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Small primes array type changed to uint[] to avoid excessive memory use, especially on GPU

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Marek Lemańczyk committed 2025-09-09 23:58:09 +02:00
1 parent dafdc3d6b6
commit 2be49020a9
6 files changed
+63 -90
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PerfectNumbers.Core/PrimesGenerator.cs
+44 -70
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@@ -2,18 +2,14 @@ namespace PerfectNumbers.Core;
public static class PrimesGenerator
{
private static ulong[]? _primes;
private static ulong[]? _primesPow2;
// private static UInt128[]? _primes128;
// private static UInt128[]? _primesPow2_128;
private static uint[]? _primes;
private static ulong[]? _primesPow2;
public static readonly ulong[] SmallPrimes = BuildSmallPrimesInternal();
public static readonly uint[] SmallPrimes = BuildSmallPrimesInternal();
public static readonly ulong[] SmallPrimesPow2 = BuildSmallPrimesPow2Internal();
// public static readonly UInt128[] SmallPrimes128 = BuildSmallPrimes128Internal();
// public static readonly UInt128[] SmallPrimesPow2_128 = BuildSmallPrimesPow2_128Internal();
private static ulong[] BuildSmallPrimesInternal()
private static uint[] BuildSmallPrimesInternal()
{
if (_primes == null)
{
@@ -33,74 +29,52 @@ public static class PrimesGenerator
return _primesPow2!;
}
// private static UInt128[] BuildSmallPrimes128Internal()
// {
// if (_primes == null)
// {
// BuildSmallPrimes();
// }
// return _primes128!;
// }
// private static UInt128[] BuildSmallPrimesPow2_128Internal()
// {
// if (_primesPow2 == null)
// {
// BuildSmallPrimes();
// }
// return _primesPow2_128!;
// }
private static void BuildSmallPrimes()
{
ulong limit = PerfectNumberConstants.PrimesLimit;
var primes = new ulong[limit];
primes[0] = 2UL;
var primesPow2 = new ulong[limit];
primesPow2[0] = 4UL;
uint limit = PerfectNumberConstants.PrimesLimit;
var primes = new uint[limit];
primes[0] = 2;
var primesPow2 = new ulong[limit];
primesPow2[0] = 4;
int j;
ulong i = 3UL, p, sqrt;
bool isPrime;
int primeIndex = 1;
int j;
uint i = 3, p, sqrt;
bool isPrime;
int primeIndex = 1;
for (; i <= limit; i += 2UL)
{
isPrime = true;
sqrt = (ulong)Math.Sqrt(i);
for (j = 0; j < primeIndex; j++)
{
p = primes[j];
if (p > sqrt)
{
break;
}
for (; i <= limit; i += 2)
{
isPrime = true;
sqrt = (uint)Math.Sqrt(i);
for (j = 0; j < primeIndex; j++)
{
p = primes[j];
if (p > sqrt)
{
break;
}
if (i % p == 0UL)
{
isPrime = false;
break;
}
}
if (i % p == 0UL)
{
isPrime = false;
break;
}
}
if (isPrime)
{
primes[primeIndex] = i;
primesPow2[primeIndex] = i * i;
primeIndex++;
}
}
if (isPrime)
{
primes[primeIndex] = i;
primesPow2[primeIndex] = i * i;
primeIndex++;
}
}
Array.Resize(ref primes, primeIndex);
Array.Resize(ref primesPow2, primeIndex);
Array.Resize(ref primes, primeIndex);
Array.Resize(ref primesPow2, primeIndex);
_primes = primes;
_primesPow2 = primesPow2;
// _primes128 = Array.ConvertAll(_primes, p => (UInt128)p);
// _primesPow2_128 = Array.ConvertAll(_primesPow2, p => (UInt128)p);
_primes = primes;
_primesPow2 = primesPow2;
return;
}
return;
}
}