inline void MarkMultiples(BoolArray<>& sieve, const size_t n, const size_t i)
{
size_t cur = i + ((i + 1) * n); // Start at the square of the number.
while (cur < sieve.Size())
{
// Since we're multiplying two odd numbers, the result is always odd, and thus in our sieve.
sieve.ClearBit(cur);
cur += n;
}
}
std::vector<size_t> PrimeFinder::FindPrimes(const size_t until)
{
// Find prime number using the sieve of Eratosthenes
BoolArray<> sieve = GetSieve(until);
size_t expected = GetExpectedPrimeCount(until);
// Check the rest of the range (from sqrt(until) to until) for primes:
std::vector<size_t> primes;
primes.reserve(expected);
primes.push_back(2); // Add 2, the only even prime number, and therefore the only one not in our sieve.
for (size_t i = 0; i < sieve.Size(); i++)
if (sieve[i])
primes.push_back(GetNumberAtIndex(i));
return primes;
}
