Sprawdź te implementacje :)
int pop(unsigned x) {
x = x - ((x >> 1) & 0x55555555);
x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
x = (x + (x >> 4)) & 0x0F0F0F0F;
x = x + (x >> 8);
x = x + (x >> 16);
return x & 0x0000003F;
}
int pop(unsigned x) {
unsigned n;
n = (x >> 1) & 033333333333;
x = x - n;
n = (n >> 1) & 033333333333;
x = x - n;
x = (x + (x >> 3)) & 030707070707;
return x%63;
}
int pop(unsigned x) {
unsigned n;
n = (x >> 1) & 0x77777777;
x = x - n;
n = (n >> 1) & 0x77777777;
x = x - n;
n = (n >> 1) & 0x77777777;
x = x - n;
x = (x + (x >> 4)) & 0x0F0F0F0F;
x = x*0x01010101;
return x >> 24;
}
int pop(unsigned x) {
int n;
n = 0;
while (x ! = 0) {
n = n + 1;
x= x& (x - 1);
}
return n;
}
int pop(unsigned x) {
unsigned long long y;
y = x * 0x0002000400080010ULL;
y = y & 0x1111111111111111ULL;
y = y * 0x1111111111111111ULL;
y = y >> 60;
return y;
}
Źródło: Hacker's Delight