private void GetDivisors(bool[] block)
{
// Sieve for all primes < sqrt(size).
var sublimit = (int)Math.Ceiling(Math.Sqrt(limit));
primes.AddPrime(2);
for (var i = 3; i < sublimit; i += 2)
{
if (!block[i])
{
for (var j = i * i; j < limit; j += i)
{
block[j] = true;
}
primes.AddPrime((uint)i);
}
}
for (var i = sublimit | 1; i < limit; i += 2)
{
if (!block[i])
{
primes.AddPrime((uint)i);
}
}
divisors = primes.FirstBucket;
numberOfDivisors = primes.Count;
}
public PrimeCollection(long size, int threads)
{
this.size = Math.Min((long)uint.MaxValue + 1, size);
limit = (int)Math.Ceiling(Math.Sqrt(size));
block = new bool[Math.Max(blockSizeSingleThreaded >> 1, limit)];
primes = new Primes();
if (size <= 13)
{
// Special case for small collections because we handle
// 2 and 3 differently.
foreach (var prime in new uint[] { 2, 3, 5, 7, 11 })
{
if (size > prime)
{
primes.AddPrime(prime);
}
}
}
else
{
GetDivisors(block);
CreateCycle();
GetPrimes(threads);
}
}