Exemplo n.º 1
0
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;
	} 
}
Exemplo n.º 2
0
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;
}