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Align heuristic prime testers with squared limits

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Marek Lemańczyk committed 2025-10-29 19:35:59 +01:00
1 parent 5536dc4865
commit f7a0627ce5
4 files changed
+109 -139
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PerfectNumbers.Core/HeuristicCombinedPrimeTester.cs
+57 -70
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@@ -152,36 +152,36 @@ public sealed class HeuristicCombinedPrimeTester
public static bool IsPrimeCpu(ulong n)
{
byte nMod10 = (byte)n.Mod10();
ulong sqrtLimit = ComputeHeuristicSqrt(n);
ulong maxDivisorSquare = ComputeHeuristicDivisorSquareLimit(n);
if (sqrtLimit < 3UL)
if (maxDivisorSquare < 9UL)
{
return EvaluateWithOpenNumericFallback(n);
}
return HeuristicTrialDivisionCpu(n, sqrtLimit, nMod10);
return HeuristicTrialDivisionCpu(n, maxDivisorSquare, nMod10);
}
public static bool IsPrimeGpu(ulong n)
{
byte nMod10 = (byte)n.Mod10();
ulong sqrtLimit = ComputeHeuristicSqrt(n);
return IsPrimeGpu(n, sqrtLimit, nMod10);
ulong maxDivisorSquare = ComputeHeuristicDivisorSquareLimit(n);
return IsPrimeGpu(n, maxDivisorSquare, nMod10);
}
public static bool IsPrimeGpu(ulong n, ulong sqrtLimit, byte nMod10)
public static bool IsPrimeGpu(ulong n, ulong maxDivisorSquare, byte nMod10)
{
// TODO: Is this condition ever met on the execution path in EvenPerfectBitScanner?
if (sqrtLimit < 3UL)
if (maxDivisorSquare < 9UL)
{
return EvaluateWithOpenNumericFallback(n);
}
bool compositeDetected = HeuristicTrialDivisionGpuDetectsDivisor(n, sqrtLimit, nMod10);
bool compositeDetected = HeuristicTrialDivisionGpuDetectsDivisor(n, maxDivisorSquare, nMod10);
return !compositeDetected;
}
private static bool HeuristicTrialDivisionCpu(ulong n, ulong sqrtLimit, byte nMod10)
private static bool HeuristicTrialDivisionCpu(ulong n, ulong maxDivisorSquare, byte nMod10)
{
ReadOnlySpan<uint> combinedDivisors = GetCombinedDivisors(nMod10);
ReadOnlySpan<ulong> combinedDivisorSquares = GetCombinedDivisorSquares(nMod10);
@@ -191,7 +191,7 @@ public sealed class HeuristicCombinedPrimeTester
for (int i = 0; i < length; i++)
{
ulong divisorSquare = combinedDivisorSquares[i];
if (divisorSquare > n)
if (divisorSquare > maxDivisorSquare)
{
break;
}
@@ -205,7 +205,7 @@ public sealed class HeuristicCombinedPrimeTester
return EvaluateWithOpenNumericFallback(n);
}
private static bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong sqrtLimit, byte nMod10)
private static bool HeuristicTrialDivisionGpuDetectsDivisor(ulong n, ulong maxDivisorSquare, byte nMod10)
{
int batchCapacity = HeuristicGpuDivisorBatchSize;
var divisorPool = ThreadStaticPools.UlongPool;
@@ -243,7 +243,7 @@ public sealed class HeuristicCombinedPrimeTester
for (int i = 0; i < length; i++)
{
ulong divisorSquare = combinedDivisorSquares[i];
if (divisorSquare > n)
if (divisorSquare > maxDivisorSquare)
{
break;
}
@@ -282,29 +282,10 @@ Cleanup:
{
return Prime.Numbers.IsPrime(n);
}
internal static ulong ComputeHeuristicSqrt(ulong n)
{
ulong sqrt = (ulong)Math.Sqrt(n);
UInt128 square = (UInt128)sqrt * sqrt;
while (square > n)
{
sqrt--;
square = (UInt128)sqrt * sqrt;
}
ulong next = sqrt + 1UL;
UInt128 nextSquare = (UInt128)next * next;
while (nextSquare <= n)
{
sqrt = next;
next++;
nextSquare = (UInt128)next * next;
}
return sqrt;
}
internal static ulong ComputeHeuristicDivisorSquareLimit(ulong n)
{
return n;
}
private static ReadOnlySpan<uint> GetCombinedDivisors(byte nMod10)
{
@@ -514,9 +495,9 @@ Cleanup:
};
[MethodImpl(MethodImplOptions.AggressiveInlining)]
internal static HeuristicDivisorEnumerator CreateHeuristicDivisorEnumerator(ulong sqrtLimit, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
internal static HeuristicDivisorEnumerator CreateHeuristicDivisorEnumerator(ulong maxDivisorSquare, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
{
return new HeuristicDivisorEnumerator(sqrtLimit, nMod10, groupBBuffer);
return new HeuristicDivisorEnumerator(maxDivisorSquare, nMod10, groupBBuffer);
}
internal struct HeuristicGroupBSequenceState
@@ -597,44 +578,50 @@ Cleanup:
}
internal ref struct HeuristicDivisorEnumerator
{
private readonly ulong sqrtLimit;
private readonly ReadOnlySpan<uint> combinedDivisors;
private int index;
{
private readonly ulong maxDivisorSquare;
private readonly ReadOnlySpan<uint> combinedDivisors;
private readonly ReadOnlySpan<ulong> combinedDivisorSquares;
private int index;
public HeuristicDivisorEnumerator(ulong sqrtLimit, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
{
this.sqrtLimit = sqrtLimit;
_ = groupBBuffer;
combinedDivisors = GetCombinedDivisors(nMod10);
index = 0;
}
public HeuristicDivisorEnumerator(ulong maxDivisorSquare, byte nMod10, Span<HeuristicGroupBSequenceState> groupBBuffer)
{
this.maxDivisorSquare = maxDivisorSquare;
_ = groupBBuffer;
combinedDivisors = GetCombinedDivisors(nMod10);
combinedDivisorSquares = GetCombinedDivisorSquares(nMod10);
index = 0;
}
public bool TryGetNext(out HeuristicDivisorCandidate candidate)
{
while (index < combinedDivisors.Length)
{
uint entry = combinedDivisors[index++];
if (entry > sqrtLimit)
{
index = combinedDivisors.Length;
break;
}
public bool TryGetNext(out HeuristicDivisorCandidate candidate)
{
while (index < combinedDivisors.Length)
{
int currentIndex = index;
ulong divisorSquare = combinedDivisorSquares[currentIndex];
if (divisorSquare > maxDivisorSquare)
{
index = combinedDivisors.Length;
break;
}
HeuristicDivisorGroup group = ResolveGroup(entry);
ulong value = entry;
byte ending = (byte)(value % 10UL);
ushort residue = (ushort)(value % Wheel210);
candidate = new HeuristicDivisorCandidate(value, group, ending, 0, residue);
return true;
}
uint entry = combinedDivisors[currentIndex];
index = currentIndex + 1;
candidate = default;
return false;
}
}
HeuristicDivisorGroup group = ResolveGroup(entry);
ulong value = entry;
byte ending = (byte)(value % 10UL);
ushort residue = (ushort)(value % Wheel210);
candidate = new HeuristicDivisorCandidate(value, group, ending, 0, residue);
return true;
}
internal ref struct MersenneHeuristicDivisorEnumerator
candidate = default;
return false;
}
}
internal ref struct MersenneHeuristicDivisorEnumerator
{
private readonly GpuUInt128 step;
private readonly GpuUInt128 limit;