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Add Montgomery multiplication benchmark and optimize implementation

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Marek Lemańczyk committed 2025-09-22 14:04:50 +02:00
1 parent e7668874a6
commit 66d79f7166
2 files changed
+139 -6
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PerfectNumbers.Core/Gpu/MersenneNumberDivisorByDivisorGpuTester.cs
+2 -6
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@@ -377,14 +377,10 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester
private static ulong MontgomeryMultiply(ulong a, ulong b, ulong modulus, ulong nPrime)
{
ulong tLow = unchecked(a * b);
ulong tHigh = MultiplyHigh(a, b);
ulong m = unchecked(tLow * nPrime);
ulong mnLow = unchecked(m * modulus);
ulong mnHigh = MultiplyHigh(m, modulus);
ulong sumLow = unchecked(tLow + mnLow);
ulong sumLow = unchecked(tLow + m * modulus);
ulong carry = sumLow < tLow ? 1UL : 0UL;
ulong sumHigh = unchecked(tHigh + mnHigh + carry);
ulong sumHigh = unchecked(MultiplyHigh(a, b) + MultiplyHigh(m, modulus) + carry);
ulong result = sumHigh;
if (result >= modulus)