mlemanczyk/even-perfect-numbers-scanner
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Implement multi-tier divisor cycle caching and per-thread reuse

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Marek Lemańczyk committed 2025-09-24 19:04:07 +02:00
1 parent e92bca197d
commit d4dcd0a534
8 files changed
+585 -145
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EvenPerfectBitScanner/Program.cs
+80 -34
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@@ -447,16 +447,18 @@ internal static class Program
}
Console.WriteLine($"Loading divisor cycles into memory...");
if (string.Equals(Path.GetExtension(cyclesPath), ".csv", StringComparison.OrdinalIgnoreCase))
{
MersenneDivisorCycles.Shared.LoadFrom(cyclesPath);
}
else
{
MersenneDivisorCycles.Shared.LoadFrom(cyclesPath);
}
if (string.Equals(Path.GetExtension(cyclesPath), ".csv", StringComparison.OrdinalIgnoreCase))
{
MersenneDivisorCycles.Shared.LoadFrom(cyclesPath);
}
else
{
MersenneDivisorCycles.Shared.LoadFrom(cyclesPath);
}
Console.WriteLine("Divisor cycles are ready");
DivisorCycleCache.Shared.ReloadFromCurrentSnapshot();
Console.WriteLine("Divisor cycles are ready");
if (useByDivisor)
{
@@ -882,12 +884,18 @@ internal static class Program
bool exhausted = false;
ulong divisor = 0UL;
int activeCount = 0;
Span<byte> hitsSpan = default;
int hitIndex = 0;
int index = 0;
Span<byte> hitsSpan = default;
int hitIndex = 0;
int index = 0;
bool useCycleFilter = _byDivisorTester!.UseDivisorCycles;
DivisorCycleCache.Lease cycleLease = default;
ulong cycleLeaseStart = 0UL;
ulong cycleLeaseEnd = 0UL;
ulong[]? cycleValues = null;
ulong divisorCycle = 0UL;
try
{
try
{
while (true)
{
if (Volatile.Read(ref remainingStates) == 0)
@@ -900,11 +908,11 @@ internal static class Program
divisor = AcquireNextDivisor(ref nextDivisor, divisorLimit, ref divisorsExhaustedFlag, ref finalDivisorBits, out exhausted, ref localDivisorCursor, ref localDivisorsRemaining);
if (divisor == 0UL)
{
if (!exhausted)
{
if (Volatile.Read(ref remainingStates) == 0)
if (divisor == 0UL)
{
if (!exhausted)
{
if (Volatile.Read(ref remainingStates) == 0)
{
break;
}
@@ -937,11 +945,48 @@ internal static class Program
break;
}
continue;
}
continue;
}
// Can we prepare as many buffers as many threads were requested upfront and have them prepared in separate task, so that they're always ready when needed?
activeCount = BuildPrimeBuffer(divisor, primeValues, allowedMaxValues, stateFlags, primeBuffer, indexBuffer, completionsBuffer, ref completionsCount, ref remainingStates, activeStateMask, ref activeStartIndex);
if (useCycleFilter)
{
if (!cycleLease.IsValid || divisor < cycleLeaseStart || divisor > cycleLeaseEnd)
{
cycleLease.Dispose();
cycleLease = DivisorCycleCache.Shared.Acquire(divisor);
cycleLeaseStart = cycleLease.Start;
cycleLeaseEnd = cycleLease.End;
cycleValues = cycleLease.Values;
}
else if (cycleValues is null)
{
cycleValues = cycleLease.Values;
}
if (cycleValues is not null && divisor >= cycleLeaseStart)
{
ulong offset = divisor - cycleLeaseStart;
if (offset < (ulong)cycleValues.Length)
{
divisorCycle = cycleValues[(int)offset];
}
else
{
divisorCycle = cycleLease.GetCycle(divisor);
}
}
else
{
divisorCycle = cycleLease.GetCycle(divisor);
}
}
else
{
divisorCycle = 0UL;
}
// Can we prepare as many buffers as many threads were requested upfront and have them prepared in separate task, so that they're always ready when needed?
activeCount = BuildPrimeBuffer(divisor, primeValues, allowedMaxValues, stateFlags, primeBuffer, indexBuffer, completionsBuffer, ref completionsCount, ref remainingStates, activeStateMask, ref activeStartIndex);
if (completionsCount > 0)
{
@@ -953,9 +998,9 @@ internal static class Program
continue;
}
hitsSpan = hitsBuffer.AsSpan(0, activeCount);
hitsSpan.Clear();
session.CheckDivisor(divisor, primeBuffer.AsSpan(0, activeCount), hitsSpan);
hitsSpan = hitsBuffer.AsSpan(0, activeCount);
hitsSpan.Clear();
session.CheckDivisor(divisor, divisorCycle, primeBuffer.AsSpan(0, activeCount), hitsSpan);
for (hitIndex = 0; hitIndex < activeCount; hitIndex++)
{
@@ -993,14 +1038,15 @@ internal static class Program
{
FlushPendingResults(compositesBuffer, ref compositesCount);
}
}
finally
{
ArrayPool<PendingResult>.Shared.Return(compositesBuffer, clearArray: true);
ArrayPool<PendingResult>.Shared.Return(completionsBuffer, clearArray: true);
ArrayPool<int>.Shared.Return(indexBuffer, clearArray: true);
ArrayPool<ulong>.Shared.Return(primeBuffer, clearArray: true);
ArrayPool<byte>.Shared.Return(hitsBuffer, clearArray: true);
}
finally
{
cycleLease.Dispose();
ArrayPool<PendingResult>.Shared.Return(compositesBuffer, clearArray: true);
ArrayPool<PendingResult>.Shared.Return(completionsBuffer, clearArray: true);
ArrayPool<int>.Shared.Return(indexBuffer, clearArray: true);
ArrayPool<ulong>.Shared.Return(primeBuffer, clearArray: true);
ArrayPool<byte>.Shared.Return(hitsBuffer, clearArray: true);
}
});
}