--min-k command-line argument added. Partial factoring switched back to CPU.

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs

@@ -8,6 +8,7 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 {
 	private ulong _divisorLimit;
 	private int _batchSize = 1_024;
+	private ulong _minK = 1UL;
 
 	[ThreadStatic]
 	private static GpuUInt128WorkSet _divisorScanGpuWorkSet;
@@ -25,6 +26,12 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 		set => _batchSize = Math.Max(1, value);
 	}
 
+	public ulong MinK
+	{
+		get => _minK;
+		set => _minK = value < 1UL ? 1UL : value;
+	}
+
 	public void ConfigureFromMaxPrime(ulong maxPrime)
 	{
 		_divisorLimit = ComputeDivisorLimitFromMaxPrime(maxPrime);
@@ -61,6 +68,7 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 			gpu,
 			prime,
 			allowedMax,
+			_minK,
 			out processedAll,
 			out divisor);
 
@@ -100,9 +108,13 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 		PrimeOrderCalculatorAccelerator gpu,
 		ulong prime,
 		ulong allowedMax,
+		ulong minK,
 		out bool processedAll,
 		out ulong foundDivisor)
 	{
+		foundDivisor = 0UL;
+		processedAll = true;
+
 		// 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)
@@ -125,6 +137,13 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 		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;
@@ -165,31 +184,66 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 			step7 = (byte)(stepLow % 7UL);
 			step11 = (byte)(stepLow % 11UL);
 
-			remainder10 = (byte)(divisorLow % 10UL);
-			remainder8 = (byte)(divisorLow & 7UL);
-			remainder3 = (byte)(divisorLow % 3UL);
-			remainder7 = (byte)(divisorLow % 7UL);
-			remainder11 = (byte)(divisorLow % 11UL);
+			ulong maxK = allowedMax > 0UL ? (allowedMax - 1UL) / stepLow : 0UL;
+			if (maxK == 0UL)
+			{
+				processedAll = true;
+				foundDivisor = 0UL;
+				return false;
+			}
 
-			return CheckDivisors64(
-				gpu,
-				prime,
-				stepLow,
-				limit.Low,
-				divisorLow,
-				decimalMask,
-				step10,
-				step8,
-				step3,
-				step7,
-				step11,
-				remainder10,
-				remainder8,
-				remainder3,
-				remainder7,
-				remainder11,
-				out processedAll,
-				out foundDivisor);
+			ulong startK = minK < 1UL ? 1UL : minK;
+			bool processedTop = true;
+			bool processedBottom = true;
+			bool composite = false;
+
+			if (startK <= maxK)
+			{
+				composite = CheckDivisors64Range(
+					gpu,
+					prime,
+					stepLow,
+					allowedMax,
+					startK,
+					maxK,
+					decimalMask,
+					step10,
+					step8,
+					step3,
+					step7,
+					step11,
+					out processedTop,
+					out foundDivisor);
+				if (composite)
+				{
+					processedAll = true;
+					return true;
+				}
+			}
+
+			ulong lowerEnd = startK > 1UL ? startK - 1UL : 0UL;
+			if (lowerEnd >= 1UL)
+			{
+				lowerEnd = Math.Min(lowerEnd, maxK);
+				composite = CheckDivisors64Range(
+					gpu,
+					prime,
+					stepLow,
+					allowedMax,
+					1UL,
+					lowerEnd,
+					decimalMask,
+					step10,
+					step8,
+					step3,
+					step7,
+					step11,
+					out processedBottom,
+					out foundDivisor);
+			}
+
+			processedAll = processedTop && processedBottom;
+			return composite;
 		}
 
 		ulong divisorHigh = divisor.High;
@@ -265,6 +319,75 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester() : IMersenneNumberD
 		return false;
 	}
 
+	private static bool CheckDivisors64Range(
+		PrimeOrderCalculatorAccelerator gpu,
+		ulong prime,
+		ulong step,
+		ulong allowedMax,
+		ulong startK,
+		ulong endK,
+		ushort decimalMask,
+		byte step10,
+		byte step8,
+		byte step3,
+		byte step7,
+		byte step11,
+		out bool processedAll,
+		out ulong foundDivisor)
+	{
+		if (startK < 1UL || endK < startK)
+		{
+			processedAll = true;
+			foundDivisor = 0UL;
+			return false;
+		}
+
+		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;
+
+		byte remainder10 = (byte)(startDivisor % 10UL);
+		byte remainder8 = (byte)(startDivisor & 7UL);
+		byte remainder3 = (byte)(startDivisor % 3UL);
+		byte remainder7 = (byte)(startDivisor % 7UL);
+		byte remainder11 = (byte)(startDivisor % 11UL);
+
+		return CheckDivisors64(
+			gpu,
+			prime,
+			step,
+			rangeLimit,
+			startDivisor,
+			decimalMask,
+			step10,
+			step8,
+			step3,
+			step7,
+			step11,
+			remainder10,
+			remainder8,
+			remainder3,
+			remainder7,
+			remainder11,
+			out processedAll,
+			out foundDivisor);
+	}
+
 	private static bool CheckDivisors64(
 		PrimeOrderCalculatorAccelerator gpu,
 		ulong prime,

