mlemanczyk/even-perfect-numbers-scanner
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Additional logging added.

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mlemanczyk committed 2025-10-26 20:00:32 +01:00
1 parent 5c9fb47a3d
commit f2ce40ade9
3 files changed
+123 -74
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PerfectNumbers.Core/MersenneDivisorCycles.cs
+71 -63
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@@ -360,79 +360,81 @@ public class MersenneDivisorCycles
return true;
}
private static bool TryFactorIntoCountsInternal(ulong value, Dictionary<ulong, int> counts)
{
// The EvenPerfectBitScanner only requests factors for values >= 2 here. Leave the guard documented without executing it.
// if (value <= 1UL)
// {
// return true;
// }
// private static ulong _tryFactorIntoCountsInternalHits;
// private static ulong _tryCalculateCycleLengthHeuristicHits;
ulong remaining = value;
uint[] smallPrimes = PrimesGenerator.SmallPrimes;
ulong[] smallPrimesSquared = PrimesGenerator.SmallPrimesPow2;
int smallLength = smallPrimes.Length;
private static bool TryFactorIntoCountsInternal(ulong value, Dictionary<ulong, int> counts)
{
// The EvenPerfectBitScanner only requests factors for values >= 2 here. Leave the guard documented without executing it.
// if (value <= 1UL)
// {
// return true;
// }
for (int i = 0; i < smallLength; i++)
{
ulong prime = smallPrimes[i];
if (smallPrimesSquared[i] > remaining)
{
break;
}
ulong remaining = value;
uint[] smallPrimes = PrimesGenerator.SmallPrimes;
ulong[] smallPrimesSquared = PrimesGenerator.SmallPrimesPow2;
int smallLength = smallPrimes.Length;
// TODO: Reuse the remainder-tracking update from the cycle heuristic so repeated divisions disappear from this loop.
while ((remaining % prime) == 0UL)
{
AddFactor(counts, prime);
remaining /= prime;
}
}
for (int i = 0; i < smallLength; i++)
{
ulong prime = smallPrimes[i];
if (smallPrimesSquared[i] > remaining)
{
break;
}
if (remaining == 1UL)
{
return true;
}
// TODO: Reuse the remainder-tracking update from the cycle heuristic so repeated divisions disappear from this loop.
while ((remaining % prime) == 0UL)
{
AddFactor(counts, prime);
remaining /= prime;
}
}
// TODO: Benchmark PrimeTester.IsPrimeCpu against Open.Numeric.Primes on the EvenPerfectBitScanner workloads to confirm the faster option for wide composites.
// if (HeuristicPrimeTester.Exclusive.IsPrimeCpu(remaining, CancellationToken.None))
if (PrimeTester.IsPrimeCpu(remaining, CancellationToken.None))
{
AddFactor(counts, remaining);
return true;
}
// TODO: Benchmark PrimeTester.IsPrimeInternal against Open.Numeric.Primes on the EvenPerfectBitScanner workloads to confirm the faster option for wide composites.
// if (HeuristicPrimeTester.Exclusive.IsPrime(remaining, CancellationToken.None))
// TODO: Evaluate folding the remainder-tracking mechanism into PollardRho64 so the walk leverages previously computed residues.
ulong factor = PollardRho64(remaining);
if (factor == 0UL || factor == remaining)
{
// Pollard-Rho can still stall on rare stubborn composites during test and benchmark runs, so keep the failure guard in place
// and let the caller fall back to the cached cycle calculator.
return false;
}
// Atomic.Add(ref _tryFactorIntoCountsInternalHits, 1UL);
// Console.WriteLine($"MersenneDivisorCycles.TryFactorIntoCountsInternal hits {Volatile.Read(ref _tryFactorIntoCountsInternalHits)}");
// TODO: Investigate computing this quotient via remainder tracking or reciprocal multiplication to avoid the division.
ulong quotient = remaining / factor;
// Pollard-Rho never returns factors <= 1 on the EvenPerfectBitScanner path; keep the old guard documented
// for completeness without branching in the hot path.
// if (factor > 1UL && !TryFactorIntoCountsInternal(factor, counts))
// {
// return false;
// }
if (PrimeTester.IsPrimeCpu(remaining, CancellationToken.None))
{
AddFactor(counts, remaining);
return true;
}
if (!TryFactorIntoCountsInternal(factor, counts))
{
return false;
}
// TODO: Evaluate folding the remainder-tracking mechanism into PollardRho64 so the walk leverages previously computed residues.
ulong factor = PollardRho64(remaining);
if (factor == 0UL || factor == remaining)
{
// Pollard-Rho can still stall on rare stubborn composites during test and benchmark runs, so keep the failure guard in place
// and let the caller fall back to the cached cycle calculator.
return false;
}
// Guard the recursive calls to terminate once Pollard-Rho reduces either branch to 1.
if (quotient > 1UL && !TryFactorIntoCountsInternal(quotient, counts))
{
return false;
}
// TODO: Investigate computing this quotient via remainder tracking or reciprocal multiplication to avoid the division.
ulong quotient = remaining / factor;
// Pollard-Rho never returns factors <= 1 on the EvenPerfectBitScanner path; keep the old guard documented
// for completeness without branching in the hot path.
// if (factor > 1UL && !TryFactorIntoCountsInternal(factor, counts))
// {
// return false;
// }
return true;
}
if (!TryFactorIntoCountsInternal(factor, counts))
{
return false;
}
// Guard the recursive calls to terminate once Pollard-Rho reduces either branch to 1.
if (quotient > 1UL && !TryFactorIntoCountsInternal(quotient, counts))
{
return false;
}
return true;
}
private static void AddFactor(Dictionary<ulong, int> counts, ulong factor)
{
@@ -928,6 +930,12 @@ public class MersenneDivisorCycles
return true;
}
// if (!skipPrimeOrderHeuristic)
// {
// Atomic.Add(ref _tryCalculateCycleLengthHeuristicHits, 1UL);
// Console.WriteLine($"MersenneDivisorCycles.CalculateCycleLengthFallback hits {Volatile.Read(ref _tryCalculateCycleLengthHeuristicHits)}");
// }
// if (!skipPrimeOrderHeuristic && HeuristicPrimeTester.Exclusive.IsPrimeCpu(divisor, CancellationToken.None))
if (!skipPrimeOrderHeuristic && PrimeTester.IsPrimeCpu(divisor, CancellationToken.None))
{