			startDivisor,
-			ref residueStepper,
-			ref currentK,
-			out processedAll,
-			out foundDivisor);
-	}
-
-	private bool CheckDivisors64(
-			ulong prime,
-			ulong step,
-			ulong limit,
-			ulong divisor,
-			ref MersenneDivisorResidueStepper residueStepper,
-			ref ulong currentK,
-			out bool processedAll,
-			out ulong foundDivisor)
-	{
-		bool canAdvance = step <= limit;
-		if (!canAdvance)
-		{
-			if (divisor <= limit && residueStepper.IsAdmissible())
-			{
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
-						divisor,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
-						divisor,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				if (divisorCycle == prime)
-				{
-					foundDivisor = divisor;
-					processedAll = true;
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		if (divisor > limit)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		ulong remainingIterations = ((limit - divisor) / step) + 1UL;
-		while (true)
-		{
-			if (residueStepper.IsAdmissible())
-			{
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
-						divisor,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
-						divisor,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				RecordState(StateFilePath, currentK);
-				if (divisorCycle == prime)
-				{
-					foundDivisor = divisor;
-					processedAll = true;
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			remainingIterations--;
-			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;
-		}
-	}
-}

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTesterWithGpuOrder.cs

@@ -1,600 +0,0 @@
-using System.Numerics;
-using System.Runtime.CompilerServices;
-using System.Globalization;
-using PerfectNumbers.Core.Gpu;
-using PerfectNumbers.Core.Gpu.Accelerators;
-
-namespace PerfectNumbers.Core.Cpu;
-
-public struct MersenneNumberDivisorByDivisorCpuTesterWithGpuOrder() : IMersenneNumberDivisorByDivisorTester
-{
-	public BigInteger DivisorLimit;
-	public BigInteger MinK = EnvironmentConfiguration.MinK;
-	public readonly PrimeOrderCalculatorAccelerator Accelerator = PrimeOrderCalculatorAccelerator.Rent(1);
-
-#pragma warning disable CS8618 // StateFilePath is always set on EvenPerfectBitScanner execution path when ResumeFromState is called.
-	private string StateFilePath;
-#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.
-
-	private int _stateCounter;
-	private BigInteger _lastSavedK;
-
-	private GpuUInt128WorkSet _divisorScanGpuWorkSet;
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-	public void ResetStateTracking()
-	{
-		_stateCounter = 0;
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-	public void ResumeFromState(in string stateFile, in BigInteger lastSavedK, in BigInteger minK)
-	{
-		StateFilePath = stateFile;
-		_lastSavedK = lastSavedK;
-		MinK = minK;
-		_stateCounter = 0;
-	}
-
-	public bool IsPrime(ulong prime, out bool divisorsExhausted, out BigInteger divisor)
-	{
-		BigInteger allowedMax = MersenneNumberDivisorByDivisorTester.ComputeAllowedMaxDivisorBig(prime, DivisorLimit);
-
-		// The CPU by-divisor run always hands us primes with enormous divisor limits, so the fallback below never executes.
-		// if (allowedMax < 3UL)
-		// {
-		//     // EvenPerfectBitScanner routes primes below the small-divisor cutoff to the GPU path, so the CPU path still sees
-		//     // trivial candidates during targeted tests. Short-circuit here to keep those runs aligned with the production flow.
-		//     divisorsExhausted = true;
-		//     return true;
-		// }
-
-
-		bool composite = CheckDivisors(
-			prime,
-			allowedMax,
-			MinK,
-			out bool processedAll,
-			out divisor);
-
-		if (composite)
-		{
-			divisorsExhausted = true;
-			return false;
-		}
-
-		divisorsExhausted = processedAll || composite;
-		divisor = BigInteger.Zero;
-		return true;
-	}
-
-	public void PrepareCandidates(ulong maxPrime, in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
-	{
-		BigInteger divisorLimitBigInteger = MersenneNumberDivisorByDivisorTester.ComputeDivisorLimitFromMaxPrimeBig(maxPrime);
-		DivisorLimit = divisorLimitBigInteger;