PerfectNumbers.Core/Gpu/AcceleratorPool.cs

@@ -1,9 +1,10 @@
 using ILGPU;
 using ILGPU.Runtime;
+using Open.Collections;
 
 namespace PerfectNumbers.Core.Gpu
 {
-	public struct AcceleratorPool
+	public struct AcceleratorPool : IDisposable
 	{
 		internal readonly Context Context;
 		internal readonly Device Device;
@@ -28,6 +29,23 @@ namespace PerfectNumbers.Core.Gpu
 			// Intentionally left empty - there's nothing to do here. We're not really renting anything.
 		}
 
+		public readonly void Dispose()
+		{
+			Accelerator[] accelerators = Accelerators;
+			HashSet<Context> contexts = new(accelerators.Length);
+			foreach (var accelerator in accelerators)
+			{
+				contexts.Add(accelerator.Context);
+				accelerator.Synchronize();
+				accelerator.Dispose();
+			}
+
+			foreach (var context in contexts)
+			{
+				context.Dispose();
+			}
+		}
+
 		public static readonly AcceleratorPool Shared = new(PerfectNumberConstants.RollingAccelerators);
 
 		private readonly int Capacity;

PerfectNumbers.Core/Gpu/Accelerators/PrimeOrderCalculatorAccelerator.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using System.Runtime.CompilerServices;
 using ILGPU;
 using ILGPU.Runtime;
@@ -9,8 +10,8 @@ public sealed class PrimeOrderCalculatorAccelerator
 {
 	#region Pool
 
-	[ThreadStatic]
-	private static Queue<PrimeOrderCalculatorAccelerator>? _pool;
+	// [ThreadStatic]
+	private static ConcurrentQueue<PrimeOrderCalculatorAccelerator>? _pool;
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
 	public static PrimeOrderCalculatorAccelerator Rent(int primeTesterCapacity)
@@ -34,7 +35,7 @@ public sealed class PrimeOrderCalculatorAccelerator
 
 	internal static void Clear()
 	{
-		Queue<PrimeOrderCalculatorAccelerator>? pool = _pool;
+		var pool = _pool;
 		if (pool != null)
 		{
 			while (pool.TryDequeue(out var gpu))
@@ -46,7 +47,7 @@ public sealed class PrimeOrderCalculatorAccelerator
 
 	internal static void DisposeAll()
 	{
-		Queue<PrimeOrderCalculatorAccelerator>? pool = _pool;
+		var pool = _pool;
 		if (pool != null)
 		{
 			while (pool.TryDequeue(out var gpu))
@@ -152,7 +153,7 @@ public sealed class PrimeOrderCalculatorAccelerator
 
 	private sealed class CalculatorKernels(Accelerator accelerator)
 	{
-		public readonly Action<AcceleratorStream, Index1D, ulong, CalculateOrderKernelConfig, ulong, ulong, ulong, ulong, ulong, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, OrderKernelBuffers> CalculateOrderKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, CalculateOrderKernelConfig, ulong, ulong, ulong, ulong, ulong, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, OrderKernelBuffers>(PrimeOrderKernels.CalculateOrderKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, CalculateOrderKernelConfig, ulong, ulong, ulong, ulong, ulong, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, OrderKernelBuffers>>();
+		// public readonly Action<AcceleratorStream, Index1D, ulong, CalculateOrderKernelConfig, ulong, ulong, ulong, ulong, ulong, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, OrderKernelBuffers> CalculateOrderKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, CalculateOrderKernelConfig, ulong, ulong, ulong, ulong, ulong, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, OrderKernelBuffers>(PrimeOrderKernels.CalculateOrderKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, CalculateOrderKernelConfig, ulong, ulong, ulong, ulong, ulong, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, OrderKernelBuffers>>();
 
 		public readonly Kernel CheckFactorsKernel = KernelUtil.GetKernel(accelerator.LoadStreamKernel<int, ulong, ArrayView1D<KeyValuePair<ulong, int>, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>>(PrimeOrderKernels.CheckFactorsKernel));
 
@@ -162,15 +163,15 @@ public sealed class PrimeOrderCalculatorAccelerator
 
 		public readonly Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>> KeepMontgomeryKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>>(Pow2MontgomeryKernels.Pow2MontgomeryKernelKeepMontgomery)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>>>();
 
-		public readonly Action<AcceleratorStream, Index1D, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, int, ulong, uint, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>> PartialFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, int, ulong, uint, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>(PrimeOrderKernels.PartialFactorKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, int, ulong, uint, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>>();
+		// public readonly Action<AcceleratorStream, Index1D, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, int, ulong, uint, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>> PartialFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, int, ulong, uint, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>(PrimeOrderKernels.PartialFactorKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, int, ulong, uint, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>>>();
 
