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BitContradiction performance improvements. Exact powers of 2 cases will reuse previous calculation results and transform them for the next q divisor.

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mlemanczyk committed 2026-01-24 01:28:09 +01:00
1 parent b014fdb7f1
commit b2a6a1c332
2 files changed
+141 -30
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PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTesterWithTemplate.cs
+55 -9
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@@ -1409,7 +1409,7 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneN
computedCycle = prime;
// }
decided = TryExactBitTreeCheck(computedCycle, divisor, out divides);
decided = TryExactBitTreeCheck(computedCycle, divisor, currentK, out divides);
if (!decided)
{
throw new InvalidOperationException($"BitTree check did not decide for p={prime}, divisor={divisor} (k={currentK}).");
@@ -1437,7 +1437,7 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneN
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private bool TryExactBitTreeCheck(ulong exponent, BigInteger divisor, out bool divides)
private bool TryExactBitTreeCheck(ulong exponent, BigInteger divisor, BigInteger currentK, out bool divides)
{
#if DETAILED_LOG
Stopwatch sw = Stopwatch.StartNew();
@@ -4617,7 +4617,7 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneN
sw.Reset();
sw.Start();
bool decided = TryExactBitContradictionCheck(prime, divisor, out divides);
bool decided = TryExactBitContradictionCheck(prime, divisor, currentK, out divides);
sw.Stop();
if (!decided)
{
@@ -4711,9 +4711,17 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneN
[ThreadStatic]
private static int[]? _qBits;
[ThreadStatic]
private static int[]? _pow2Offsets;
[ThreadStatic]
private static int _pow2OffsetCount;
[ThreadStatic]
private static BigInteger _pow2K;
[ThreadStatic]
private static bool _hasPow2K;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static bool TryExactBitContradictionCheck(ulong prime, BigInteger divisor, out bool divides)
private static bool TryExactBitContradictionCheck(ulong prime, BigInteger divisor, BigInteger currentK, out bool divides)
{
divides = false;
// const ulong DebugTopDownDivisor = 1209708008767UL;
@@ -4774,14 +4782,52 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneN
int[] oneOffsets = _qBits!;
// Span<int> oneOffsets = stackalloc int[qBitLength];
int oneCount = 0;
for (int i = 0; i < qBitLength; i++)
bool isPowerOfTwo = currentK.IsPowerOfTwo;
bool usedPow2Offsets = false;
int[]? pow2Offsets = _pow2Offsets;
int pow2OffsetCount = _pow2OffsetCount;
BigInteger pow2K = _pow2K;
bool hasPow2K = _hasPow2K;
if (isPowerOfTwo && hasPow2K && pow2Offsets != null && pow2OffsetCount > 0 && currentK == (pow2K << 1))
{
if (((divisor >> i) & BigInteger.One) == BigInteger.One)
int needed = pow2OffsetCount + 1;
if (needed <= oneOffsets.Length)
{
oneOffsets[oneCount++] = i;
oneOffsets[0] = 0;
for (int i = 0; i < pow2OffsetCount; i++)
{
oneOffsets[i + 1] = pow2Offsets[i] + 1;
}
oneCount = needed;
usedPow2Offsets = true;
}
}
if (!usedPow2Offsets)
{
for (int i = 0; i < qBitLength; i++)
{
if (((divisor >> i) & BigInteger.One) == BigInteger.One)
{
oneOffsets[oneCount++] = i;
}
}
}
if (isPowerOfTwo)
{
int[]? pow2OffsetsTarget = _pow2Offsets;
if (pow2OffsetsTarget == null || pow2OffsetsTarget.Length < oneCount)
{
pow2OffsetsTarget = new int[oneCount];
_pow2Offsets = pow2OffsetsTarget;
}
Array.Copy(oneOffsets, pow2OffsetsTarget, oneCount);
_pow2OffsetCount = oneCount;
_pow2K = currentK;
_hasPow2K = true;
}
if (oneCount == 0)
{
divides = false;
@@ -4791,9 +4837,9 @@ public struct MersenneNumberDivisorByDivisorCpuTesterWithTemplate() : IMersenneN
ReadOnlySpan<int> oneOffsetsSlice = oneOffsets[..oneCount];
// BitContradictionSolverWithQMultiplier.SetDebugEnabled(true);
#if DETAILED_LOG
bool decided = BitContradictionSolverWithAMultiplier.TryCheckDivisibilityFromOneOffsets(oneOffsetsSlice, prime, out divides, out var reason);
bool decided = BitContradictionSolverWithAMultiplier.TryCheckDivisibilityFromOneOffsets(oneOffsetsSlice, prime, currentK, isPowerOfTwo, out divides, out var reason);
#else
bool decided = BitContradictionSolverWithAMultiplier.TryCheckDivisibilityFromOneOffsets(oneOffsetsSlice, prime, out divides);
bool decided = BitContradictionSolverWithAMultiplier.TryCheckDivisibilityFromOneOffsets(oneOffsetsSlice, prime, currentK, isPowerOfTwo, out divides);
#endif
// BitContradictionSolverWithQMultiplier.SetDebugEnabled(false);
if (decided && divides)