-		ulong divisorLimit = MersenneNumberDivisorByDivisorTester.GetAllowedDivisorLimitForSpan(divisorLimitBigInteger);
-		int length = primes.Length;
-		for (int index = 0; index < length; index++)
-		{
-			allowedMaxValues[index] = MersenneNumberDivisorByDivisorTester.ComputeAllowedMaxDivisor(primes[index], divisorLimit);
-		}
-	}
-
-	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
-	public IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession(PrimeOrderCalculatorAccelerator gpu)
-	{
-		var session = new MersenneCpuDivisorScanSessionWithGpuOrder();
-		session.Configure(gpu);
-		return session;
-	}
-
-	private bool CheckDivisors(
-		ulong prime,
-		BigInteger allowedMax,
-		BigInteger minK,
-		out bool processedAll,
-		out BigInteger foundDivisor)
-	{
-		BigInteger normalizedMinK = minK < BigInteger.One ? BigInteger.One : minK;
-		BigInteger step = ((BigInteger)prime) << 1;
-		BigInteger firstDivisor = (step * normalizedMinK) + BigInteger.One;
-		bool unlimited = allowedMax.IsZero;
-
-		bool fits64 = normalizedMinK <= ulong.MaxValue && firstDivisor <= ulong.MaxValue;
-		bool limitFits64 = unlimited || allowedMax <= ulong.MaxValue;
-		if (fits64 && limitFits64)
-		{
-			ulong allowedMax64 = unlimited ? ulong.MaxValue : (ulong)allowedMax;
-			bool composite64 = CheckDivisors64Bit(
-				prime,
-				allowedMax64,
-				(ulong)normalizedMinK,
-				out processedAll,
-				out ulong foundDivisor64);
-			foundDivisor = foundDivisor64;
-			return composite64;
-		}
-
-		if (fits64 && allowedMax > ulong.MaxValue)
-		{
-			ulong allowedMax64 = ulong.MaxValue;
-			bool composite64 = CheckDivisors64Bit(
-				prime,
-				allowedMax64,
-				(ulong)normalizedMinK,
-				out processedAll,
-				out ulong foundDivisor64);
-			if (composite64)
-			{
-				foundDivisor = foundDivisor64;
-				return true;
-			}
-
-			BigInteger iterations = ((BigInteger)(allowedMax64 - (ulong)firstDivisor) / (ulong)step) + BigInteger.One;
-			BigInteger nextK = normalizedMinK + iterations;
-			return CheckDivisorsLarge(
-				prime,
-				allowedMax,
-				nextK,
-				step,
-				out processedAll,
-				out foundDivisor);
-		}
-
-		return CheckDivisorsLarge(
-			prime,
-			allowedMax,
-			normalizedMinK,
-			step,
-			out processedAll,
-			out foundDivisor);
-	}
-
-	private bool CheckDivisors64Bit(
-		ulong prime,
-		ulong allowedMax,
-		ulong minK,
-		out bool processedAll,
-		out ulong foundDivisor)
-	{
-		foundDivisor = 0UL;
-		ulong currentK = minK < 1UL ? 1UL : minK;
-
-		// The EvenPerfectBitScanner feeds primes >= 138,000,000 here, so allowedMax >= 3 in production runs.
-		// Keeping the guard commented out documents the reasoning for benchmarks and tests.
-		// if (allowedMax < 3UL)
-		// {
-		//     return false;
-		// }
-
-		ref GpuUInt128WorkSet workSet = ref _divisorScanGpuWorkSet;
-
-		ref GpuUInt128 step = ref workSet.Step;
-		step.High = 0UL;
-		step.Low = prime;
-		step.ShiftLeft(1);
-
-		ref GpuUInt128 limit = ref workSet.Limit;
-		limit.High = 0UL;
-		limit.Low = allowedMax;
-
-		ref GpuUInt128 divisor = ref workSet.Divisor;
-		divisor.High = step.High;
-		divisor.Low = step.Low;
-		divisor.Add(1UL);
-		if (minK > 1UL)
-		{
-			GpuUInt128 offset = new(minK - 1UL);
-			divisor = step * offset;
-			divisor.Add(1UL);
-		}
-
-		if (divisor.CompareTo(limit) > 0)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		// Intentionally recomputes factorizations without a per-thread cache.
-		// The previous factor cache recorded virtually no hits and only slowed down the scan.
-
-		ulong stepHigh = step.High;
-		ulong stepLow = step.Low;
-		ulong limitHigh = limit.High;
-
-		if (stepHigh == 0UL && limitHigh == 0UL)
-		{
-			ulong maxK = allowedMax > 0UL ? (allowedMax - 1UL) / stepLow : 0UL;
-			if (maxK == 0UL)
-			{
-				processedAll = true;
-				foundDivisor = 0UL;
-				return false;
-			}
-
-			ulong startK = minK < 1UL ? 1UL : minK;
-			bool processedTop = true;
-			bool processedBottom = true;
-			bool composite = false;
-
-			if (startK <= maxK)
-			{
-				composite = CheckDivisors64Range(
-					prime,
-					stepLow,
-					allowedMax,
-					startK,
-					maxK,
-					ref currentK,
-					out processedTop,