-		public readonly Kernel PollardRhoKernel = KernelUtil.GetKernel(accelerator.LoadStreamKernel<ulong, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2MontgomeryKernels.TryPollardRhoKernel));
+		// public readonly Kernel PollardRhoKernel = KernelUtil.GetKernel(accelerator.LoadStreamKernel<ulong, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<byte, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(Pow2MontgomeryKernels.TryPollardRhoKernel));
 
 		public readonly Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>> Pow2ModKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<ulong, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>>(PrimeOrderKernels.Pow2ModKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<ulong, Stride1D.Dense>, ulong, ulong, ulong, ulong, ulong, ArrayView1D<ulong, Stride1D.Dense>>>();
 
 		public readonly Action<AcceleratorStream, Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>> Pow2ModWideKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>>(PrimeOrderKernels.Pow2ModKernelWide)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>>>();
 
-		public readonly Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<byte>> SharesFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<byte>>(PrimeTesterKernels.SharesFactorKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<byte>>>();
+		// public readonly Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<byte>> SharesFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ArrayView<ulong>, ArrayView<byte>>(PrimeTesterKernels.SharesFactorKernel)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ArrayView<ulong>, ArrayView<byte>>>();
 
 		public readonly Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>> SmallPrimeFactorKernelLauncher = KernelUtil.GetKernel(accelerator.LoadAutoGroupedStreamKernel<Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>(SmallPrimeFactorKernels.SmallPrimeFactorKernelScan)).CreateLauncherDelegate<Action<AcceleratorStream, Index1D, ulong, uint, ArrayView1D<uint, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>, int, ArrayView1D<ulong, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<int, Stride1D.Dense>, ArrayView1D<ulong, Stride1D.Dense>>>();
 
@@ -437,16 +438,16 @@ public sealed class PrimeOrderCalculatorAccelerator
 
 			var kernels = _kernels[acceleratorIndex];
 
-			CalculateOrderKernelLauncher = kernels.CalculateOrderKernelLauncher;
+			// CalculateOrderKernelLauncher = kernels.CalculateOrderKernelLauncher;
 			CheckFactorsKernel = kernels.CheckFactorsKernel;
 			ConvertToStandardKernelLauncher = kernels.ConvertToStandardKernelLauncher;
 			HeuristicCombinedTrialDivisionKernelLauncher = kernels.HeuristicCombinedTrialDivisionKernelLauncher;
 			KeepMontgomeryKernelLauncher = kernels.KeepMontgomeryKernelLauncher;
-			PartialFactorKernelLauncher = kernels.PartialFactorKernelLauncher;
-			PollardRhoKernel = kernels.PollardRhoKernel;
+			// PartialFactorKernelLauncher = kernels.PartialFactorKernelLauncher;
+			// PollardRhoKernel = kernels.PollardRhoKernel;
 			Pow2ModKernelLauncher = kernels.Pow2ModKernelLauncher;
 			Pow2ModWideKernelLauncher = kernels.Pow2ModWideKernelLauncher;
-			SharesFactorKernelLauncher = kernels.SharesFactorKernelLauncher;
+			// SharesFactorKernelLauncher = kernels.SharesFactorKernelLauncher;
 			SmallPrimeFactorKernelLauncher = kernels.SmallPrimeFactorKernelLauncher;
 			SmallPrimeSieveKernelLauncher = kernels.SmallPrimeSieveKernelLauncher;
 			SpecialMaxKernelLauncher = kernels.SpecialMaxKernelLauncher;

PerfectNumbers.Core/Gpu/MersenneNumberDivisorByDivisorGpuTester.cs

@@ -18,6 +18,7 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 	// so the synchronization fields from the previous implementation remain commented out here.
 	// private readonly object _sync = new();
 	private ulong _divisorLimit;
+	private ulong _minK = 1UL;
 	// private bool _isConfigured;
 
 	private readonly ConcurrentBag<MersenneNumberDivisorByDivisorAccelerator>[] _resourcePool = [.. AcceleratorPool.Shared.Accelerators.Select(x => new ConcurrentBag<MersenneNumberDivisorByDivisorAccelerator>())];
@@ -36,6 +37,12 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		set => GpuBatchSize = value;
 	}
 
+	public ulong MinK
+	{
+		get => _minK;
+		set => _minK = value < 1UL ? 1UL : value;
+	}
+
 	public void ConfigureFromMaxPrime(ulong maxPrime)
 	{
 		// EvenPerfectBitScanner configures the GPU tester once before scanning and never mutates the configuration afterwards,
@@ -95,6 +102,7 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 			gpu,
 			prime,
 			allowedMax,
+			_minK,
 			resources.CheckDivisorKernel,
 			resources.DivisorDataBuffer,
 			resources.OffsetBuffer,
@@ -162,6 +170,7 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		PrimeOrderCalculatorAccelerator gpu,
 		ulong prime,
 		ulong allowedMax,
+		ulong minK,
 		Kernel kernel,
 		MemoryBuffer1D<GpuDivisorPartialData, Stride1D.Dense> divisorDataBuffer,
 		MemoryBuffer1D<int, Stride1D.Dense> offsetBuffer,
@@ -183,8 +192,8 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		int batchCapacity = (int)divisorDataBuffer.Length;
 		bool composite = false;
 		bool processedAll;
-		processedCount = 0UL;
-		lastProcessed = 0UL;
+		ulong processedCountLocal = 0UL;
+		ulong lastProcessedLocal = 0UL;
 		var acceleratorIndex = gpu.AcceleratorIndex;
 
