sieve.c

/* sieve.c */
/* An old small benchmark from Byte Magazine, circa 1983 and 1984, thus suitable for that vintage of computer. */

#include <stdio.h>
#define TIMES (100000L)
 
static unsigned char f[8192];
 
int main()
{
  int i,s,p,k,c,d=0;
  long int x1;
  
  s = 8192;
  printf("start\n");
  for (x1=0;x1<TIMES;x1++) {
    c = 0;
    for (i=0;i<s;i++) f[i] = 1;
  
    for (i=0;i<s;i++) {
      if (f[i] == 1) {
        p = i+i+3;
        for (k=i;k<s;k+=p) f[k] = 0;
        c++;
      }
    }
    d += c;
  }
  printf("primes found = %d * %ld times = %d\n",c,x1,d);
}