80 lines
2.4 KiB
C#
80 lines
2.4 KiB
C#
using PeterO.Numbers;
|
|
|
|
namespace PerfectNumbers.Core;
|
|
|
|
public static class KRangeFinder
|
|
{
|
|
public static (int? Min, int? Max) FindForPrime(ERational alphaM, EInteger p, int kStart, int kEnd)
|
|
{
|
|
int? min = null;
|
|
int? max = null;
|
|
for (int k = kStart; k <= kEnd; k++)
|
|
{
|
|
ERational aP = AlphaCalculations.ComputeAlphaP(p, k);
|
|
ERational prod = aP.Multiply(alphaM);
|
|
int cmp = prod.CompareTo(RationalNumbers.Two);
|
|
if (cmp == 0)
|
|
{
|
|
if (min == null || k < min)
|
|
{
|
|
min = k;
|
|
}
|
|
if (max == null || k > max)
|
|
{
|
|
max = k;
|
|
}
|
|
}
|
|
if (cmp < 0)
|
|
{
|
|
break;
|
|
}
|
|
}
|
|
return (min, max);
|
|
}
|
|
|
|
public static bool TryFindForPrime(ERational alphaM, EInteger p, out int? min, out int? max, int kStart, int kEnd)
|
|
{
|
|
(min, max) = FindForPrime(alphaM, p, kStart, kEnd);
|
|
return min.HasValue && max.HasValue && min.Value <= max.Value;
|
|
}
|
|
|
|
public static (int? Min, int? Max) Find(ERational alphaM, EInteger pMin, EInteger pMax, int kStart, int kEnd, PrimeCache primes)
|
|
{
|
|
int? min = null;
|
|
int? max = null;
|
|
EInteger[] eulerPrimes = primes.GetEulerPrimes(pMin, pMax);
|
|
object sync = new();
|
|
Parallel.For(
|
|
0,
|
|
eulerPrimes.Length,
|
|
new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount },
|
|
i =>
|
|
{
|
|
(int? localMin, int? localMax) = FindForPrime(alphaM, eulerPrimes[i], kStart, kEnd);
|
|
if (localMin == null)
|
|
{
|
|
return;
|
|
}
|
|
lock (sync)
|
|
{
|
|
if (min == null || localMin < min)
|
|
{
|
|
min = localMin;
|
|
}
|
|
if (max == null || localMax > max)
|
|
{
|
|
max = localMax;
|
|
}
|
|
}
|
|
});
|
|
return (min, max);
|
|
}
|
|
|
|
public static bool TryFind(ERational alphaM, EInteger pMin, EInteger pMax, out int? min, out int? max, int kStart, int kEnd, PrimeCache primes)
|
|
{
|
|
(min, max) = Find(alphaM, pMin, pMax, kStart, kEnd, primes);
|
|
return min.HasValue && max.HasValue && min.Value <= max.Value;
|
|
}
|
|
}
|
|
|