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Revert "Merge pull request #24 from mlemanczyk/codex/modify-evenperfectbitscanner-for-residue-mode"

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This reverts commit 2d024cc708, reversing
changes made to b1c29ad16e.
This commit is contained in:
Marek Lemańczyk committed 2025-09-21 02:25:18 +02:00
1 parent deb25796a8
commit 8a6fc0c6a5
7 files changed
+265 -551
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PerfectNumbers.Core/MersenneNumberTester.cs
+62 -150
View File
@@ -16,28 +16,26 @@ public enum GpuKernelType
}
public sealed class MersenneNumberTester(
bool useIncremental = true,
bool useOrderCache = false,
GpuKernelType kernelType = GpuKernelType.Incremental,
bool useModuloWorkaround = false,
bool useOrder = false,
bool useGpuLucas = true,
bool useGpuScan = true,
bool useGpuOrder = true,
bool useResidue = true,
UInt128? maxK = null,
UInt128? residueDivisorSets = null)
bool useIncremental = true,
bool useOrderCache = false,
GpuKernelType kernelType = GpuKernelType.Incremental,
bool useModuloWorkaround = false,
bool useOrder = false,
bool useGpuLucas = true,
bool useGpuScan = true,
bool useGpuOrder = true,
bool useResidue = true,
ulong maxK = 5_000_000UL)
{
private readonly bool _useResidue = useResidue;
private readonly bool _useIncremental = useIncremental && !useResidue;
private readonly UInt128 _maxK = maxK ?? (UInt128)5_000_000UL;
private readonly UInt128 _residueDivisorSetCount = residueDivisorSets ?? (UInt128)PerfectNumberConstants.ExtraDivisorCycleSearchLimit;
private readonly bool _useResidue = useResidue;
private readonly bool _useIncremental = useIncremental && !useResidue;
private readonly ulong _maxK = maxK;
private readonly GpuKernelType _kernelType = kernelType;
private readonly bool _useModuloWorkaround = useModuloWorkaround;
private readonly bool _useGpuLucas = useGpuLucas;
private readonly bool _useGpuScan = useGpuScan; // device for pow2mod/incremental scanning
private readonly bool _useGpuOrder = useGpuOrder; // device for order computations
private static readonly ConcurrentDictionary<UInt128, ulong> OrderCache = new();
private readonly bool _useModuloWorkaround = useModuloWorkaround;
private readonly bool _useGpuLucas = useGpuLucas;
private readonly bool _useGpuScan = useGpuScan; // device for pow2mod/incremental scanning
private readonly bool _useGpuOrder = useGpuOrder; // device for order computations
private static readonly ConcurrentDictionary<UInt128, ulong> OrderCache = new();
private readonly MersenneNumberIncrementalGpuTester _incrementalGpuTester = new(kernelType, useGpuOrder);
private readonly MersenneNumberIncrementalCpuTester _incrementalCpuTester = new(kernelType);
private readonly MersenneNumberOrderGpuTester _orderGpuTester = new(kernelType, useGpuOrder);
@@ -50,24 +48,7 @@ public sealed class MersenneNumberTester(
// TODO: Ensure Program passes useResidue correctly and that residue-vs-incremental-vs-LL selection respects CLI flags.
// Also consider injecting a shared cycles cache (MersenneDivisorCycles.Shared) to both CPU and GPU testers.
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static UInt128 DivideRoundUp(UInt128 value, UInt128 divisor)
{
if (divisor == UInt128.Zero)
{
return UInt128.Zero;
}
UInt128 result = value / divisor;
if (result * divisor == value)
{
return result;
}
return result + UInt128.One;
}
public void WarmUpOrders(ulong exponent, ulong limit = 5_000_000UL)
public void WarmUpOrders(ulong exponent, ulong limit = 5_000_000UL)
{
bool cacheEnabled = useOrderCache;
if (!cacheEnabled)
@@ -218,116 +199,51 @@ public sealed class MersenneNumberTester(
}
}
public bool IsMersennePrime(ulong exponent) => IsMersennePrime(exponent, out _);
public bool IsMersennePrime(ulong exponent)
{
// Safe early rejections using known orders for tiny primes:
// 7 | M_p iff 3 | p. Avoid rejecting p == 3 where M_3 == 7 is prime.
if ((exponent % 3UL) == 0UL && exponent != 3UL)
{
return false;
}
public bool IsMersennePrime(ulong exponent, out bool divisorsExhausted)
{
divisorsExhausted = false;
if ((exponent & 3UL) == 1UL && exponent.SharesFactorWithExponentMinusOne())
{
return false;
}
// Safe early rejections using known orders for tiny primes:
// 7 | M_p iff 3 | p. Avoid rejecting p == 3 where M_3 == 7 is prime.
