mlemanczyk/even-perfect-numbers-scanner
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Calculation switched to typical O(N)

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mlemanczyk committed 2025-10-12 18:23:06 +02:00
1 parent 7562f14b1c
commit d555e157f6
1 file changed
+44 -44
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PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs
+44 -44
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@@ -1812,56 +1812,56 @@ internal static partial class PrimeOrderGpuHeuristics
{
ulong exponent = exponents[index];
ulong modulus = divisor.Modulus;
ulong nPrime = divisor.NPrime;
ulong result = divisor.MontgomeryOne;
ulong baseValue = divisor.MontgomeryTwo;
ulong remainingExponent = exponent;
// ulong nPrime = divisor.NPrime;
// ulong result = divisor.MontgomeryOne;
// ulong baseValue = divisor.MontgomeryTwo;
// ulong remainingExponent = exponent;
if (remainingExponent == 0UL)
{
remainders[index] = result.MontgomeryMultiply(1UL, modulus, nPrime);
return;
}
// if (remainingExponent == 0UL)
// {
// remainders[index] = result.MontgomeryMultiply(1UL, modulus, nPrime);
// return;
// }
while (remainingExponent != 0UL)
{
if ((remainingExponent & 1UL) != 0UL)
{
result = result.MontgomeryMultiply(baseValue, modulus, nPrime);
}
// while (remainingExponent != 0UL)
// {
// if ((remainingExponent & 1UL) != 0UL)
// {
// result = result.MontgomeryMultiply(baseValue, modulus, nPrime);
// }
remainingExponent >>= 1;
if (remainingExponent == 0UL)
{
break;
}
// remainingExponent >>= 1;
// if (remainingExponent == 0UL)
// {
// break;
// }
// Reusing baseValue to hold base^2 so we avoid allocating another register for the squared term.
baseValue = baseValue.MontgomeryMultiply(baseValue, modulus, nPrime);
}
// // Reusing baseValue to hold base^2 so we avoid allocating another register for the squared term.
// baseValue = baseValue.MontgomeryMultiply(baseValue, modulus, nPrime);
// }
remainders[index] = result.MontgomeryMultiply(1UL, modulus, nPrime);
// remainders[index] = result.MontgomeryMultiply(1UL, modulus, nPrime);
// Plain modular exponentiation without Montgomery reduction kept for reference.
// ulong plainResult = 1UL % modulus;
// ulong plainBase = 2UL % modulus;
// ulong plainExponent = exponent;
// while (plainExponent != 0UL)
// {
// if ((plainExponent & 1UL) != 0UL)
// {
// plainResult = (plainResult * plainBase) % modulus;
// }
//
// plainExponent >>= 1;
// if (plainExponent == 0UL)
// {
// break;
// }
//
// plainBase = (plainBase * plainBase) % modulus;
// }
// remainders[index] = plainResult;
// Plain modular exponentiation without Montgomery reduction kept for reference.
ulong plainResult = 1UL;// % modulus;
ulong plainBase = 2UL;// % modulus;
while (exponent != 0UL)
{
if ((exponent & 1UL) != 0UL)
{
plainResult = (plainResult * plainBase) % modulus;
}
exponent >>= 1;
if (exponent == 0UL)
{
break;
}
plainBase = (plainBase * plainBase) % modulus;
}
remainders[index] = plainResult;
}
private static Action<AcceleratorStream, Index1D, ArrayView1D<GpuUInt128, Stride1D.Dense>, GpuUInt128, ArrayView1D<GpuUInt128, Stride1D.Dense>> GetPow2ModWideKernel(Accelerator accelerator)