 		// EvenPerfectBitScanner always configures non-empty GPU divisor buffers, so the defensive guard stays
@@ -208,11 +217,13 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		if (!hasCandidates)
 		{
 			coveredRange = true;
+			processedCount = processedCountLocal;
+			lastProcessed = lastProcessedLocal;
 			return false;
 		}
 
 		ulong maxK = maxK128 > ulong.MaxValue ? ulong.MaxValue : (ulong)maxK128;
-		ulong remainingCount = maxK;
+		ulong startK = minK < 1UL ? 1UL : minK;
 
 		ulong stepValue = (ulong)twoP128;
 		byte step10 = (byte)(stepValue % 10UL);
@@ -221,13 +232,6 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		byte step7 = (byte)(stepValue % 7UL);
 		byte step11 = (byte)(stepValue % 11UL);
 
-		UInt128 currentDivisor128 = firstDivisor128;
-		ulong currentDivisorValue = (ulong)currentDivisor128;
-		byte remainder10 = (byte)(currentDivisorValue % 10UL);
-		byte remainder8 = (byte)(currentDivisorValue & 7UL);
-		byte remainder3 = (byte)(currentDivisorValue % 3UL);
-		byte remainder7 = (byte)(currentDivisorValue % 7UL);
-		byte remainder11 = (byte)(currentDivisorValue % 11UL);
 		LastDigit lastDigit = (prime & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
 		ushort decimalMask = DivisorGenerator.GetDecimalMask(lastDigit);
 
@@ -243,11 +247,6 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		Span<int> offsetSpan = offsetStorage;
 		Span<int> countSpan = countStorage;
 		Span<ulong> cycleSpan = cycleStorage;
-		ref GpuDivisorPartialData divisorDataRef = ref MemoryMarshal.GetReference(divisorDataSpan);
-		ref int offsetRef = ref MemoryMarshal.GetReference(offsetSpan);
-		ref int countRef = ref MemoryMarshal.GetReference(countSpan);
-		ref ulong cycleRef = ref MemoryMarshal.GetReference(cycleSpan);
-		ref ulong exponentRef = ref MemoryMarshal.GetReference(exponentSpan);
 
 		ArrayView1D<GpuDivisorPartialData, Stride1D.Dense> divisorDataView = divisorDataBuffer.View;
 		ArrayView1D<int, Stride1D.Dense> offsetView = offsetBuffer.View;
@@ -257,100 +256,258 @@ public sealed partial class MersenneNumberDivisorByDivisorGpuTester : IMersenneN
 		ArrayView1D<byte, Stride1D.Dense> hitsView = hitsBuffer.View;
 		ArrayView1D<int, Stride1D.Dense> hitIndexView = hitIndexBuffer.View;
 		Queue<MontgomeryDivisorData> divisorPool = MontgomeryDivisorDataPool.Shared;
-		while (remainingCount > 0UL && !composite)
+		static bool ProcessRange(
+			PrimeOrderCalculatorAccelerator gpu,
+			ulong prime,
+			UInt128 twoP128,
+			UInt128 allowedMax128,
+			byte step10,
+			byte step8,
+			byte step3,
+			byte step7,
+			byte step11,
+			ushort decimalMask,
+			ArrayView1D<GpuDivisorPartialData, Stride1D.Dense> divisorDataView,
+			ArrayView1D<int, Stride1D.Dense> offsetView,
+			ArrayView1D<int, Stride1D.Dense> countView,
+			ArrayView1D<ulong, Stride1D.Dense> cycleView,
+			ArrayView1D<ulong, Stride1D.Dense> exponentViewDevice,
+			ArrayView1D<byte, Stride1D.Dense> hitsView,
+			ArrayView1D<int, Stride1D.Dense> hitIndexView,
+			Span<ulong> divisorSpan,
+			Span<ulong> exponentSpan,
+			Span<GpuDivisorPartialData> divisorDataSpan,
+			Span<int> offsetSpan,
+			Span<int> countSpan,
+			Span<ulong> cycleSpan,
+			Queue<MontgomeryDivisorData> divisorPool,
+			int chunkCountBaseline,
+			int acceleratorIndex,
+			ref bool composite,
+			ref ulong processedCountLocal,
+			ref ulong lastProcessedLocal,
+			ulong rangeStartK,
+			ulong rangeEndK,
+			Kernel kernel)
 		{
-			int chunkCount = chunkCountBaseline;
-			if ((ulong)chunkCount > remainingCount)
+			if (rangeStartK < 1UL || rangeEndK < rangeStartK)
 			{
-				chunkCount = (int)remainingCount;
+				return true;
 			}
 
