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BitContradiction optimizations

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mlemanczyk committed 2026-01-12 02:45:46 +01:00
1 parent 2b803abcac
commit dc7a499f82
1 file changed
+162 -2
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PerfectNumbers.Core/ByDivisor/BitContradictionSolver.cs
+162 -2
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@@ -330,6 +330,22 @@ internal static class BitContradictionSolver
}
}
if (unknown == 0)
{
int requiredCarryParity = 1 ^ ((int)forced & 1);
long carryMin = AlignUpToParity(carry.Min, requiredCarryParity);
long carryMax = AlignDownToParity(carry.Max, requiredCarryParity);
if (carryMin > carryMax)
{
reason = ContradictionReason.ParityUnreachable;
return false;
}
carry = new CarryRange(carryMin, carryMax);
minSum = carry.Min;
maxSum = carry.Max;
}
minSum += forced;
maxSum += forced + unknown;
const int requiredParity = 1;
@@ -413,7 +429,8 @@ internal static class BitContradictionSolver
int windowEnd = qOneOffsetsLength;
long endColumn = startHighColumn - columnCount + 1;
for (long column = startHighColumn; column >= endColumn; column--)
long column = startHighColumn;
while (column >= endColumn)
{
// value is used as high column index
value = column;
@@ -441,6 +458,55 @@ internal static class BitContradictionSolver
// value is unknown bits count here
value = windowEnd - windowStart;
if (value == 0)
{
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
if (chunkEnd < endColumn)
{
chunkEnd = endColumn;
}
int steps = (int)(column - chunkEnd + 1);
if (steps > 1)
{
if (!AdvanceTopDownUnknown0(ref carryOutMin, ref carryOutMax, steps))
{
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
nextCarryOut = default;
return false;
}
column = chunkEnd - 1;
continue;
}
}
else if (value == 1)
{
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
if (chunkEnd < endColumn)
{
chunkEnd = endColumn;
}
int steps = (int)(column - chunkEnd + 1);
if (steps > 1)
{
if (!AdvanceTopDownUnknown1(ref carryOutMin, ref carryOutMax, steps))
{
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
nextCarryOut = default;
return false;
}
column = chunkEnd - 1;
continue;
}
}
// carryOutMin now becomes nextCarryMin to limit registry pressure
carryOutMin = (carryOutMin << 1) + 1 - value;
// carryOutMax now becomes nextCarryMax to limit registry pressure
@@ -461,6 +527,8 @@ internal static class BitContradictionSolver
nextCarryOut = default;
return false;
}
column--;
}
nextCarryOut = new CarryRange(carryOutMin, carryOutMax);
@@ -485,7 +553,8 @@ internal static class BitContradictionSolver
int windowStart = qOneOffsetsLength;
int windowEnd = qOneOffsetsLength;
for (long column = pLong - 1; column >= 0; column--)
long column = pLong - 1;
while (column >= 0)
{
// value is used as high column index
value = column;
@@ -513,6 +582,53 @@ internal static class BitContradictionSolver
// value is used as unknown bits count here
value = windowEnd - windowStart;
if (value == 0)
{
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
if (chunkEnd < 0)
{
chunkEnd = 0;
}
int steps = (int)(column - chunkEnd + 1);
if (steps > 1)
{
if (!AdvanceTopDownUnknown0(ref carryOutMin, ref carryOutMax, steps))
{
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
return false;
}
column = chunkEnd - 1;
continue;
}
}
else if (value == 1)
{
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
if (chunkEnd < 0)
{
chunkEnd = 0;
}
int steps = (int)(column - chunkEnd + 1);
if (steps > 1)
{
if (!AdvanceTopDownUnknown1(ref carryOutMin, ref carryOutMax, steps))
{
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
return false;
}
column = chunkEnd - 1;
continue;
}
}
// carryOutMin now becomes nextCarryMin to limit registry pressure
carryOutMin = (carryOutMin << 1) + 1 - value;
// carryOutMax now becomes nextCarryMax to limit registry pressure
@@ -532,6 +648,8 @@ internal static class BitContradictionSolver
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
return false;
}
column--;
}
if (carryOutMin > 0)
@@ -542,4 +660,46 @@ internal static class BitContradictionSolver
return true;
}
private static bool AdvanceTopDownUnknown1(ref long carryOutMin, ref long carryOutMax, int steps)
{
while (steps > 0)
{
int step = steps > 62 ? 62 : steps;
long pow = 1L << step;
if (carryOutMin > (long.MaxValue >> step) || carryOutMax > ((long.MaxValue - (pow - 1)) >> step))
{
carryOutMin = 0;
carryOutMax = long.MaxValue;
return true;
}
carryOutMin <<= step;
carryOutMax = (carryOutMax << step) + (pow - 1);
steps -= step;
}
return true;
}
private static bool AdvanceTopDownUnknown0(ref long carryOutMin, ref long carryOutMax, int steps)
{
while (steps > 0)
{
int step = steps > 62 ? 62 : steps;
if (carryOutMin > (long.MaxValue >> step) || carryOutMax > (long.MaxValue >> step))
{
carryOutMin = 0;
carryOutMax = long.MaxValue;
return true;
}
carryOutMin <<= step;
carryOutMax <<= step;
steps -= step;
}
return true;
}
}