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BitContradiction performance improvements. Next variables removed.

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mlemanczyk committed 2026-01-25 03:05:22 +01:00
1 parent 3ca99460bb
commit a4aead2802
1 file changed
+19 -37
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PerfectNumbers.Core/ByDivisor/BitContradictionSolverWithAMultiplier.cs
+19 -37
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@@ -1603,9 +1603,7 @@ internal static class BitContradictionSolverWithAMultiplier
// Force low bits of 'a' from a ≡ -q^{-1} (mod 2^1024). // Force low bits of 'a' from a ≡ -q^{-1} (mod 2^1024).
// This is a necessary condition for q | (2^p - 1) when p >= 1024 (true here). // This is a necessary condition for q | (2^p - 1) when p >= 1024 (true here).
const int ForcedBits = ForcedALowBits; BigInteger mask = Pow2Provider.BigIntegerMinusOne(ForcedALowBits);
const int ForcedBitsMinusOne = ForcedALowBits - 1;
BigInteger mask = Pow2Provider.BigIntegerMinusOne(ForcedBits);
BigInteger qMod2k; BigInteger qMod2k;
bool usedPow2Transform = false; bool usedPow2Transform = false;
if (isPowerOfTwo && workSet.HasLastPow2QMod2k && workSet.LastPow2K != BigInteger.Zero && k == (workSet.LastPow2K << 1)) if (isPowerOfTwo && workSet.HasLastPow2QMod2k && workSet.LastPow2K != BigInteger.Zero && k == (workSet.LastPow2K << 1))
@@ -1643,7 +1641,7 @@ internal static class BitContradictionSolverWithAMultiplier
for (i = 0; i < qOneOffsetsLength; i++) for (i = 0; i < qOneOffsetsLength; i++)
{ {
t = qOneOffsets[i]; t = qOneOffsets[i];
if (t < ForcedBits) if (t < ForcedALowBits)
{ {
// lastBit stand for lastByte here. We're reusing variable to limit registry pressure. // lastBit stand for lastByte here. We're reusing variable to limit registry pressure.
lastBit = t >> 3; lastBit = t >> 3;
@@ -1676,14 +1674,12 @@ internal static class BitContradictionSolverWithAMultiplier
qMod2k = new BigInteger(qMod2kBytes, isUnsigned: true, isBigEndian: false); qMod2k = new BigInteger(qMod2kBytes, isUnsigned: true, isBigEndian: false);
} }
Span<ulong> reversePrefix = stackalloc ulong[16]; ulong[] reversePrefix = workSet.LastQReverse;
GetReversePrefix1024(workSet, qPrefix, reversePrefix); GetReversePrefix1024(workSet, qPrefix, reversePrefix);
ulong[] lastPrefix = workSet.LastQPrefix; ulong[] lastPrefix = workSet.LastQPrefix;
ulong[] lastReverse = workSet.LastQReverse;
for (i = 0; i < 16; i++) for (i = 0; i < 16; i++)
{ {
lastPrefix[i] = qPrefix[i]; lastPrefix[i] = qPrefix[i];
lastReverse[i] = reversePrefix[i];
} }
workSet.HasLastQPrefix1024 = true; workSet.HasLastQPrefix1024 = true;
@@ -1743,7 +1739,7 @@ internal static class BitContradictionSolverWithAMultiplier
} }
int maxKnownA; int maxKnownA;
int maxFixed = maxAllowedA < ForcedBitsMinusOne ? maxAllowedA : ForcedBitsMinusOne; int maxFixed = maxAllowedA < (ForcedALowBits - 1) ? maxAllowedA : (ForcedALowBits - 1);
// wordValue is aLow word here. // wordValue is aLow word here.
if (maxFixed >= 0) if (maxFixed >= 0)
{ {
@@ -1810,7 +1806,7 @@ internal static class BitContradictionSolverWithAMultiplier
maxKnownA = maxFixed; maxKnownA = maxFixed;
} }
CarryRange carryLow; CarryRange carryLow = CarryRange.Zero;
// ------------------------------------------------------------ // ------------------------------------------------------------
// Cheap low-column prefilter (prefix-style): // Cheap low-column prefilter (prefix-style):
@@ -1819,9 +1815,8 @@ internal static class BitContradictionSolverWithAMultiplier
// we can propagate carry deterministically and reject immediately on contradiction. // we can propagate carry deterministically and reject immediately on contradiction.