-			UInt128 nextDivisor128 = currentDivisor128;
-			int admissibleCount = 0;
-
-			byte localRemainder10 = remainder10;
-			byte localRemainder8 = remainder8;
-			byte localRemainder3 = remainder3;
-			byte localRemainder7 = remainder7;
-			byte localRemainder11 = remainder11;
-
-			for (int i = 0; i < chunkCount; i++)
+			UInt128 startDivisor128 = (twoP128 * rangeStartK) + UInt128.One;
+			if (startDivisor128 > allowedMax128)
 			{
-				bool passesSmallModuli = localRemainder3 != 0 && localRemainder7 != 0 && localRemainder11 != 0;
-				if (passesSmallModuli && (localRemainder8 == 1 || localRemainder8 == 7) && ((decimalMask >> localRemainder10) & 1) != 0)
-				{
-					ulong divisorValue = (ulong)nextDivisor128;
-					MontgomeryDivisorData montgomeryData = divisorPool.FromModulus(divisorValue);
-					ulong divisorCycle = ResolveDivisorCycle(gpu, divisorValue, prime, in montgomeryData);
-					if (divisorCycle == prime)
-					{
-						processedCount += (ulong)(i + 1);
-						lastProcessed = divisorValue;
-						coveredRange = true;
-						return true;
-					}
+				return true;
+			}
 
-					divisorPool.Return(montgomeryData);
-					divisorSpan[admissibleCount] = divisorValue;
-					divisorDataSpan[admissibleCount] = new GpuDivisorPartialData(divisorValue);
-					offsetSpan[admissibleCount] = admissibleCount;
-					countSpan[admissibleCount] = 1;
-					cycleSpan[admissibleCount] = divisorCycle;
-					exponentSpan[admissibleCount] = prime;
-					admissibleCount++;
+			UInt128 rangeLimit128 = (twoP128 * rangeEndK) + UInt128.One;
+			if (rangeLimit128 > allowedMax128)
+			{
+				rangeLimit128 = allowedMax128;
+			}
+
+			UInt128 rangeCount128 = ((rangeLimit128 - startDivisor128) / twoP128) + UInt128.One;
+			ulong rangeRemaining = rangeCount128 > ulong.MaxValue ? ulong.MaxValue : (ulong)rangeCount128;
+			UInt128 currentRangeDivisor128 = startDivisor128;
+			ulong currentRangeDivisorValue = (ulong)currentRangeDivisor128;
+			byte rangeRemainder10 = (byte)(currentRangeDivisorValue % 10UL);
+			byte rangeRemainder8 = (byte)(currentRangeDivisorValue & 7UL);
+			byte rangeRemainder3 = (byte)(currentRangeDivisorValue % 3UL);
+			byte rangeRemainder7 = (byte)(currentRangeDivisorValue % 7UL);
+			byte rangeRemainder11 = (byte)(currentRangeDivisorValue % 11UL);
+
+			while (rangeRemaining > 0UL && !composite)
+			{
+				int chunkCount = chunkCountBaseline;
+				if ((ulong)chunkCount > rangeRemaining)
+				{
+					chunkCount = (int)rangeRemaining;
 				}
 
