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Use GpuUInt128 in by-divisor GPU scan

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Marek Lemańczyk committed 2025-10-13 01:35:40 +02:00
1 parent cd47b122a5
commit ea29035c55
2 files changed
+51 -48
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PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs
+37 -30
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@@ -363,27 +363,24 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
return false;
}
UInt128 step128 = (UInt128)prime << 1;
if (step128 == UInt128.Zero)
GpuUInt128 step128 = new GpuUInt128(prime);
step128.ShiftLeft(1);
if (step128.IsZero)
{
processedAll = true;
return false;
}
if (step128 > ulong.MaxValue)
{
return CheckDivisorsCpu(prime, allowedMax, out lastProcessed, out processedAll, out processedCount, timeLimit);
}
UInt128 limit = allowedMax;
UInt128 divisor128 = step128 + UInt128.One;
if (divisor128 > limit)
GpuUInt128 limit128 = new GpuUInt128(allowedMax);
GpuUInt128 divisor128 = step128;
divisor128.Add(1UL);
if (divisor128.CompareTo(limit128) > 0)
{
processedAll = true;
return false;
}
ulong step = (ulong)step128;
ulong step = step128.Low;
ulong limit64 = allowedMax;
int batchCapacity = Math.Max(1, _batchSize);
@@ -412,20 +409,27 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
byte step7 = (byte)(step % 7UL);
byte step11 = (byte)(step % 11UL);
byte remainder10 = (byte)((ulong)divisor128 % 10UL);
byte remainder8 = (byte)((ulong)divisor128 % 8UL);
byte remainder5 = (byte)((ulong)divisor128 % 5UL);
byte remainder3 = (byte)((ulong)divisor128 % 3UL);
byte remainder7 = (byte)((ulong)divisor128 % 7UL);
byte remainder11 = (byte)((ulong)divisor128 % 11UL);
ulong startDivisor64 = divisor128.Low;
byte remainder10 = (byte)(startDivisor64 % 10UL);
byte remainder8 = (byte)(startDivisor64 % 8UL);
byte remainder5 = (byte)(startDivisor64 % 5UL);
byte remainder3 = (byte)(startDivisor64 % 3UL);
byte remainder7 = (byte)(startDivisor64 % 7UL);
byte remainder11 = (byte)(startDivisor64 % 11UL);
bool lastIsSeven = (prime & 3UL) == 3UL;
try
{
while (divisor128 <= limit)
while (divisor128.CompareTo(limit128) <= 0)
{
int chunkCount = ComputeChunkCount(divisor128, limit, step128, batchCapacity);
if (divisor128.High != 0UL)
{
break;
}
ulong currentDivisor = divisor128.Low;
int chunkCount = ComputeChunkCount(currentDivisor, limit64, step, batchCapacity);
if (chunkCount <= 0)
{
break;
@@ -435,7 +439,7 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
Span<byte> maskSpan = maskBuffer.AsSpan(0, chunkCount);
candidateEvaluator.EvaluateCandidates(
(ulong)divisor128,
currentDivisor,
step,
limit64,
remainder10,
@@ -508,7 +512,10 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
}
}
divisor128 += step128 * (UInt128)chunkCount;
GpuUInt128 increment = step128;
increment.Mul((ulong)chunkCount);
divisor128.Add(increment);
remainder10 = AdvanceRemainder(remainder10, step10, 10, chunkCount);
remainder8 = AdvanceRemainder(remainder8, step8, 8, chunkCount);
remainder5 = AdvanceRemainder(remainder5, step5, 5, chunkCount);
@@ -524,26 +531,26 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
candidateEvaluator.Dispose();
}
processedAll = divisor128 > limit;
processedAll = divisor128.CompareTo(limit128) > 0;
return false;
}
private static int ComputeChunkCount(UInt128 currentDivisor, UInt128 limit, UInt128 step, int maxCount)
private static int ComputeChunkCount(ulong currentDivisor, ulong limit, ulong step, int maxCount)
{
if (maxCount <= 0 || step == UInt128.Zero || currentDivisor > limit)
if (maxCount <= 0 || step == 0UL || currentDivisor > limit)
{
return 0;
}
UInt128 distance = limit - currentDivisor;
UInt128 stepsAvailable = distance / step;
UInt128 total = stepsAvailable + UInt128.One;
if (total > (UInt128)maxCount)
ulong distance = limit - currentDivisor;
ulong stepsAvailable = step == 0UL ? 0UL : distance / step;
ulong total = stepsAvailable + 1UL;
if (total > (ulong)maxCount)
{
total = (UInt128)maxCount;
total = (ulong)maxCount;
}
if (total > (UInt128)int.MaxValue)
if (total > (ulong)int.MaxValue)
{
return int.MaxValue;
}