GPU warmup disabled when no GPU is in use.

EvenPerfectBitScanner/Program.cs

@@ -118,10 +118,18 @@ private static ThreadLocal<object>? MersenneTesters;
 		EnvironmentConfiguration.MinK = _cliArguments.MinK;
 		EnvironmentConfiguration.GpuBatchSize = Math.Max(1, _cliArguments.ScanBatchSize);
 		EnvironmentConfiguration.GpuRatio = _cliArguments.GpuRatio;
+		EnvironmentConfiguration.MersenneDevice = _cliArguments.MersenneDevice;
 		EnvironmentConfiguration.OrderDevice = _cliArguments.OrderDevice;
 		EnvironmentConfiguration.UsePow2GroupDivisors = _cliArguments.ByDivisorKIncrementMode == ByDivisorKIncrementMode.Pow2Groups;
 		EnvironmentConfiguration.ByDivisorSpecialRange = _cliArguments.ByDivisorSpecialRange;
-		EnvironmentConfiguration.RollingAccelerators = Math.Min(Math.Min(PerfectNumberConstants.RollingAccelerators, gpuPrimeThreads), threadCount);
+
+		bool useGpu = _cliArguments.OrderDevice == ComputationDevice.Hybrid || _cliArguments.OrderDevice == ComputationDevice.Gpu ||
+				_cliArguments.MersenneDevice == ComputationDevice.Hybrid || _cliArguments.MersenneDevice == ComputationDevice.Gpu;
+
+		EnvironmentConfiguration.RollingAccelerators = useGpu 
+			? Math.Min(Math.Min(PerfectNumberConstants.RollingAccelerators, gpuPrimeThreads), threadCount)
+			: 0;
+
 		EnvironmentConfiguration.Initialize();
 
 			// NttGpuMath.GpuTransformBackend = _cliArguments.NttBackend;
@@ -137,8 +145,12 @@ private static ThreadLocal<object>? MersenneTesters;
 			UnboundedTaskScheduler.ConfigureThreadCount(threadCount);
 			PrimeTester.GpuBatchSize = gpuPrimeBatch;
 			GpuPrimeWorkLimiter.SetLimit(gpuPrimeThreads);
-			Console.WriteLine("Warming up GPU kernels");
-			PrimeTester.WarmUpGpuKernels(EnvironmentConfiguration.RollingAccelerators);
+			if (useGpu)
+			{
+				Console.WriteLine("Warming up GPU kernels");
+				PrimeTester.WarmUpGpuKernels(EnvironmentConfiguration.RollingAccelerators);
+			}
+
 			// PrimeTester.WarmUpGpuKernels(gpuPrimeThreads >> 4);
 			Console.WriteLine("Starting up threads...");
 			_ = UnboundedTaskScheduler.Instance;

PerfectNumbers.Core/DivisorCycleCache.cs

@@ -33,12 +33,20 @@ public sealed class DivisorCycleCache
 
 	private DivisorCycleCache(int divisorCyclesBatchSize)
 	{
+		bool useGpu = EnvironmentConfiguration.MersenneDevice == ComputationDevice.Hybrid ||
+					  EnvironmentConfiguration.MersenneDevice == ComputationDevice.Gpu ||
+					  !EnvironmentConfiguration.UseCpuOrder;
+
 		_divisorCyclesBatchSize = Math.Max(1, divisorCyclesBatchSize);
-		var acceleratorIndex = AcceleratorPool.Shared.Rent();
-		_acceleratorIndex = acceleratorIndex;
-		Accelerator accelerator = AcceleratorPool.Shared.Accelerators[acceleratorIndex];
-		_accelerator = accelerator;
-		_gpuKernel = LoadKernel(accelerator);
+		if (useGpu)
+		{
+			var acceleratorIndex = AcceleratorPool.Shared.Rent();
+			_acceleratorIndex = acceleratorIndex;
+			Accelerator accelerator = AcceleratorPool.Shared.Accelerators[acceleratorIndex];
+			_accelerator = accelerator;
+			_gpuKernel = LoadKernel(accelerator);			
+		}
+
 		_snapshot = MersenneDivisorCyclesCpu.Shared.ExportSmallCyclesSnapshot();
 	}
 

PerfectNumbers.Core/EnvironmentConfiguration.cs

@@ -11,6 +11,7 @@ public static class EnvironmentConfiguration
 	public static ulong DivisorLimit = ulong.MaxValue;
 	public static int GpuBatchSize = GpuConstants.ScanBatchSize;
 	public static int GpuRatio = PerfectNumberConstants.GpuRatio;
+	public static ComputationDevice MersenneDevice = ComputationDevice.Cpu;
 	public static BigInteger MinK = BigInteger.One;
 	public static ComputationDevice OrderDevice = ComputationDevice.Cpu;
 	public static int RollingAccelerators = PerfectNumberConstants.RollingAccelerators;