-				nextDivisor128 += twoP128;
-				localRemainder10 = AddMod10(localRemainder10, step10);
-				localRemainder8 = AddMod8(localRemainder8, step8);
-				localRemainder3 = AddMod3(localRemainder3, step3);
-				localRemainder7 = AddMod7(localRemainder7, step7);
-				localRemainder11 = AddMod11(localRemainder11, step11);
+				UInt128 nextDivisor128 = currentRangeDivisor128;
+				int admissibleCount = 0;
+
+				byte localRemainder10 = rangeRemainder10;
+				byte localRemainder8 = rangeRemainder8;
+				byte localRemainder3 = rangeRemainder3;
+				byte localRemainder7 = rangeRemainder7;
+				byte localRemainder11 = rangeRemainder11;
+
+				for (int i = 0; i < chunkCount; i++)
+				{
+					bool passesSmallModuli = localRemainder3 != 0 && localRemainder7 != 0 && localRemainder11 != 0;
+					if (passesSmallModuli && (localRemainder8 == 1 || localRemainder8 == 7) && ((decimalMask >> localRemainder10) & 1) != 0)
+					{
+						ulong divisorValue = (ulong)nextDivisor128;
+						MontgomeryDivisorData montgomeryData = divisorPool.FromModulus(divisorValue);
+						ulong divisorCycle = ResolveDivisorCycle(gpu, divisorValue, prime, in montgomeryData);
+						if (divisorCycle == prime)
+						{
+							processedCountLocal += (ulong)(i + 1);
+							lastProcessedLocal = divisorValue;
+							composite = true;
+							return false;
+						}
+
+						divisorPool.Return(montgomeryData);
+						divisorSpan[admissibleCount] = divisorValue;
+						divisorDataSpan[admissibleCount] = new GpuDivisorPartialData(divisorValue);
+						offsetSpan[admissibleCount] = admissibleCount;
+						countSpan[admissibleCount] = 1;
+						cycleSpan[admissibleCount] = divisorCycle;
+						exponentSpan[admissibleCount] = prime;
+						admissibleCount++;
+					}
+
+					nextDivisor128 += twoP128;
+					localRemainder10 = AddMod10(localRemainder10, step10);
+					localRemainder8 = AddMod8(localRemainder8, step8);
+					localRemainder3 = AddMod3(localRemainder3, step3);
+					localRemainder7 = AddMod7(localRemainder7, step7);
+					localRemainder11 = AddMod11(localRemainder11, step11);
+				}
+
+				rangeRemainder10 = localRemainder10;
+				rangeRemainder8 = localRemainder8;
+				rangeRemainder3 = localRemainder3;
+				rangeRemainder7 = localRemainder7;
+				rangeRemainder11 = localRemainder11;
+
+				processedCountLocal += (ulong)chunkCount;
+
+				UInt128 lastDivisor128 = nextDivisor128 - twoP128;
+				lastProcessedLocal = (ulong)lastDivisor128;
+				currentRangeDivisor128 = nextDivisor128;
+				rangeRemaining -= (ulong)chunkCount;
+
+				if (admissibleCount == 0)
+				{
+					continue;
+				}
+
+				ref GpuDivisorPartialData divisorDataRef = ref MemoryMarshal.GetReference(divisorDataSpan);
+				ref int offsetRef = ref MemoryMarshal.GetReference(offsetSpan);
+				ref int countRef = ref MemoryMarshal.GetReference(countSpan);
+				ref ulong cycleRef = ref MemoryMarshal.GetReference(cycleSpan);
+				ref ulong exponentRef = ref MemoryMarshal.GetReference(exponentSpan);
+
+				var stream = AcceleratorStreamPool.Rent(acceleratorIndex);
+				divisorDataView.CopyFromCPU(stream, ref divisorDataRef, admissibleCount);
+				offsetView.CopyFromCPU(stream, ref offsetRef, admissibleCount);
+				countView.CopyFromCPU(stream, ref countRef, admissibleCount);
+				cycleView.CopyFromCPU(stream, ref cycleRef, admissibleCount);
+				exponentViewDevice.CopyFromCPU(stream, ref exponentRef, admissibleCount);
+
+				int sentinel = int.MaxValue;
+				hitIndexView.CopyFromCPU(stream, ref sentinel, 1);
+
+				kernel.Launch(stream, 1, new Index1D(admissibleCount), divisorDataView, offsetView, countView, exponentViewDevice, cycleView, hitsView, hitIndexView);
+
+				int firstHit = sentinel;
+				hitIndexView.CopyToCPU(stream, ref firstHit, 1);
+				stream.Synchronize();
+				AcceleratorStreamPool.Return(acceleratorIndex, stream);
+				int hitIndex = firstHit >= admissibleCount ? -1 : firstHit;
+				bool hitFound = hitIndex >= 0;
+				composite = hitFound;
+				int lastIndex = admissibleCount - 1;
+				lastProcessedLocal = hitFound ? divisorSpan[hitIndex] : divisorSpan[lastIndex];
 			}
 
-			remainder10 = localRemainder10;
-			remainder8 = localRemainder8;
-			remainder3 = localRemainder3;
-			remainder7 = localRemainder7;
-			remainder11 = localRemainder11;
-
-			processedCount += (ulong)chunkCount;
-
-			UInt128 lastDivisor128 = nextDivisor128 - twoP128;
-			lastProcessed = (ulong)lastDivisor128;
-			currentDivisor128 = nextDivisor128;
-			remainingCount -= (ulong)chunkCount;
-
-			if (admissibleCount == 0)
-			{
-				continue;
-			}
-
-			var stream = AcceleratorStreamPool.Rent(acceleratorIndex);
-			divisorDataView.CopyFromCPU(stream, ref divisorDataRef, admissibleCount);
-			offsetView.CopyFromCPU(stream, ref offsetRef, admissibleCount);
-			countView.CopyFromCPU(stream, ref countRef, admissibleCount);
-			cycleView.CopyFromCPU(stream, ref cycleRef, admissibleCount);
-			exponentViewDevice.CopyFromCPU(stream, ref exponentRef, admissibleCount);
-
-			int sentinel = int.MaxValue;
-			hitIndexView.CopyFromCPU(stream, ref sentinel, 1);
-
-			kernel.Launch(stream, 1, new Index1D(admissibleCount), divisorDataView, offsetView, countView, exponentViewDevice, cycleView, hitsView, hitIndexView);
-
-			int firstHit = sentinel;
-			hitIndexView.CopyToCPU(stream, ref firstHit, 1);
-			stream.Synchronize();
-			AcceleratorStreamPool.Return(acceleratorIndex, stream);
-			int hitIndex = firstHit >= admissibleCount ? -1 : firstHit;
-			bool hitFound = hitIndex >= 0;
-			composite = hitFound;
-			int lastIndex = admissibleCount - 1;
-			lastProcessed = hitFound ? divisorSpan[hitIndex] : divisorSpan[lastIndex];
+			return rangeRemaining == 0UL;
 		}
 
