BigInteger-friendly steppers added. MersenneResidueStepper converted to struct. Manual residue tracking replaced with steppers. Modulo operations replaced with steppers.

PerfectNumbers.Core/CycleRemainderStepper.cs

@@ -2,37 +2,20 @@ using System.Runtime.CompilerServices;
 
 namespace PerfectNumbers.Core;
 
-public struct CycleRemainderStepper
+public struct CycleRemainderStepper(ulong cycleLength)
 {
-    private readonly ulong _cycleLength;
-    private ulong _previousPrime;
-    private ulong _currentRemainder;
-    private bool _hasState;
-
-    public CycleRemainderStepper(ulong cycleLength)
-    {
-        if (cycleLength == 0UL)
-        {
-            throw new ArgumentOutOfRangeException(nameof(cycleLength), "Cycle length must be non-zero.");
-        }
-
-        _cycleLength = cycleLength;
-        _previousPrime = 0UL;
-        _currentRemainder = 0UL;
-        _hasState = false;
-    }
+    private readonly ulong _cycleLength = cycleLength;
+    private ulong _previousPrime = 0UL;
+    private ulong _currentRemainder = 0UL;
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
 	public void Reset()
 	{
-		// TODO: Inline this reset at the call sites so the hot loops reuse struct reinitialization
-		// measured fastest in MersenneDivisorCycleLengthGpuBenchmarks, avoiding the extra
-		// method call when scanners need to restart stepping.
 		_previousPrime = 0UL;
 		_currentRemainder = 0UL;
-		_hasState = false;
 	}
 
+	[MethodImpl(MethodImplOptions.AggressiveInlining)]
     public ulong Initialize(ulong prime)
     {
         ulong cycleLength = _cycleLength;
@@ -44,24 +27,15 @@ public struct CycleRemainderStepper
             // MersenneDivisorCycleLengthGpuBenchmarks winner for both CPU and GPU call sites.
             remainder %= cycleLength;
         }
+
         _previousPrime = prime;
         _currentRemainder = remainder;
-        _hasState = true;
         return remainder;
     }
 
+	[MethodImpl(MethodImplOptions.AggressiveInlining)]
     public ulong ComputeNext(ulong prime)
     {
-        if (!_hasState)
-        {
-            throw new InvalidOperationException("CycleRemainderStepper must be initialized before computing.");
-        }
-
-        if (prime <= _previousPrime)
-        {
-            throw new ArgumentOutOfRangeException(nameof(prime), "Primes must be processed in strictly increasing order.");
-        }
-
         ulong cycleLength = _cycleLength;
         ulong delta = prime - _previousPrime;
         _previousPrime = prime;
@@ -90,13 +64,4 @@ public struct CycleRemainderStepper
         }
         return _currentRemainder;
     }
-
-    public void CaptureState(out ulong previousPrime, out ulong previousRemainder, out bool hasState)
-    {
-        // TODO: Expose these fields directly once the residue scanners adopt the single-cycle helper
-        // so the hot path can read them without paying for an additional wrapper call per iteration.
-        previousPrime = _previousPrime;
-        previousRemainder = _currentRemainder;
-        hasState = _hasState;
-    }
 }