prime generation with Sieve

#include <iostream>
#include <cmath>
#include <bitset>

using namespace std;

#define MAX 2147483647LL

bitset<(MAX+5)>sieve;

void filter()
{
    int i, j, s = sqrt(MAX);
    sieve[0] = 1;
    sieve[1] = 1;
    for(i = 4; i <= MAX; i += 2)sieve[i] = true;
    for(i = 3; i <= s; i += 2){
        if(!sieve[i]){
            for(j = i*i; j <= MAX; j += (i+i))sieve[j] = true;
        }
    }
}

int main()
{
    filter();
    cout << "Number of primes from 2 to 2^31: " << MAX-sieve.count() << endl;
    return 0;
}