-		processedAll = remainingCount == 0UL;
-		coveredRange = composite || processedAll || (currentDivisor128 > allowedMax128);
+		bool processedTop = true;
+		bool processedBottom = true;
+
+		if (startK <= maxK)
+		{
+			processedTop = ProcessRange(
+				gpu,
+				prime,
+				twoP128,
+				allowedMax128,
+				step10,
+				step8,
+				step3,
+				step7,
+				step11,
+				decimalMask,
+				divisorDataView,
+				offsetView,
+				countView,
+				cycleView,
+				exponentViewDevice,
+				hitsView,
+				hitIndexView,
+				divisorSpan,
+				exponentSpan,
+				divisorDataSpan,
+				offsetSpan,
+				countSpan,
+				cycleSpan,
+				divisorPool,
+				chunkCountBaseline,
+				acceleratorIndex,
+				ref composite,
+				ref processedCountLocal,
+				ref lastProcessedLocal,
+				startK,
+				maxK,
+				kernel);
+			if (composite)
+			{
+				coveredRange = true;
+				processedCount = processedCountLocal;
+				lastProcessed = lastProcessedLocal;
+				return true;
+			}
+		}
+
+		ulong lowerEnd = startK > 1UL ? startK - 1UL : 0UL;
+		if (!composite && lowerEnd >= 1UL)
+		{
+			lowerEnd = Math.Min(lowerEnd, maxK);
+			processedBottom = ProcessRange(
+				gpu,
+				prime,
+				twoP128,
+				allowedMax128,
+				step10,
+				step8,
+				step3,
+				step7,
+				step11,
+				decimalMask,
+				divisorDataView,
+				offsetView,
+				countView,
+				cycleView,
+				exponentViewDevice,
+				hitsView,
+				hitIndexView,
+				divisorSpan,
+				exponentSpan,
+				divisorDataSpan,
+				offsetSpan,
+				countSpan,
+				cycleSpan,
+				divisorPool,
+				chunkCountBaseline,
+				acceleratorIndex,
+				ref composite,
+				ref processedCountLocal,
+				ref lastProcessedLocal,
+				1UL,
+				lowerEnd,
+				kernel);
+		}
+
+		processedAll = processedTop && processedBottom;
+		coveredRange = composite || processedAll;
+		processedCount = processedCountLocal;
+		lastProcessed = lastProcessedLocal;
 		return composite;
 	}
 

PerfectNumbers.Core/IMersenneNumberDivisorByDivisorTester.cs

@@ -6,6 +6,8 @@ public interface IMersenneNumberDivisorByDivisorTester
 {
     int BatchSize { get; set; }
 
+    ulong MinK { get; set; }
+
     void ConfigureFromMaxPrime(ulong maxPrime);
 
     ulong DivisorLimit { get; }

PerfectNumbers.Core/PerfectNumberConstants.cs

@@ -8,7 +8,7 @@ public static class PerfectNumberConstants
 	public const int DefaultSmallPrimeFactorSlotCount = 64;
 	public const int DefaultSpecialMaxFactorCapacity = 1024;
     public const ulong ExtraDivisorCycleSearchLimit = 64UL;
-	public const int GpuFrequency = 4 - 1;
+	public const int GpuFrequency = 256 - 1;
     public const int MaxQForDivisorCycles = 4_000_000;
     public static readonly uint PrimesLimit = 1_000_000; //(ulong)Array.MaxLength;// 1_000_000;
     public const int MaxOddPowersCount = 128;

PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs

@@ -54,11 +54,11 @@ internal static partial class PrimeOrderCalculator
 
 		ulong phi = prime - 1UL;
 
-		if (PrimeOrderGpuHeuristics.TryCalculateOrder(gpu, prime, previousOrder, config, divisorData, out ulong gpuOrder))
+		// if (PrimeOrderGpuHeuristics.TryCalculateOrder(gpu, prime, previousOrder, config, divisorData, out ulong gpuOrder))
 		// if (IsGpuHeuristicDevice && PrimeOrderGpuHeuristics.TryCalculateOrder(gpu, prime, previousOrder, config, divisorData, out ulong gpuOrder))
-		{
-			return gpuOrder;
-		}
+		// {
+		// 	return gpuOrder;
+		// }
 
 		PartialFactorResult phiFactors = PartialFactor(gpu, phi, config);
 
@@ -137,7 +137,7 @@ internal static partial class PrimeOrderCalculator
 
 		Span<ulong> stackBuffer = stackalloc ulong[length];
 