// This is significantly cheaper than entering the full row-aware window DP. // This is significantly cheaper than entering the full row-aware window DP.
// ------------------------------------------------------------ // ------------------------------------------------------------
const int PrefilterColumns = 512; // 256..512 is a good trade-off; keep <= 1024 forced bits
// maxFixed now serves as preMax. // maxFixed now serves as preMax.
maxFixed = PrefilterColumns - 1; maxFixed = 512 - 1; // 256..512 is a good trade-off; keep <= 1024 forced bits
if (maxFixed > maxKnownA) if (maxFixed > maxKnownA)
{ {
maxFixed = maxKnownA; maxFixed = maxKnownA;
@@ -1837,14 +1832,11 @@ internal static class BitContradictionSolverWithAMultiplier
// Only run if we have at least a few columns to check. // Only run if we have at least a few columns to check.
if (maxFixed >= 8) if (maxFixed >= 8)
{ {
CarryRange preCarry = CarryRange.Zero;
Span<ulong> prefixMask = stackalloc ulong[16]; Span<ulong> prefixMask = stackalloc ulong[16];
// index is column here. We're reusing the variable to limit registry pressure. // index is column here. We're reusing the variable to limit registry pressure.
for (index = 0; index <= maxFixed; index++) for (index = 0; index <= maxFixed; index++)
{ {
// Required result bit for M_p in columns [0..p-1] is 1. // Required result bit for M_p in columns [0..p-1] is 1.
const int requiredBit = 1;
// Compute forced ones exactly: sum of a_{col - t} for all q_t=1 with t<=col. // Compute forced ones exactly: sum of a_{col - t} for all q_t=1 with t<=col.
forced = 0; forced = 0;
if (index <= 1023) if (index <= 1023)
@@ -1893,7 +1885,7 @@ internal static class BitContradictionSolverWithAMultiplier
} }
// remaining==0 here, so possible==forced. Propagate carry range deterministically. // remaining==0 here, so possible==forced. Propagate carry range deterministically.
if (!TryPropagateCarry(ref preCarry, forced, forced, requiredBit)) if (!TryPropagateCarry(ref carryLow, forced, forced, 1))
{ {
// reason = ContradictionReason.ParityUnreachable; // reason = ContradictionReason.ParityUnreachable;
divides = false; divides = false;
@@ -1903,17 +1895,7 @@ internal static class BitContradictionSolverWithAMultiplier
} }
// carryLow now serves as main bottom-up carry. // carryLow now serves as main bottom-up carry.
carryLow = CarryRange.Zero;
int topIndex0 = maxAllowedA;
int topIndex1 = maxAllowedA - 1;
bool top0KnownOne = topIndex0 == 0;
bool top1KnownOne = topIndex1 == 0;
// bool top0KnownZero = false;
// bool top1KnownZero = false;
int zeroTailStart = maxAllowedA + 1;
// long qHash = ComputeQOffsetsHash(qOneOffsets);
// if (!TryModularPrefilter(qOneOffsets, qHash, p, maxAllowedA)) // if (!TryModularPrefilter(qOneOffsets, qHash, p, maxAllowedA))
// { // {
@@ -1938,7 +1920,8 @@ internal static class BitContradictionSolverWithAMultiplier
} }
// Row-aware masks for q and a-window (supports q > 64 bits) // Row-aware masks for q and a-window (supports q > 64 bits)
ulong lastWordMask = (qBitLen & 63) == 0 ? ulong.MaxValue : ((bitMask64[qBitLen & 63]) - 1UL); // wordValue now holds lastWordMask.
wordValue = (qBitLen & 63) == 0 ? ulong.MaxValue : (bitMask64[qBitLen & 63] - 1UL);
// Initialize window for column 0: mark negative a indices as zero (t>0). // Initialize window for column 0: mark negative a indices as zero (t>0).
