DivisorSet scans added as EnumDependentTemplate to MersenneNumberDivisorByDivisorCpuTesterWithTemplate. New Pow2Groups scan implemented based on statistics for high divisors. MersenneNumberDivisorByDivisorPrimeScan sessions integrated into MersenneNumberDivisorByDivisorPrimeScanSessionWithTemplate. Various micro optimizations to eliminate variable, unnecessary struct creations and continue scans in higher divisor ranges, when lower ranges are exhausted. --bydivisor-k-increment command-line argument added.

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorPrimeScanSessionWithTemplate.cs

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+using System.Globalization;
+using System.Globalization;
+using System.IO;
+using System.Numerics;
+using PerfectNumbers.Core.Gpu;
+using PerfectNumbers.Core.Gpu.Accelerators;
+
+#if DivisorSet_Pow2Groups
+using TesterCpu = PerfectNumbers.Core.Cpu.MersenneNumberDivisorByDivisorCpuTesterWithForPow2GroupsDivisorSetForCpuOrder;
+using TesterHybrid = PerfectNumbers.Core.Cpu.MersenneNumberDivisorByDivisorCpuTesterWithForPow2GroupsDivisorSetForHybridOrder;
+using TesterGpu = PerfectNumbers.Core.Cpu.MersenneNumberDivisorByDivisorCpuTesterWithForPow2GroupsDivisorSetForGpuOrder;
+#else
+using TesterCpu = PerfectNumbers.Core.Cpu.MersenneNumberDivisorByDivisorCpuTesterWithForOneByOneDivisorSetForCpuOrder;
+using TesterHybrid = PerfectNumbers.Core.Cpu.MersenneNumberDivisorByDivisorCpuTesterWithForOneByOneDivisorSetForHybridOrder;
+using TesterGpu = PerfectNumbers.Core.Cpu.MersenneNumberDivisorByDivisorCpuTesterWithForOneByOneDivisorSetForGpuOrder;
+#endif
+
+namespace PerfectNumbers.Core.Cpu;
+
+[EnumDependentTemplate(typeof(DivisorSet))]
+[DeviceDependentTemplate(typeof(ComputationDevice))]
+[NameSuffix("Order")]
+internal struct MersenneNumberDivisorByDivisorPrimeScanSessionWithTemplate
+{
+#if DEVICE_GPU
+	private TesterGpu _tester;
+#elif DEVICE_HYBRID
+	private TesterHybrid _tester;
+#else
+	private TesterCpu _tester;
+#endif
+
+	private readonly Action _markComposite;
+	private readonly Action _clearComposite;
+	private readonly Action<ulong, bool, bool, bool, BigInteger> _printResult;
+
+	public MersenneNumberDivisorByDivisorPrimeScanSessionWithTemplate(
+#if DEVICE_GPU
+		in TesterGpu prototype,
+#elif DEVICE_HYBRID
+		in TesterHybrid prototype,
+#else
+		in TesterCpu prototype,
+#endif
+		Action markComposite,
+		Action clearComposite,
+		Action<ulong, bool, bool, bool, BigInteger> printResult)
+	{
+		_tester = new()
+		{
+			DivisorLimit = prototype.DivisorLimit,
+			MinK = EnvironmentConfiguration.MinK,
+		};
+
+		_markComposite = markComposite;
+		_clearComposite = clearComposite;
+		_printResult = printResult;
+	}
+
+	public void ProcessPrime(ulong prime)
+	{
+		try
+		{
+			Console.WriteLine($"Processing {prime}");
+			string stateFile = Path.Combine(
+				PerfectNumberConstants.ByDivisorStateDirectory,
+				prime.ToString(CultureInfo.InvariantCulture) + ".bin");
+
+			ConfigureForPrime(stateFile);
+
+			bool isPrime = _tester.IsPrime(prime, out bool divisorsExhausted, out BigInteger divisor);
+
+			if (!isPrime)
+			{
+				if (!string.IsNullOrEmpty(stateFile) && File.Exists(stateFile))
+				{
+					File.Delete(stateFile);
+				}
+
+				_markComposite();
+				_printResult(prime, true, true, false, divisor);
+				Console.WriteLine($"Finished processing {prime}");
+				return;
+			}
+
+			_clearComposite();
+			_printResult(prime, true, divisorsExhausted, true, divisor);
+			Console.WriteLine($"Finished processing {prime}");
+		}
+		catch (Exception ex)
+		{
+			Console.WriteLine($"Error processing {ex.Message} {ex.StackTrace}");
+			Environment.Exit(1);
+		}
+	}
+
+	private void ConfigureForPrime(string stateFile)
+	{
+		BigInteger resumeK = EnvironmentConfiguration.MinK;
+		if (File.Exists(stateFile))
+		{
+			if (MersenneNumberDivisorByDivisorTester.TryReadLastSavedK(stateFile, out BigInteger lastK))
+			{
+				resumeK = lastK + BigInteger.One;
+				_tester.ResumeFromState(stateFile, lastK, resumeK);
+			}
+			else
+			{
+				_tester.ResumeFromState(stateFile, BigInteger.Zero, resumeK);
+			}
+		}
+		else
+		{
+			_tester.ResumeFromState(stateFile, BigInteger.Zero, resumeK);
+		}
+
+		_tester.ResetStateTracking();
+	}
+
+	public void Dispose()
+	{
+#if DEVICE_GPU || DEVICE_HYBRID
+		PrimeOrderCalculatorAccelerator.Return(_tester.Accelerator);
+#endif
+	}
+}