-		if (length <= 8)
+		if (length <= 7)
 		{
 			return EvaluateSpecialMaxCandidates(stackBuffer, factorSpan, phi, prime, divisorData);
 		}
@@ -1106,19 +1106,19 @@ internal static partial class PrimeOrderCalculator
 		uint limit = config.SmallFactorLimit == 0 ? uint.MaxValue : config.SmallFactorLimit;
 		ulong remaining = value;
 
-		bool gpuFactored = false;
-		if (IsGpuHeuristicDevice)
-		{
-			gpuFactored = PrimeOrderGpuHeuristics.TryPartialFactor(gpu, value, limit, primeSlots, exponentSlots, out factorCount, out remaining);
-		}
+		// bool gpuFactored = false;
+		// if (IsGpuHeuristicDevice)
+		// {
+		// 	gpuFactored = PrimeOrderGpuHeuristics.TryPartialFactor(gpu, value, limit, primeSlots, exponentSlots, out factorCount, out remaining);
+		// }
 
 		List<PendingEntry> pending = ThreadStaticPools.RentPrimeOrderPendingEntryList(2);
 		Stack<ulong>? compositeStack = null;
 		PrimeTester primeTester = PrimeTester.Exclusive;
 		// HeuristicPrimeTester? tester = _tester ??= new();
 
-		if (!gpuFactored)
-		{
+		// if (!gpuFactored)
+		// {
 			PopulateSmallPrimeFactorsCpu(
 				value,
 				limit,
@@ -1128,7 +1128,7 @@ internal static partial class PrimeOrderCalculator
 				ref exponentSlotArray,
 				out factorCount,
 				out remaining);
-		}
+		// }
 
 
 		if (remaining > 1UL)
@@ -1176,7 +1176,7 @@ internal static partial class PrimeOrderCalculator
 					// bool isPrime = HeuristicCombinedPrimeTester.IsPrimeCpu(composite);
 					// bool isPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite);
 					bool runOnGpu = RunOnGpu();
-					bool isPrime = !runOnGpu ? HeuristicCombinedPrimeTester.IsPrimeCpu(composite) : HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite);
+					bool isPrime = !runOnGpu ? PrimeTester.IsPrime(composite) : HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite);
 					// bool isPrime = PrimeTester.IsPrime(composite);
 					// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
 
@@ -1244,15 +1244,15 @@ internal static partial class PrimeOrderCalculator
 			{
 				// bool isPrime = HeuristicCombinedPrimeTester.IsPrimeCpu(composite);
 				// bool isPrime = PrimeTester.IsPrime(composite);
-				// bool isPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(composite);
+				bool isPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite);
 				// bool isPrime = PrimeTester.IsPrimeInternal(composite, CancellationToken.None);
 
 				// Atomic.Add(ref _partialFactorPendingHits, 1UL);
 				// Console.WriteLine($"Partial factor pending hits {Volatile.Read(ref _partialFactorPendingHits)}");
 
-				bool isPrime = RunOnGpu()
-					? HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite)
-					: HeuristicCombinedPrimeTester.IsPrimeCpu(composite);
+				// bool isPrime = RunOnGpu()
+				// 	? HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite)
+				// 	: PrimeTester.IsPrime(composite);
 				// bool isPrime = PrimeTester.IsPrime(composite);
 				// bool isPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, composite);
 				// bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
@@ -1287,7 +1287,7 @@ internal static partial class PrimeOrderCalculator
 		{
 			// cofactorIsPrime = PrimeTester.IsPrime(cofactor);
 			// cofactorIsPrime = HeuristicCombinedPrimeTester.IsPrimeCpu(cofactor);
-			// cofactorIsPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(cofactor);
+			cofactorIsPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, cofactor);
 			// cofactorIsPrime = PrimeTester.IsPrimeInternal(cofactor, CancellationToken.None);
 
 			// Atomic.Add(ref _partialFactorCofactorHits, 1UL);
@@ -1295,9 +1295,9 @@ internal static partial class PrimeOrderCalculator
 
 			// cofactorIsPrime = HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, cofactor);
 			// cofactorIsPrime = PrimeTester.IsPrimeGpu(gpu, cofactor);
-			cofactorIsPrime = RunOnGpu()
-				? HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, cofactor)
-				: HeuristicCombinedPrimeTester.IsPrimeCpu(cofactor);
+			// cofactorIsPrime = RunOnGpu()
+			// 	? HeuristicCombinedPrimeTester.IsPrimeGpu(gpu, cofactor)
+			// 	: PrimeTester.IsPrime(cofactor);
 			// cofactorIsPrime = PrimeTester.IsPrime(cofactor);
 			// cofactorIsPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(cofactor);
 		}
@@ -1385,7 +1385,7 @@ internal static partial class PrimeOrderCalculator
 	private static bool RunOnGpu()
 	{
 		// return false;
-		return true;
+		// return true;
 		// int cpuCount;
 		
 		// lock(_sync)