mlemanczyk/even-perfect-numbers-scanner
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Performance improvement and debug console output added.

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Marek Lemańczyk committed 2025-10-04 01:06:44 +02:00
1 parent 4f18a02b02
commit c27673ed38
2 files changed
+109 -27
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PerfectNumbers.Core/PrimeOrderCalculator.cs
+76 -7
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@@ -54,7 +54,7 @@ internal static class PrimeOrderCalculator
public PrimeOrderMode Mode { get; }
public static PrimeOrderSearchConfig HeuristicDefault => new(100_000, 1, 24, PrimeOrderMode.Heuristic);
public static PrimeOrderSearchConfig HeuristicDefault => new(100_000, 128, 24, PrimeOrderMode.Heuristic);
public static PrimeOrderSearchConfig StrictDefault => new(1_000_000, 0, 0, PrimeOrderMode.Strict);
}
@@ -69,26 +69,36 @@ internal static class PrimeOrderCalculator
ulong phi = prime - 1UL;
MontgomeryDivisorData divisorData = MontgomeryDivisorDataCache.Get(prime);
#if DEBUG
Console.WriteLine("Partial factoring φ(p)");
#endif
PartialFactorResult phiFactors = PartialFactor(phi, config);
if (phiFactors.Factors is null)
{
#if DEBUG
Console.WriteLine("No factors found");
#endif
return FinishStrictly(prime, config.Mode);
}
#if DEBUG
Console.WriteLine("Trying special max check");
#endif
if (phiFactors.FullyFactored && TrySpecialMax(phi, prime, phiFactors, divisorData))
{
return new PrimeOrderResult(PrimeOrderStatus.Found, phi);
}
#if DEBUG
Console.WriteLine("Initializing starting order");
#endif
ulong candidateOrder = InitializeStartingOrder(prime, phi, divisorData);
candidateOrder = ExponentLowering(candidateOrder, prime, phiFactors, divisorData);
#if DEBUG
Console.WriteLine("Trying to confirm order");
#endif
if (TryConfirmOrder(prime, candidateOrder, divisorData, config))
{
return new PrimeOrderResult(PrimeOrderStatus.Found, candidateOrder);
@@ -104,6 +114,9 @@ internal static class PrimeOrderCalculator
return new PrimeOrderResult(PrimeOrderStatus.Found, order);
}
#if DEBUG
Console.WriteLine("Heuristic unresolved, finishing strictly");
#endif
return FinishStrictly(prime, config.Mode);
}
@@ -156,7 +169,9 @@ internal static class PrimeOrderCalculator
Span<FactorEntry> buffer = tempArray;
factorSpan.CopyTo(buffer);
if (!factors.FullyFactored && factors.Cofactor > 1UL && PrimeTester.IsPrimeInternal(factors.Cofactor, CancellationToken.None))
bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factors.Cofactor);
// bool isPrime = PrimeTester.IsPrimeInternal(factors.Cofactor, CancellationToken.None);
if (!factors.FullyFactored && factors.Cofactor > 1UL && isPrime)
{
buffer[length] = new FactorEntry(factors.Cofactor, 1);
length++;
@@ -205,13 +220,18 @@ internal static class PrimeOrderCalculator
}
// Calculating `a^order ≡ 1 (mod p)` is a prerequisite for `order` being the actual order of 2 modulo `p`.
#if DEBUG
Console.WriteLine("Verifying a^order ≡ 1 (mod p)");
#endif
if (order.Pow2MontgomeryModWindowed(divisorData, keepMontgomery: false) != 1UL)
{
return false;
}
#if DEBUG
Console.WriteLine("Partial factoring order");
#endif
// TODO: Do we do partial factoring of order multiple times?
PartialFactorResult factorization = PartialFactor(order, config);
if (factorization.Factors is null)
@@ -223,23 +243,33 @@ internal static class PrimeOrderCalculator
{
if (factorization.Cofactor <= 1UL)
{
#if DEBUG
Console.WriteLine("Cofactor <= 1. No factors found");
#endif
return false;
}
// TODO: Use Open.Numerics.Primality for this final check once it's available.
#if DEBUG
Console.WriteLine("Cofactor > 1. Testing primality of cofactor");
if (!PrimeTester.IsPrimeInternal(factorization.Cofactor, CancellationToken.None))
#endif
bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factorization.Cofactor);
// bool isPrime = PrimeTester.IsPrimeInternal(factorization.Cofactor, CancellationToken.None);
if (!isPrime)
{
return false;
}
#if DEBUG
Console.WriteLine("Adding cofactor as prime factor");
#endif
factorization = factorization.WithAdditionalPrime(factorization.Cofactor);
}
ReadOnlySpan<FactorEntry> span = factorization.Factors;
#if DEBUG
Console.WriteLine("Verifying prime-power reductions");
#endif
int length = factorization.Count;
for (int i = 0; i < length; i++)
{
@@ -279,7 +309,9 @@ internal static class PrimeOrderCalculator
}
// TODO: Do we do partial factoring of order multiple times?
