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
+16 -9
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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++) for (k2 = 1UL; k2 <= limit; k2++)
{ {
kMul2 = (UInt128)k2 << 1; 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) if (p < 64UL && d == ((UInt128)1 << (int)p) - UInt128.One)
{ {
continue; continue;
PerfectNumbers.Core/Gpu/MersenneNumberResidueGpuTester.cs
+14 -8
View File
@@ -44,20 +44,25 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
var orderBuffer = accelerator.Allocate1D<ulong>(batchSize); var orderBuffer = accelerator.Allocate1D<ulong>(batchSize);
ulong[] orderArray = ArrayPool<ulong>.Shared.Rent(batchSize); ulong[] orderArray = ArrayPool<ulong>.Shared.Rent(batchSize);
UInt128 batchSize128 = (UInt128)batchSize; UInt128 batchSize128 = (UInt128)batchSize;
UInt128 limitInclusive = overallLimit + UInt128.One; UInt128 limitInclusive = overallLimit == UInt128.MaxValue
? overallLimit
: checked(overallLimit + UInt128.One);
Span<ulong> orders = orderArray.AsSpan(0, batchSize); Span<ulong> orders = orderArray.AsSpan(0, batchSize);
try try
{ {
for (UInt128 setIndex = UInt128.Zero; setIndex < setCount && Volatile.Read(ref isPrime); setIndex++) for (ulong setIndex = 0; setIndex < setCount && Volatile.Read(ref isPrime); setIndex++)
{ {
UInt128 setOffset = perSetLimit * setIndex; UInt128 setOffset = checked(perSetLimit * (UInt128)setIndex);
UInt128 setStart = setOffset + UInt128.One; UInt128 setStart = checked(setOffset + UInt128.One);
if (setStart >= limitInclusive) if (setStart >= limitInclusive)
{ {
break; break;
} }
UInt128 setLimitExclusive = setOffset + perSetLimit + UInt128.One; UInt128 setLimitExclusive = checked(setOffset + perSetLimit);
setLimitExclusive = setLimitExclusive >= limitInclusive
? limitInclusive
: checked(setLimitExclusive + UInt128.One);
if (setLimitExclusive > limitInclusive) if (setLimitExclusive > limitInclusive)
{ {
setLimitExclusive = limitInclusive; setLimitExclusive = limitInclusive;
@@ -66,7 +71,7 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
UInt128 kStart = setStart; UInt128 kStart = setStart;
while (kStart < setLimitExclusive && Volatile.Read(ref isPrime)) while (kStart < setLimitExclusive && Volatile.Read(ref isPrime))
{ {
UInt128 remaining = setLimitExclusive - kStart; UInt128 remaining = checked(setLimitExclusive - kStart);
int currentSize = remaining > batchSize128 ? batchSize : (int)remaining; int currentSize = remaining > batchSize128 ? batchSize : (int)remaining;
if (currentSize <= 0) if (currentSize <= 0)
{ {
@@ -74,7 +79,8 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
} }
orders = orderArray.AsSpan(0, currentSize); orders = orderArray.AsSpan(0, currentSize);
UInt128 q = twoP * kStart + UInt128.One; 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); 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); var ra = new ResidueAutomatonArgs(q0m10, step10, q0m8, step8, q0m3, step3, q0m5, step5);
@@ -97,7 +103,7 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
} }
} }
kStart += batchSize128; kStart = checked(kStart + batchSize128);
} }
} }
} }