if ((exponent % 3UL) == 0UL && exponent != 3UL)
{
divisorsExhausted = true;
return false;
}
if ((exponent & 3UL) == 1UL && exponent.SharesFactorWithExponentMinusOne())
{
divisorsExhausted = true;
return false;
}
// Skip even exponents: for even p > 2, M_p is composite; here p is large.
if ((exponent & 1UL) == 0UL)
{
divisorsExhausted = true;
return false;
}
// Skip even exponents: for even p > 2, M_p is composite; here p is large.
if ((exponent & 1UL) == 0UL)
{
return false;
}
bool prePrime = true;
UInt128 twoP = (UInt128)exponent << 1; // 2 * p
// UInt128 maxDivisor = new(ulong.MaxValue, ulong.MaxValue);
UInt128 maxK = UInt128Numbers.Two.Pow(exponent) / 2 + 1;
bool lastIsSeven = (exponent & 3UL) == 3UL;
UInt128 twoP = (UInt128)exponent << 1; // 2 * p
// UInt128 maxDivisor = new(ulong.MaxValue, ulong.MaxValue);
UInt128 maxK = UInt128Numbers.Two.Pow(exponent) / 2 + 1;
bool lastIsSeven = (exponent & 3UL) == 3UL;
// In residue mode the residue scan is the final primality check.
if (_useResidue)
{
if (_maxK < maxK)
{
maxK = _maxK;
}
// In residue mode the residue scan is the final primality check.
if (_useResidue)
{
if ((UInt128)_maxK < maxK)
{
maxK = _maxK;
}
if (_maxK == UInt128.Zero || _residueDivisorSetCount == UInt128.Zero)
{
return prePrime;
}
if (_useGpuScan)
{
_residueGpuTester!.Scan(exponent, twoP, lastIsSeven, maxK, ref prePrime);
}
else
{
_residueCpuTester!.Scan(exponent, twoP, lastIsSeven, maxK, ref prePrime);
}
UInt128 totalLimit = _maxK;
if (totalLimit > maxK)
{
totalLimit = maxK;
}
if (totalLimit == UInt128.Zero)
{
return true;
}
UInt128 requestedSets = _residueDivisorSetCount;
if (_useGpuScan)
{
UInt128 maxUsefulSets = DivideRoundUp(totalLimit, (UInt128)GpuConstants.ScanBatchSize);
if (maxUsefulSets == UInt128.Zero)
{
maxUsefulSets = UInt128.One;
}
if (requestedSets == UInt128.Zero || requestedSets > maxUsefulSets)
{
requestedSets = maxUsefulSets;
}
}
if (requestedSets == UInt128.Zero)
{
requestedSets = UInt128.One;
}
UInt128 perSetLimit = DivideRoundUp(totalLimit, requestedSets);
if (perSetLimit == UInt128.Zero)
{
perSetLimit = UInt128.One;
}
UInt128 setsNeeded = DivideRoundUp(totalLimit, perSetLimit);
UInt128 effectiveSets = requestedSets;
if (setsNeeded < effectiveSets)
{
effectiveSets = setsNeeded;
}
bool scanCompleted = false;
if (_useGpuScan)
{
_residueGpuTester!.Scan(exponent, twoP, lastIsSeven, perSetLimit, effectiveSets, totalLimit, ref prePrime, ref scanCompleted);
}
else
{
_residueCpuTester!.Scan(exponent, twoP, lastIsSeven, perSetLimit, effectiveSets, totalLimit, ref prePrime, ref scanCompleted);
}
if (!prePrime)
{
divisorsExhausted = true;
return false;
}
divisorsExhausted = scanCompleted;
return true;
}
return prePrime;
}
if (!_useIncremental)
{
@@ -347,15 +263,12 @@ public sealed class MersenneNumberTester(
if (!prePrime)
{
divisorsExhausted = true;
return false;
}
bool lucasPrime = _useGpuLucas
? _lucasLehmerGpuTester.IsPrime(exponent, runOnGpu: true)
: _lucasLehmerCpuTester.IsPrime(exponent);
divisorsExhausted = true;
return lucasPrime;
return _useGpuLucas
? _lucasLehmerGpuTester.IsPrime(exponent, runOnGpu: true)
: _lucasLehmerCpuTester.IsPrime(exponent);
}
bool isPrime = true;
@@ -383,9 +296,8 @@ public sealed class MersenneNumberTester(
}
}
divisorsExhausted = true;
return isPrime;
}
return isPrime;
}
// Limit of k to scan in the pre-Lucas prescan
public const int PreLucasPreScanK = 5_000_000;