-					out foundDivisor);
-				if (composite)
-				{
-					processedAll = true;
-					return true;
-				}
-			}
-
-			ulong lowerEnd = startK > 1UL ? startK - 1UL : 0UL;
-			if (lowerEnd >= 1UL && startK == 1UL)
-			{
-				lowerEnd = Math.Min(lowerEnd, maxK);
-				currentK = 1UL;
-				composite = CheckDivisors64Range(
-					prime,
-					stepLow,
-					allowedMax,
-					1UL,
-					lowerEnd,
-					ref currentK,
-					out processedBottom,
-					out foundDivisor);
-			}
-
-			processedAll = processedTop && processedBottom;
-			return composite;
-		}
-
-		PrimeOrderCalculatorAccelerator gpu = Accelerator;
-		var residueStepper = new MersenneDivisorResidueStepper(prime, step, divisor);
-		while (divisor.CompareTo(limit) <= 0)
-		{
-			if (residueStepper.IsAdmissible())
-			{
-				ulong candidate = divisor.Low;
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
-				ulong divisorCycle;
-				// Divisors generated from 2 * k * p + 1 exceed the small-cycle snapshot when p >= 138,000,000, so the short path below never runs.
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentGpu(
-						candidate,
-						gpu,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					// Divisors produced by 2 * k * p + 1 always exceed PerfectNumberConstants.MaxQForDivisorCycles
-					// for the exponents scanned here, so skip the unused cache fallback and compute directly.
-					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthGpu(
-
-						candidate,
-						gpu,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				RecordState(currentK);
-				if (divisorCycle == prime)
-				{
-					// A cycle equal to the tested exponent (which is prime in this path) guarantees that the candidate divides
-					// the corresponding Mersenne number because the order of 2 modulo the divisor is exactly p.
-					foundDivisor = candidate;
-					processedAll = true;
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			divisor.Add(step);
-			currentK++;
-			residueStepper.Advance();
-		}
-
-		processedAll = true;
-		foundDivisor = 0UL;
-		return false;
-	}
-
-	private bool CheckDivisorsLarge(
-		ulong prime,
-		BigInteger allowedMax,
-		BigInteger minK,
-		BigInteger step,
-		out bool processedAll,
-		out BigInteger foundDivisor)
-	{
-		processedAll = true;
-		foundDivisor = BigInteger.Zero;
-		BigInteger currentK = minK < BigInteger.One ? BigInteger.One : minK;
-		BigInteger divisor = (step * currentK) + BigInteger.One;
-		if (allowedMax.IsZero)
-		{
-			processedAll = false;
-			return false;
-		}
-		if (divisor > allowedMax)
-		{
-			return false;
-		}
-
-		LastDigit lastDigit = (prime & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
-		ushort decimalMask = DivisorGenerator.GetDecimalMask(lastDigit);
-
-		var rem10 = new BigIntegerCycleRemainderStepper(10);
-		var rem8 = new BigIntegerCycleRemainderStepper(8);
-		var rem5 = new BigIntegerCycleRemainderStepper(5);
-		var rem3 = new BigIntegerCycleRemainderStepper(3);
-		var rem7 = new BigIntegerCycleRemainderStepper(7);
-		var rem11 = new BigIntegerCycleRemainderStepper(11);
-		var rem13 = new BigIntegerCycleRemainderStepper(13);
-		var rem17 = new BigIntegerCycleRemainderStepper(17);
-		var rem19 = new BigIntegerCycleRemainderStepper(19);
-
-		byte remainder10 = (byte)rem10.Initialize(divisor);
-		byte remainder8 = (byte)rem8.Initialize(divisor);
-		byte remainder5 = (byte)rem5.Initialize(divisor);
-		byte remainder3 = (byte)rem3.Initialize(divisor);
-		byte remainder7 = (byte)rem7.Initialize(divisor);
-		byte remainder11 = (byte)rem11.Initialize(divisor);
-		byte remainder13 = (byte)rem13.Initialize(divisor);
-		byte remainder17 = (byte)rem17.Initialize(divisor);
-		byte remainder19 = (byte)rem19.Initialize(divisor);
-
-		while (divisor <= allowedMax)
-		{
-			bool passesSmallModuli = remainder3 != 0 && remainder5 != 0 && remainder7 != 0 && remainder11 != 0 && remainder13 != 0 && remainder17 != 0 && remainder19 != 0;
-			if (passesSmallModuli && (remainder8 == 1 || remainder8 == 7) && ((decimalMask >> remainder10) & 1) != 0)
-			{
-				if (MersenneNumberDivisorByDivisorTester.IsProbablePrimeBigInteger(divisor))
-				{
