Add GPU options for by-divisor Montgomery data

EvenPerfectBitScanner/Program.cs

@@ -76,6 +76,7 @@ internal static class Program
         bool useDivisor = false;     // M_p divisibility by specific divisor
         bool useByDivisor = false;   // Iterative divisor scan across primes		UInt128 divisor = UInt128.Zero;
         ByDivisorDeltasDevice byDivisorDeltasDevice = ByDivisorDeltasDevice.Cpu;
+        ByDivisorMontgomeryDevice byDivisorMontgomeryDevice = ByDivisorMontgomeryDevice.Cpu;
                                      // Device routing
         bool useGpuCycles = true;
         bool mersenneOnGpu = true;   // controls Lucas/incremental/pow2mod device
@@ -200,6 +201,23 @@ internal static class Program
                     return;
                 }
             }
+            else if (arg.StartsWith("--bydivisor-montgomery-device=", StringComparison.OrdinalIgnoreCase))
+            {
+                ReadOnlySpan<char> deviceValue = arg.AsSpan(arg.IndexOf('=') + 1);
+                if (deviceValue.Equals("gpu", StringComparison.OrdinalIgnoreCase))
+                {
+                    byDivisorMontgomeryDevice = ByDivisorMontgomeryDevice.Gpu;
+                }
+                else if (deviceValue.Equals("cpu", StringComparison.OrdinalIgnoreCase))
+                {
+                    byDivisorMontgomeryDevice = ByDivisorMontgomeryDevice.Cpu;
+                }
+                else
+                {
+                    Console.WriteLine("Invalid --bydivisor-montgomery-device value. Expected cpu or gpu.");
+                    return;
+                }
+            }
             else if (arg.StartsWith("--prime-test-limit=", StringComparison.OrdinalIgnoreCase))
             {
                 ReadOnlySpan<char> value = arg.AsSpan(arg.IndexOf('=') + 1);
@@ -552,6 +570,7 @@ internal static class Program
             if (_byDivisorTester is MersenneNumberDivisorByDivisorCpuTester cpuByDivisorTester)
             {
                 cpuByDivisorTester.DeltasDevice = byDivisorDeltasDevice;
+                cpuByDivisorTester.MontgomeryDevice = byDivisorMontgomeryDevice;
             }
         }
 
@@ -1007,6 +1026,7 @@ internal static class Program
         Console.WriteLine("  --divisor-cycles-limit=<value> cycle search iterations when --mersenne=divisor");
         Console.WriteLine("  --prime-test-limit=<value>   Time limit for --mersenne=bydivisor prime checks (e.g. 5s, 500ms)");
         Console.WriteLine("  --bydivisor-deltas-device=cpu|gpu  Device for --mersenne=bydivisor residue batches (default: cpu)");
+        Console.WriteLine("  --bydivisor-montgomery-device=cpu|gpu  Device for Montgomery data when using --mersenne=bydivisor (default: cpu)");
         Console.WriteLine("  --use-order            test primality via q order");
         Console.WriteLine("  --workaround-mod       avoid '%' operator on the GPU");
         // mod-automaton removed