mlemanczyk/even-perfect-numbers-scanner
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Initialize cycle remainder stepping upfront

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Marek Lemańczyk committed 2025-09-25 21:09:28 +02:00
1 parent 699612f4f9
commit 9958338820
3 files changed
+76 -77
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PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs
+14 -3
View File
@@ -307,7 +307,13 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
return;
}
bool cycleEnabled = _owner._useDivisorCycles && divisorCycle != 0UL;
bool useDivisorCycles = _owner._useDivisorCycles;
if (useDivisorCycles && divisorCycle == 0UL)
{
throw new InvalidOperationException($"Missing divisor cycle for divisor {divisor}.");
}
bool cycleEnabled = useDivisorCycles;
MontgomeryDivisorData divisorData = MontgomeryDivisorDataCache.Get(divisor);
var exponentStepper = new ExponentRemainderStepper(divisorData);
@@ -321,9 +327,14 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
{
var stepper = new CycleRemainderStepper(divisorCycle);
for (int i = 0; i < length; i++)
ulong remainder = stepper.Initialize(primes[0]);
hits[0] = remainder == 0UL
? (exponentStepper.ComputeNextIsUnity(primes[0]) ? (byte)1 : (byte)0)
: (byte)0;
for (int i = 1; i < length; i++)
{
ulong remainder = stepper.ComputeNext(primes[i]);
remainder = stepper.ComputeNext(primes[i]);
if (remainder != 0UL)
{
hits[i] = 0;
PerfectNumbers.Core/CycleRemainderStepper.cs
+41 -36
View File
@@ -1,3 +1,4 @@
using System;
using System.Numerics;
namespace PerfectNumbers.Core;
@@ -11,14 +12,17 @@ internal struct CycleRemainderStepper
public CycleRemainderStepper(ulong cycleLength)
{
if (cycleLength == 0UL)
{
throw new ArgumentOutOfRangeException(nameof(cycleLength), "Cycle length must be non-zero.");
}
_cycleLength = cycleLength;
_previousPrime = 0UL;
_currentRemainder = 0UL;
_hasState = false;
}
public bool HasCycle => _cycleLength != 0UL;
public void Reset()
{
_previousPrime = 0UL;
@@ -26,52 +30,53 @@ internal struct CycleRemainderStepper
_hasState = false;
}
public void InitializeState(ulong previousPrime, ulong previousRemainder, bool hasState)
public ulong Initialize(ulong prime)
{
_previousPrime = previousPrime;
_currentRemainder = previousRemainder;
_hasState = hasState;
ulong cycleLength = _cycleLength;
ulong remainder = prime;
if (remainder >= cycleLength)
{
remainder %= cycleLength;
}
_previousPrime = prime;
_currentRemainder = remainder;
_hasState = true;
return remainder;
}
public ulong ComputeNext(ulong prime)
{
if (_cycleLength == 0UL)
if (!_hasState)
{
_previousPrime = prime;
_currentRemainder = 0UL;
_hasState = true;
return 0UL;
throw new InvalidOperationException("CycleRemainderStepper must be initialized before computing.");
}
if (!_hasState || prime <= _previousPrime)
if (prime <= _previousPrime)
{
_currentRemainder = prime % _cycleLength;
_hasState = true;
}
else
{
ulong delta = prime - _previousPrime;
if (ulong.MaxValue - _currentRemainder < delta)
{
UInt128 extended = (UInt128)_currentRemainder + delta;
_currentRemainder = (ulong)(extended % _cycleLength);
}
else
{
_currentRemainder += delta;
if (_currentRemainder >= _cycleLength)
{
_currentRemainder -= _cycleLength;
if (_currentRemainder >= _cycleLength)
{
_currentRemainder %= _cycleLength;
}
}
}
throw new ArgumentOutOfRangeException(nameof(prime), "Primes must be processed in strictly increasing order.");
}
ulong cycleLength = _cycleLength;
ulong delta = prime - _previousPrime;
_previousPrime = prime;
if (ulong.MaxValue - _currentRemainder < delta)
{
UInt128 extended = (UInt128)_currentRemainder + delta;
_currentRemainder = (ulong)(extended % cycleLength);
return _currentRemainder;
}
_currentRemainder += delta;
if (_currentRemainder >= cycleLength)
{
_currentRemainder -= cycleLength;
if (_currentRemainder >= cycleLength)
{
_currentRemainder %= cycleLength;
}
}
return _currentRemainder;
}
PerfectNumbers.Core/Gpu/MersenneNumberDivisorByDivisorGpuTester.cs
+21 -38
View File
@@ -391,8 +391,6 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
return;
}
EnsureCapacity(gpuBatchSize);
MontgomeryDivisorData divisorData = MontgomeryDivisorDataCache.Get(divisor);
var exponentStepper = new ExponentRemainderStepper(divisorData);
if (!exponentStepper.IsValidModulus)
@@ -407,7 +405,15 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
throw new InvalidOperationException($"Missing divisor cycle for divisor {divisor}.");
}
CycleRemainderStepper cycleStepper = useDivisorCycles ? new CycleRemainderStepper(divisorCycle) : default;
CycleRemainderStepper cycleStepper = default;
ulong initialCycleRemainder = 0UL;
bool cycleRemainderPending = false;
if (useDivisorCycles)
{
cycleStepper = new CycleRemainderStepper(divisorCycle);
initialCycleRemainder = cycleStepper.Initialize(primes[0]);
cycleRemainderPending = true;
}
Accelerator accelerator = _accelerator;
Action<Index1D, MontgomeryDivisorData, ArrayView<ulong>, ArrayView<ulong>> kernel = _kernel;
@@ -437,7 +443,16 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
if (useDivisorCycles)
{
ulong remainder = cycleStepper.ComputeNext(primeValue);
ulong remainder;
if (cycleRemainderPending)
{
remainder = initialCycleRemainder;
cycleRemainderPending = false;
}
else
{
remainder = cycleStepper.ComputeNext(primeValue);
}
if (remainder != 0UL)
{
continue;
@@ -507,43 +522,11 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
}
}
private void EnsureCapacity(int requiredCapacity)
public void Dispose()
{
if (requiredCapacity <= _capacity)
if (_disposed)
{
return;
}
_exponentsBuffer.Dispose();
_resultsBuffer.Dispose();
ArrayPool<ulong>.Shared.Return(_hostBuffer, clearArray: false);
ArrayPool<int>.Shared.Return(_positionBuffer, clearArray: false);
ArrayPool<byte>.Shared.Return(_modeBuffer, clearArray: false);
int newCapacity = _capacity;
if (newCapacity < 1)
{
newCapacity = 1;
}
while (newCapacity < requiredCapacity)
{
newCapacity <<= 1;
}
_exponentsBuffer = _accelerator.Allocate1D<ulong>(newCapacity);
_resultsBuffer = _accelerator.Allocate1D<ulong>(newCapacity);
_hostBuffer = ArrayPool<ulong>.Shared.Rent(newCapacity);
_positionBuffer = ArrayPool<int>.Shared.Rent(newCapacity);
_modeBuffer = ArrayPool<byte>.Shared.Rent(newCapacity);
_capacity = newCapacity;
}
public void Dispose()
{
if (_disposed)
{
return;
}
_disposed = true;