-					BigInteger powResult = BigInteger.ModPow(2, prime, divisor);
-					RecordState(currentK);
-					if (powResult.IsOne)
-					{
-						foundDivisor = divisor;
-						processedAll = true;
-						return true;
-					}
-				}
-				else
-				{
-					RecordState(currentK);
-				}
-			}
-
-			currentK += BigInteger.One;
-			divisor += step;
-			remainder10 = (byte)rem10.ComputeNext(divisor);
-			remainder8 = (byte)rem8.ComputeNext(divisor);
-			remainder5 = (byte)rem5.ComputeNext(divisor);
-			remainder3 = (byte)rem3.ComputeNext(divisor);
-			remainder7 = (byte)rem7.ComputeNext(divisor);
-			remainder11 = (byte)rem11.ComputeNext(divisor);
-			remainder13 = (byte)rem13.ComputeNext(divisor);
-			remainder17 = (byte)rem17.ComputeNext(divisor);
-			remainder19 = (byte)rem19.ComputeNext(divisor);
-
-			if (divisor > allowedMax)
-			{
-				break;
-			}
-		}
-
-		processedAll = true;
-		foundDivisor = BigInteger.Zero;
-		return false;
-	}
-
-	private bool CheckDivisors64Range(
-		ulong prime,
-		ulong step,
-		ulong allowedMax,
-		ulong startK,
-		ulong endK,
-		ref ulong currentK,
-		out bool processedAll,
-		out ulong foundDivisor)
-	{
-		if (startK < 1UL || endK < startK)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-		currentK = startK;
-
-		UInt128 step128 = step;
-		UInt128 allowedMax128 = allowedMax;
-		UInt128 startDivisor128 = (step128 * startK) + UInt128.One;
-		if (startDivisor128 > allowedMax128)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		UInt128 rangeLimit128 = (step128 * endK) + UInt128.One;
-		if (rangeLimit128 > allowedMax128)
-		{
-			rangeLimit128 = allowedMax128;
-		}
-
-		ulong startDivisor = (ulong)startDivisor128;
-		ulong rangeLimit = (ulong)rangeLimit128;
-
-		var residueStepper = new MersenneDivisorResidueStepper(prime, (GpuUInt128)step128, (GpuUInt128)startDivisor128);
-
-		return CheckDivisors64(
-			prime,
-			step,
-			rangeLimit,
-			startDivisor,
-			ref residueStepper,
-			ref currentK,
-			out processedAll,
-			out foundDivisor);
-	}
-
-	private bool CheckDivisors64(
-			ulong prime,
-			ulong step,
-			ulong limit,
-			ulong divisor,
-			ref MersenneDivisorResidueStepper residueStepper,
-			ref ulong currentK,
-			out bool processedAll,
-			out ulong foundDivisor)
-	{
-		PrimeOrderCalculatorAccelerator gpu = Accelerator;
-
-		if (step > limit)
-		{
-			if (divisor <= limit && residueStepper.IsAdmissible())
-			{
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentGpu(
-						divisor,
-						gpu,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthGpu(
-						divisor,
-						gpu,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				if (divisorCycle == prime)
-				{
-					foundDivisor = divisor;
-					processedAll = true;
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		if (divisor > limit)
-		{
-			processedAll = true;
-			foundDivisor = 0UL;
-			return false;
-		}
-
-		ulong remainingIterations = ((limit - divisor) / step) + 1UL;
-		while (true)
-		{
-			if (residueStepper.IsAdmissible())
-			{
-				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentGpu(
-						divisor,
-						gpu,
-						prime,
-						divisorData,
-						out ulong computedCycle,
-						out bool primeOrderFailed) || computedCycle == 0UL)
-				{
-					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthGpu(
-						divisor,
-						gpu,
-						divisorData,
-						skipPrimeOrderHeuristic: primeOrderFailed);
-				}
-				else
-				{
-					divisorCycle = computedCycle;
-				}
-
-				RecordState(currentK);
-				if (divisorCycle == prime)
-				{
-					foundDivisor = divisor;
-					processedAll = true;
-					return true;
-				}
-
-				if (divisorCycle == 0UL)
-				{
-					Console.WriteLine($"Divisor cycle was not calculated for {prime}");
-				}
-			}
-
-			remainingIterations--;
-			if (remainingIterations == 0UL)
-			{
-				processedAll = true;
-				foundDivisor = 0UL;
-				return false;
-			}
-
-			divisor += step;
-			currentK++;
-			residueStepper.Advance();
-		}
-	}
-
-	private void RecordState(BigInteger k)
-	{
-		string path = StateFilePath;
-
-		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;
-		}
-	}
-}