#if DEBUG
Console.WriteLine("Trying heuristic. Partial factoring order");
#endif
PartialFactorResult orderFactors = PartialFactor(order, config);
if (orderFactors.Factors is null)
{
@@ -293,7 +325,9 @@ internal static class PrimeOrderCalculator
return false;
}
if (!PrimeTester.IsPrimeInternal(orderFactors.Cofactor, CancellationToken.None))
var isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(orderFactors.Cofactor);
// if (!PrimeTester.IsPrimeInternal(orderFactors.Cofactor, CancellationToken.None))
if (!isPrime)
{
return false;
}
@@ -304,17 +338,27 @@ internal static class PrimeOrderCalculator
int capacity = config.MaxPowChecks <= 0 ? 64 : config.MaxPowChecks * 4;
List<ulong> candidates = new(capacity);
FactorEntry[] factorArray = orderFactors.Factors!;
#if DEBUG
Console.WriteLine("Building candidates list");
#endif
BuildCandidates(order, factorArray, orderFactors.Count, candidates, capacity);
if (candidates.Count == 0)
{
return false;
}
#if DEBUG
Console.WriteLine("Sorting candidates");
#endif
SortCandidates(prime, previousOrder, candidates);
int powBudget = config.MaxPowChecks <= 0 ? candidates.Count : config.MaxPowChecks;
int powUsed = 0;
int candidateCount = candidates.Count;
#if DEBUG
Console.WriteLine($"Checking candidates ({candidateCount} candidates, {powBudget} pow budget)");
#endif
for (int i = 0; i < candidateCount; i++)
{
if (powUsed >= powBudget)
@@ -339,6 +383,9 @@ internal static class PrimeOrderCalculator
return true;
}
#if DEBUG
Console.WriteLine("No candidate confirmed");
#endif
return false;
}
@@ -524,7 +571,9 @@ internal static class PrimeOrderCalculator
return false;
}
if (!PrimeTester.IsPrimeInternal(factorization.Cofactor, CancellationToken.None))
bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factorization.Cofactor);
// bool isPrime = PrimeTester.IsPrimeInternal(factorization.Cofactor, CancellationToken.None);
if (!isPrime)
{
return false;
}
@@ -579,6 +628,10 @@ internal static class PrimeOrderCalculator
for (int i = 0; i < primeCount; i++)
{
uint primeCandidate = primes[i];
#if DEBUG
Console.WriteLine($"Trying small prime {primeCandidate}");
#endif
if (primeCandidate > limit)
{
break;
@@ -614,6 +667,9 @@ internal static class PrimeOrderCalculator
if (config.PollardRhoMilliseconds > 0 && pending.Count > 0)
{
#if DEBUG
Console.WriteLine("Processing pending composites with Pollard's Rho");
#endif
Stopwatch stopwatch = Stopwatch.StartNew();
long budgetTicks = TimeSpan.FromMilliseconds(config.PollardRhoMilliseconds).Ticks;
Stack<ulong> stack = new();
@@ -628,7 +684,9 @@ internal static class PrimeOrderCalculator
continue;
}
if (PrimeTester.IsPrimeInternal(composite, CancellationToken.None))
bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
// if (PrimeTester.IsPrimeInternal(composite, CancellationToken.None))
if (isPrime)
{
AddFactor(counts, composite, 1);
continue;
@@ -654,10 +712,15 @@ internal static class PrimeOrderCalculator
ulong cofactor = 1UL;
int pendingCount = pending.Count;
#if DEBUG
Console.WriteLine($"Processing {pendingCount} pending composites with Open.Numeric.Primes");
#endif
for (int i = 0; i < pendingCount; i++)
{
ulong composite = pending[i];
if (PrimeTester.IsPrimeInternal(composite, CancellationToken.None))
bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(composite);
// if (PrimeTester.IsPrimeInternal(composite, CancellationToken.None))
if (isPrime)
{
AddFactor(counts, composite, 1);
}
@@ -669,11 +732,17 @@ internal static class PrimeOrderCalculator
if (counts.Count == 0 && cofactor == value)
{
#if DEBUG
Console.WriteLine("cofactor is the same as value, no factors found");
#endif
return new PartialFactorResult(null, value, false, 0);
}
FactorEntry[] factors = ArrayPool<FactorEntry>.Shared.Rent(counts.Count);
int index = 0;
#if DEBUG
Console.WriteLine($"Collecting {counts.Count} prime factors");
#endif
foreach (KeyValuePair<ulong, int> entry in counts)
{
factors[index] = new FactorEntry(entry.Key, entry.Value);