% 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();
+    }
+}
+

EvenPerfectBitScanner.Benchmarks/Mod10ULongBenchmarks.cs

@@ -5,7 +5,7 @@ using PerfectNumbers.Core;
 namespace EvenPerfectBitScanner.Benchmarks;
 
 [MemoryDiagnoser]
-public class Mod10Benchmarks
+public class Mod10ULongBenchmarks
 {
     [Params(3UL, 8191UL, 131071UL, 2147483647UL)]
     public ulong Value { get; set; }
@@ -13,14 +13,7 @@ public class Mod10Benchmarks
     [Benchmark(Baseline = true)]
     public ulong LegacyModulo()
     {
-		ulong value = Value;
-		UInt128 zero = UInt128.Zero;
-		if (value == zero)
-		{
-			return 0UL;
-		}
-
-		return value % 10UL;
+		return Value % 10UL;
     }
 
     [Benchmark]

EvenPerfectBitScanner.Benchmarks/Mod10_8_5_3StepsBenchmarks.cs

@@ -0,0 +1,33 @@
+using System.Numerics;
+using BenchmarkDotNet.Attributes;
+using PerfectNumbers.Core;
+
+namespace EvenPerfectBitScanner.Benchmarks;
+
+[MemoryDiagnoser]
+public class Mod10_8_5_3StepsBenchmarks
+{
+    [Params(3UL, 8191UL, 131071UL, 2147483647UL)]
+    public ulong Value { get; set; }
+
+    [Benchmark(Baseline = true)]
+    public (ulong Mod10, ulong Mod8, ulong Mod3, ulong Mod5) LegacyModulo()
+    {
+		UInt128 value = Value;
+		ulong mod10 = (ulong)(value % 10UL) % 10UL;
+		ulong mod8 = (ulong)(value % 8UL);
+		ulong mod3 = (ulong)(value % 3UL);
+		ulong mod5 = (ulong)(value % 5UL);
+        return (mod10, mod8, mod3, mod5);
+    }
+
+    [Benchmark]
+    public (ulong Mod10, ulong Mod8, ulong Mod3, ulong Mod5) ModMethodModulo()
+    {
+		Value.Mod10_8_5_3(out ulong mod10, out ulong mod8, out ulong mod5, out ulong mod3);
+		// Step residues for q += 2*p
+		mod10 = mod10.Mod10();
+        return (mod10, mod8, mod3, mod5);
+    }
+}
+