The Big Programming Thread - Page 303

REDACTED

#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>

void single2bit(long unsigned int n){
struct timeval start, end;

long dt, seconds, useconds;
unsigned int n2=n/2;
unsigned int mallocsize=(n+1)/16;
char* primos=(char*) calloc( mallocsize,1);

unsigned int i,j;
//printf("%u\n",mallocsize);
unsigned int k=sqrt(n);

gettimeofday(&start, NULL);

for ( i=3;i<k;i+=2)
{
if (!(primos[i/16]&(1<<(i/2)%8))) {

for (j=i*i;j<n;j+=2*i) primos[j/16]|= 1 << ((j/2)%8);

printf("%u\n",i);
}

}
gettimeofday(&end, NULL);

seconds = end.tv_sec - start.tv_sec;
useconds = end.tv_usec - start.tv_usec;

dt = ((seconds) * 1000 + useconds/1000.0) + 0.5;


for (i=3;i<n;i+=2) if (!(primos[i/16]&(1<<(i/2)%8))) printf("%u\n",i);




double flops= n*log(log(n))/dt/1000000;


printf("Single2bits\n\tMFlops: %f\n\tTime: %ld\n",flops,dt);
//free(primos);

}


int main (int argc, char *argv[])
{
long unsigned int n=4294967296;
if (argc>1) n=atoi(argv[1]);
single2bit(n);
}