#include <stdio.h>
#include <time.h>

int main() {
  struct timespec t0, t1;
  long int i = 0;
  register long int x = 0;

  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t0);
  for (; i < 1000; ++i)
    printf("%ld ", i + 1);
  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t1);
  printf("\n%ldns took usual var", (t1.tv_sec - t0.tv_sec) * (long)1e9 + (t1.tv_nsec - t0.tv_nsec));
  printf("\n\n");

  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t0);
  for (; x < 1000; ++x)
    printf("%ld ", x + 1);
  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &t1);

  printf("\n%ldns took register var", (t1.tv_sec - t0.tv_sec) * (long)1e9 + (t1.tv_nsec - t0.tv_nsec));
}