mlemanczyk/even-perfect-numbers-scanner
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Guard GPU residue and divisor scans against overflow

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Marek Lemańczyk committed 2025-09-20 03:21:49 +02:00
1 parent ff2c516a0e
commit 9f2cf12ce1
2 files changed
+66 -59
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PerfectNumbers.Core/Gpu/MersenneNumberDivisorGpuTester.cs
+2 -1
View File
@@ -95,7 +95,8 @@ public sealed class MersenneNumberDivisorGpuTester
for (k2 = 1UL; k2 <= limit; k2++)
{
kMul2 = (UInt128)k2 << 1;
d = kMul2 * p + UInt128.One;
UInt128 candidate = checked(kMul2 * p);
d = checked(candidate + UInt128.One);
if (p < 64UL && d == ((UInt128)1 << (int)p) - UInt128.One)
{
continue;
PerfectNumbers.Core/Gpu/MersenneNumberResidueGpuTester.cs
+64 -58
View File
@@ -41,72 +41,78 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
ulong step5 = ((exponent % 5UL) << 1) % 5UL;
GpuUInt128 twoPGpu = (GpuUInt128)twoP;
var orderBuffer = accelerator.Allocate1D<ulong>(batchSize);
ulong[] orderArray = ArrayPool<ulong>.Shared.Rent(batchSize);
UInt128 batchSize128 = (UInt128)batchSize;
UInt128 limitInclusive = overallLimit + UInt128.One;
Span<ulong> orders = orderArray.AsSpan(0, batchSize);
try
{
for (UInt128 setIndex = UInt128.Zero; setIndex < setCount && Volatile.Read(ref isPrime); setIndex++)
var orderBuffer = accelerator.Allocate1D<ulong>(batchSize);
ulong[] orderArray = ArrayPool<ulong>.Shared.Rent(batchSize);
UInt128 batchSize128 = (UInt128)batchSize;
UInt128 limitInclusive = overallLimit == UInt128.MaxValue
? overallLimit
: checked(overallLimit + UInt128.One);
Span<ulong> orders = orderArray.AsSpan(0, batchSize);
try
{
UInt128 setOffset = perSetLimit * setIndex;
UInt128 setStart = setOffset + UInt128.One;
if (setStart >= limitInclusive)
{
break;
}
for (ulong setIndex = 0; setIndex < setCount && Volatile.Read(ref isPrime); setIndex++)
{
UInt128 setOffset = checked(perSetLimit * (UInt128)setIndex);
UInt128 setStart = checked(setOffset + UInt128.One);
if (setStart >= limitInclusive)
{
break;
}
UInt128 setLimitExclusive = setOffset + perSetLimit + UInt128.One;
if (setLimitExclusive > limitInclusive)
{
setLimitExclusive = limitInclusive;
}
UInt128 setLimitExclusive = checked(setOffset + perSetLimit);
setLimitExclusive = setLimitExclusive >= limitInclusive
? limitInclusive
: checked(setLimitExclusive + UInt128.One);
if (setLimitExclusive > limitInclusive)
{
setLimitExclusive = limitInclusive;
}
UInt128 kStart = setStart;
while (kStart < setLimitExclusive && Volatile.Read(ref isPrime))
{
UInt128 remaining = setLimitExclusive - kStart;
int currentSize = remaining > batchSize128 ? batchSize : (int)remaining;
if (currentSize <= 0)
{
break;
}
orders = orderArray.AsSpan(0, currentSize);
UInt128 kStart = setStart;
while (kStart < setLimitExclusive && Volatile.Read(ref isPrime))
{
UInt128 remaining = checked(setLimitExclusive - kStart);
int currentSize = remaining > batchSize128 ? batchSize : (int)remaining;
if (currentSize <= 0)
{
break;
}
orders = orderArray.AsSpan(0, currentSize);
UInt128 q = twoP * kStart + UInt128.One;
q.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
var ra = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
UInt128 q = checked(twoP * kStart);
q = checked(q + UInt128.One);
q.Mod10_8_5_3(out ulong q0m10, out ulong q0m8, out ulong q0m5, out ulong q0m3);
var ra = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
kernel(currentSize, exponent, twoPGpu, (GpuUInt128)kStart, last, 0UL,
ra, orderBuffer.View, smallCyclesView, primeViews.LastOne, primeViews.LastSeven, primeViews.LastOnePow2, primeViews.LastSevenPow2);
kernel(currentSize, exponent, twoPGpu, (GpuUInt128)kStart, last, 0UL,
ra, orderBuffer.View, smallCyclesView, primeViews.LastOne, primeViews.LastSeven, primeViews.LastOnePow2, primeViews.LastSevenPow2);
accelerator.Synchronize();
orderBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(orders), currentSize);
if (!Volatile.Read(ref isPrime))
{
break;
}
accelerator.Synchronize();
orderBuffer.View.CopyToCPU(ref MemoryMarshal.GetReference(orders), currentSize);
if (!Volatile.Read(ref isPrime))
{
break;
}
for (int i = 0; i < currentSize; i++)
{
if (orders[i] != 0UL)
{
Volatile.Write(ref isPrime, false);
break;
}
}
for (int i = 0; i < currentSize; i++)
{
if (orders[i] != 0UL)
{
Volatile.Write(ref isPrime, false);
break;
}
}
kStart += batchSize128;
}
}
}
finally
{
ArrayPool<ulong>.Shared.Return(orderArray);
orderBuffer.Dispose();
gpuLease.Dispose();
}
kStart = checked(kStart + batchSize128);
}
}
}
finally
{
ArrayPool<ulong>.Shared.Return(orderArray);
orderBuffer.Dispose();
gpuLease.Dispose();
}
divisorsExhausted = true;
}