% 10 operations replaces with UInt128/ulong.Mod10 methods

EvenPerfectBitScanner.Benchmarks/Mod10UInt128Benchmarks.cs

@@ -0,0 +1,52 @@
+using BenchmarkDotNet.Attributes;
+using PerfectNumbers.Core;
+
+namespace EvenPerfectBitScanner.Benchmarks;
+
+[MemoryDiagnoser]
+public class Mod10UInt128Benchmarks
+{
+	[Params(3UL, 8191UL, 131071UL, 2147483647UL)]
+	public UInt128 Value { get; set; }
+
+	[Benchmark(Baseline = true)]
+	public UInt128 StandardModulo()
+	{
+		return Value % 10UL;
+	}
+
+	[Benchmark]
+	public ulong ModWithHighLowModulo()
+	{
+		// Split and fold under mod 10: 2^64 ≡ 6 (mod 10)
+		ulong value = (ulong)Value;
+		ulong high = value >> 64;
+		ulong low = value;
+		ulong highRem = high.Mod10();
+		ulong lowRem = low.Mod10();
+		ulong combined = lowRem + highRem * 6UL;
+		return combined.Mod10();
+	}
+
+    [Benchmark]
+    public ulong ModWithLoopModulo()
+    {
+		UInt128 value = Value;
+		UInt128 zero = UInt128.Zero;
+		if (value == zero)
+			return 0UL;
+
+		ulong result = (ulong)value;
+		UInt128 high = value >> 64;
+
+		while (high != zero)
+		{
+			// 2^64 ≡ 6 (mod 10)
+			result = (result + (ulong)high * 6UL).Mod10();
+			high >>= 64;
+		}
+
+		return result.Mod10();
+    }
+}
+