Restore GPU-backed UInt128 pow2 Montgomery helper

EvenPerfectBitScanner.Benchmarks/GpuRationalBenchmarks.cs

@@ -0,0 +1,29 @@
+using BenchmarkDotNet.Attributes;
+using PerfectNumbers.Core.Gpu;
+
+namespace EvenPerfectBitScanner.Benchmarks;
+
+[MemoryDiagnoser]
+public class GpuRationalBenchmarks
+{
+    private static readonly GpuRational Left = new(new GpuUInt128(3UL), new GpuUInt128(4UL));
+    private static readonly GpuRational Right = new(new GpuUInt128(5UL), new GpuUInt128(6UL));
+    private static readonly GpuUInt128 IntegerLeft = new(3UL);
+    private static readonly GpuUInt128 IntegerRight = new(5UL);
+
+    [Benchmark]
+    public GpuRational AddRational()
+    {
+        GpuRational value = Left;
+        value = value + Right;
+        return value;
+    }
+
+    [Benchmark]
+    public GpuUInt128 AddInteger()
+    {
+        GpuUInt128 value = IntegerLeft;
+        value.Add(IntegerRight);
+        return value;
+    }
+}