// Sliding window over a: bit t corresponds to a_{column - t}. // Sliding window over a: bit t corresponds to a_{column - t}.
ulong[] aOneWin = workSet.AOneWin; ulong[] aOneWin = workSet.AOneWin;
@@ -1958,10 +1941,9 @@ internal static class BitContradictionSolverWithAMultiplier
aZeroWin[0] |= 1UL; aZeroWin[0] |= 1UL;
} }
int lowColumn = 0; // index now serves as lowColumn.
index = 0;
int highColumn = pLong - 1; int highColumn = pLong - 1;
// carryLow now serves as main bottom-up carry.
carryLow = CarryRange.Zero;
// int bottomRunStart = 0; // int bottomRunStart = 0;
// int bottomRunEnd = 0; // int bottomRunEnd = 0;
@@ -2042,22 +2024,22 @@ internal static class BitContradictionSolverWithAMultiplier
// ----------------------------- // -----------------------------
// Continue full bottom-up DP for remaining columns // Continue full bottom-up DP for remaining columns
// ----------------------------- // -----------------------------
while (lowColumn <= highColumn) while (index <= highColumn)
{ {
int remaining = highColumn - lowColumn + 1; int remaining = highColumn - index + 1;
int blockSize = remaining < PingPongBlockColumns ? remaining : PingPongBlockColumns; int blockSize = remaining < PingPongBlockColumns ? remaining : PingPongBlockColumns;
#if DETAILED_LOG #if DETAILED_LOG
if (!TryProcessBottomUpBlockRowAware( if (!TryProcessBottomUpBlockRowAware(
qOneOffsets, qMaskWords, qWordCount, lastWordMask, maxAllowedA, qOneOffsets, qMaskWords, qWordCount, wordValue, maxAllowedA,
lowColumn, blockSize, index, blockSize,
ref carryLow, ref maxKnownA, ref segmentBase, ref carryLow, ref maxKnownA, ref segmentBase,
ref knownOne0, ref knownOne1, ref knownZero0, ref knownZero1, ref knownOne0, ref knownOne1, ref knownZero0, ref knownZero1,
windowSize, wordCount, aOneWin, aZeroWin, ref windowColumn, windowSize, wordCount, aOneWin, aZeroWin, ref windowColumn,
out reason)) out reason))
#else #else
if (!TryProcessBottomUpBlockRowAware( if (!TryProcessBottomUpBlockRowAware(
qOneOffsets, qMaskWords, qWordCount, lastWordMask, maxAllowedA, qOneOffsets, qMaskWords, qWordCount, wordValue, maxAllowedA,
lowColumn, blockSize, index, blockSize,
ref carryLow, ref maxKnownA, ref segmentBase, ref carryLow, ref maxKnownA, ref segmentBase,
ref knownOne0, ref knownOne1, ref knownZero0, ref knownZero1, ref knownOne0, ref knownOne1, ref knownZero0, ref knownZero1,
windowSize, aWordCount, aOneWin, aZeroWin, ref windowColumn)) windowSize, aWordCount, aOneWin, aZeroWin, ref windowColumn))
@@ -2070,7 +2052,7 @@ internal static class BitContradictionSolverWithAMultiplier
return true; return true;
} }
lowColumn += blockSize; index += blockSize;
} }
// long carryMin = carryLow.Min > carryHigh.Min ? carryLow.Min : carryHigh.Min; // long carryMin = carryLow.Min > carryHigh.Min ? carryLow.Min : carryHigh.Min;