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTesterWithTemplate.cs

@@ -6,11 +6,15 @@ using PerfectNumbers.Core.Gpu.Accelerators;
 
 namespace PerfectNumbers.Core.Cpu;
 
-public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersenneNumberDivisorByDivisorTester
+[DeviceDependentTemplate(typeof(ComputationDevice), suffix: "Order")]
+public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneNumberDivisorByDivisorTester
 {
 	public BigInteger DivisorLimit;
 	public BigInteger MinK = EnvironmentConfiguration.MinK;
+
+#if DEVICE_GPU || DEVICE_HYBRID
 	public readonly PrimeOrderCalculatorAccelerator Accelerator = PrimeOrderCalculatorAccelerator.Rent(1);
+#endif
 
 #pragma warning disable CS8618 // StateFilePath is always set on EvenPerfectBitScanner execution path when ResumeFromState is called.
 	private string StateFilePath;
@@ -21,11 +25,13 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 
 	private GpuUInt128WorkSet _divisorScanGpuWorkSet;
 
+	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 	public void ResetStateTracking()
 	{
 		_stateCounter = 0;
 	}
 
+	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 	public void ResumeFromState(in string stateFile, in BigInteger lastSavedK, in BigInteger minK)
 	{
 		StateFilePath = stateFile;
@@ -81,9 +87,17 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 	public readonly IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession(PrimeOrderCalculatorAccelerator gpu)
 	{
+#if DEVICE_GPU
+		var session = new MersenneCpuDivisorScanSessionWithGpuOrder();
+		session.Configure(gpu);
+		return session;
+#elif DEVICE_HYBRID
 		var session = new MersenneCpuDivisorScanSessionWithHybridOrder();
 		session.Configure(gpu);
 		return session;
+#else
+		return new MersenneCpuDivisorScanSessionWithCpuOrder();
+#endif
 	}
 
 	private bool CheckDivisors(
@@ -254,32 +268,69 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 			return composite;
 		}
 
+#if DEVICE_GPU || DEVICE_HYBRID
 		PrimeOrderCalculatorAccelerator gpu = Accelerator;
+#endif
 		var residueStepper = new MersenneDivisorResidueStepper(prime, step, divisor);
 
+		ulong computedCycle;
+		bool primeOrderFailed;
+		ulong candidate;
+		ulong divisorCycle;
+		bool computed;
 		while (divisor.CompareTo(limit) <= 0)
 		{
 			if (residueStepper.IsAdmissible())
 			{
-				ulong candidate = divisor.Low;
+				candidate = divisor.Low;
 				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(candidate);
-				ulong divisorCycle;
 				// Divisors generated from 2 * k * p + 1 exceed the small-cycle snapshot when p >= 138,000,000, so the short path below never runs.
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentHybrid(
+#if DEVICE_GPU
-						candidate,
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentGpu(
-						gpu,
+					candidate,
-						prime,
+					gpu,
-						divisorData,
+					prime,
-						out ulong computedCycle,
+					divisorData,
-						out bool primeOrderFailed) || computedCycle == 0UL)
+					out computedCycle,
+					out primeOrderFailed);
+#elif DEVICE_HYBRID
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentHybrid(
+					candidate,
+					gpu,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#else
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
+					candidate,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#endif
+				if (!computed || computedCycle == 0UL)
 				{
 					// Divisors produced by 2 * k * p + 1 always exceed PerfectNumberConstants.MaxQForDivisorCycles
 					// for the exponents scanned here, so skip the unused cache fallback and compute directly.
+#if DEVICE_GPU
+					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthGpu(
+						candidate,
+						gpu,
+						divisorData,
+						skipPrimeOrderHeuristic: primeOrderFailed);
+#elif DEVICE_HYBRID
 					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthHybrid(
 						candidate,
 						gpu,
 						divisorData,
 						skipPrimeOrderHeuristic: primeOrderFailed);
+#else
+					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
+						candidate,
+						divisorData,
+						skipPrimeOrderHeuristic: primeOrderFailed);
+#endif
 				}
 				else
 				{
@@ -312,6 +363,7 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 		return false;
 	}
 
