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Merge pull request #39 from mlemanczyk/codex/fix-evenperfectbitscanner-prime-detection

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Fix GPU residue false positives for Mersenne primes
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Marek Lemańczyk authored and GitHub committed 2025-09-20 09:16:11 +02:00
2 parents 5420523a0a 662cfa8cc7
commit e2eea432c5
3 files changed
+98 -10
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EvenPerfectBitScanner.Tests/ProgramTests.cs
+40
View File
@@ -351,6 +351,46 @@ public class ProgramTests
}
finally
{
useDivisorField.SetValue(null, false);
mersenneField.SetValue(null, null);
primeField.SetValue(null, null);
residueField.SetValue(null, null);
forceCpuProp!.SetValue(null, false);
}
}
[Fact]
public void Residue_mode_with_default_limits_accepts_large_known_primes()
{
var useDivisorField = typeof(Program).GetField("_useDivisor", BindingFlags.NonPublic | BindingFlags.Static)!;
var mersenneField = typeof(Program).GetField("MersenneTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
var primeField = typeof(Program).GetField("PrimeTesters", BindingFlags.NonPublic | BindingFlags.Static)!;
var residueField = typeof(Program).GetField("PResidue", BindingFlags.NonPublic | BindingFlags.Static)!;
var forceCpuProp = typeof(GpuContextPool).GetProperty("ForceCpu");
useDivisorField.SetValue(null, false);
mersenneField.SetValue(null, new ThreadLocal<MersenneNumberTester>(() => new MersenneNumberTester(
useIncremental: true,
useResidue: true,
maxK: 5_000_000UL,
residueDivisorSets: PerfectNumberConstants.ExtraDivisorCycleSearchLimit), trackAllValues: true));
primeField.SetValue(null, new ThreadLocal<PrimeTester>(() => new PrimeTester(), trackAllValues: true));
residueField.SetValue(null, new ThreadLocal<ModResidueTracker>(() => new ModResidueTracker(ResidueModel.Identity, 2UL, true), trackAllValues: true));
forceCpuProp!.SetValue(null, false);
try
{
Program.IsEvenPerfectCandidate(107UL, 0UL, out bool searched, out bool detailed).Should().BeTrue();
searched.Should().BeTrue();
detailed.Should().BeTrue();
Program.IsEvenPerfectCandidate(127UL, 0UL, out searched, out detailed).Should().BeTrue();
searched.Should().BeTrue();
detailed.Should().BeTrue();
}
finally
{
useDivisorField.SetValue(null, false);
mersenneField.SetValue(null, null);
primeField.SetValue(null, null);
residueField.SetValue(null, null);
PerfectNumbers.Core.Tests/MersenneNumberResidueGpuTesterTests.cs
+48
View File
@@ -21,9 +21,57 @@ public class MersenneNumberResidueGpuTesterTests
RunCase(tester, 29UL, 37UL, expectedPrime: false);
RunCase(tester, 31UL, 1_000UL, expectedPrime: true);
RunCase(tester, 89UL, 1_001UL, expectedPrime: true);
RunCase(tester, 107UL, 1_001UL, expectedPrime: true);
RunCase(tester, 127UL, 1_001UL, expectedPrime: true);
}
[Theory]
[InlineData(false)]
[InlineData(true)]
[Trait("Category", "Fast")]
public void Scan_handles_multiple_sets_without_false_positives(bool useGpuOrder)
{
var tester = new MersenneNumberResidueGpuTester(useGpuOrder);
bool isPrime = true;
bool exhausted = false;
UInt128 perSetLimit = 1_666_667UL;
UInt128 setCount = 3UL;
UInt128 overallLimit = 5_000_000UL;
tester.Scan(
127UL,
(UInt128)127UL << 1,
LastDigitIsSeven(127UL),
perSetLimit,
setCount,
overallLimit,
ref isPrime,
ref exhausted);
isPrime.Should().BeTrue();
exhausted.Should().BeTrue();
isPrime = true;
exhausted = false;
perSetLimit = 20_000_000UL;
setCount = 5UL;
overallLimit = 100_000_000UL;
tester.Scan(
107UL,
(UInt128)107UL << 1,
LastDigitIsSeven(107UL),
perSetLimit,
setCount,
overallLimit,
ref isPrime,
ref exhausted);
isPrime.Should().BeTrue();
exhausted.Should().BeTrue();
}
private static void RunCase(MersenneNumberResidueGpuTester tester, ulong exponent, ulong maxK, bool expectedPrime)
{
bool isPrime = true;
PerfectNumbers.Core/Gpu/GpuKernelPool.cs
+10 -10
View File
@@ -195,12 +195,12 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 q = twoP.Mul64(k) + GpuUInt128.One;
// Small-cycles in-kernel early rejection from device table
if (q.High == 0UL && q.Low <= (ulong)(smallCycles.Length - 1))
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
{
uint cyc = smallCycles[(int)q.Low];
if (cyc != 0U && (exponent % cyc) == 0UL)
if (cyc != 0U && (exponent % cyc) != 0UL)
{
orders[index] = exponent;
orders[index] = 0UL;
return;
}
}
@@ -340,12 +340,12 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 k = kStart + (GpuUInt128)idx;
GpuUInt128 q = twoP.Mul64(k) + GpuUInt128.One;
if (q.High == 0UL && q.Low <= (ulong)(smallCycles.Length - 1))
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
{
uint cyc = smallCycles[(int)q.Low];
if (cyc != 0U && (exponent % cyc) == 0UL)
if (cyc != 0U && (exponent % cyc) != 0UL)
{
orders[index] = exponent;
orders[index] = 0UL;
return;
}
}
@@ -468,10 +468,10 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 q = twoP.Mul64(k) + GpuUInt128.One;
// Small-cycles in-kernel early rejection from device table
if (q.High == 0UL && q.Low <= (ulong)(smallCycles.Length - 1))
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
{
uint cyc = smallCycles[(int)q.Low];
if (cyc != 0U && (exponent % (ulong)cyc) == 0UL)
if (cyc != 0U && (exponent % (ulong)cyc) != 0UL)
{
return;
}
@@ -547,10 +547,10 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 k = kStart + (GpuUInt128)idx;
GpuUInt128 q = twoP.Mul64(k) + GpuUInt128.One;
// Small-cycles in-kernel early rejection from device table
if (q.High == 0UL && q.Low <= (ulong)(smallCycles.Length - 1))
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
{
uint cyc = smallCycles[(int)q.Low];
if (cyc != 0U && (exponent % (ulong)cyc) == 0UL)
if (cyc != 0U && (exponent % (ulong)cyc) != 0UL)
{
return;
}