sieve.c

void printf (const char *fmt, ...);
void abort (void);
#define SieveSize 819000
#define N_ITER 10
int sieve (int n) {
  int i, k, prime, count, iter;
  char flags[SieveSize];

  for (iter = 0; iter < n; iter++) {
    count = 0;
    for (i = 0; i < SieveSize; i++) flags[i] = 1;
    for (i = 0; i < SieveSize; i++)
      if (flags[i]) {
        prime = i + i + 3;
        for (k = i + prime; k < SieveSize; k += prime) flags[k] = 0;
        count++;
      }
  }
  return count;
}
int main (void) {
  int n = sieve (N_ITER);

  printf ("%d iterations of sieve for %d: result = %d\n", N_ITER, SieveSize, n);
  if (n != 123814) abort ();
  return 0;
}