+	[MethodImpl(MethodImplOptions.AggressiveOptimization)]
 	private bool CheckDivisorsLarge(
 		ulong prime,
 		BigInteger allowedMax,
@@ -402,6 +454,7 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 		return false;
 	}
 
+	[MethodImpl(MethodImplOptions.AggressiveOptimization)]
 	private bool CheckDivisors64Range(
 		ulong prime,
 		ulong step,
@@ -452,6 +505,7 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 			out foundDivisor);
 	}
 
+	[MethodImpl(MethodImplOptions.AggressiveOptimization)]
 	private bool CheckDivisors64(
 			ulong prime,
 			ulong step,
@@ -462,27 +516,63 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 			out bool processedAll,
 			out ulong foundDivisor)
 	{
+#if DEVICE_GPU || DEVICE_HYBRID
 		PrimeOrderCalculatorAccelerator gpu = Accelerator;
+#endif
+		ulong computedCycle;
+		bool primeOrderFailed;
 		bool canAdvance = step <= limit;
+		ulong divisorCycle;
+		bool computed;
 		if (!canAdvance)
 		{
 			if (divisor <= limit && residueStepper.IsAdmissible())
 			{
 				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
+#if DEVICE_GPU
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentHybrid(
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentGpu(
+					divisor,
+					gpu,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#elif DEVICE_HYBRID
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentHybrid(
+					divisor,
+					gpu,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#else
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
+					divisor,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#endif
+				if (!computed || computedCycle == 0UL)
+				{
+#if DEVICE_GPU
+					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthGpu(
 						divisor,
 						gpu,
-						prime,
 						divisorData,
-						out ulong computedCycle,
+						skipPrimeOrderHeuristic: primeOrderFailed);
-						out bool primeOrderFailed) || computedCycle == 0UL)
+#elif DEVICE_HYBRID
-				{
 					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthHybrid(
 						divisor,
 						gpu,
 						divisorData,
 						skipPrimeOrderHeuristic: primeOrderFailed);
+#else
+					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
+						divisor,
+						divisorData,
+						skipPrimeOrderHeuristic: primeOrderFailed);
+#endif
 				}
 				else
 				{
@@ -520,20 +610,50 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 			if (residueStepper.IsAdmissible())
 			{
 				MontgomeryDivisorData divisorData = MontgomeryDivisorData.FromModulus(divisor);
-				ulong divisorCycle;
+#if DEVICE_GPU
-				if (!MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentHybrid(
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentGpu(
+					divisor,
+					gpu,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#elif DEVICE_HYBRID
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentHybrid(
+					divisor,
+					gpu,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#else
+				computed = MersenneNumberDivisorByDivisorTester.TryCalculateCycleLengthForExponentCpu(
+					divisor,
+					prime,
+					divisorData,
+					out computedCycle,
+					out primeOrderFailed);
+#endif
+				if (!computed || computedCycle == 0UL)
+				{
+#if DEVICE_GPU
+					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthGpu(
 						divisor,
 						gpu,
-						prime,
 						divisorData,
-						out ulong computedCycle,
+						skipPrimeOrderHeuristic: primeOrderFailed);
-						out bool primeOrderFailed) || computedCycle == 0UL)
+#elif DEVICE_HYBRID
-				{
 					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthHybrid(
 						divisor,
 						gpu,
 						divisorData,
 						skipPrimeOrderHeuristic: primeOrderFailed);
+#else
+					divisorCycle = MersenneNumberDivisorByDivisorTester.CalculateCycleLengthCpu(
+						divisor,
+						divisorData,
+						skipPrimeOrderHeuristic: primeOrderFailed);
+#endif
 				}
 				else
 				{
@@ -568,10 +688,10 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithHybridOrder() : IMersen
 		}
 	}
 
+	[MethodImpl(MethodImplOptions.AggressiveOptimization)]
 	private void RecordState(BigInteger k)
 	{
 		string path = StateFilePath;
-
 		if (k <= _lastSavedK)
 		{
 			return;