forPo

#include <sys/time.h>
#include <stdio.h>
#include <pthread.h>

long time_interval(struct timeval tv1, struct timeval tv2) {
  struct timeval dtv;
  dtv.tv_sec = tv2.tv_sec - tv1.tv_sec;
  dtv.tv_usec=tv2.tv_usec-tv1.tv_usec;
  if(dtv.tv_usec<0) {
    dtv.tv_sec--;
    dtv.tv_usec+=1000000;
  }
  return dtv.tv_sec*1000+dtv.tv_usec/1000;
}

volatile int array[100];

void *heavy_loop(void *param) {
  int index = *((int*)param);
  volatile int i;
  for (i = 0; i < 1000000000; i++)
    array[index] = array[index] + 3;
}

int main(int argc, char *argv[]) {
  struct timeval tvs1, tvs2, tvs3, tve1, tve2, tve3;
  struct timezone tz;
  int		first_elem	= 0;
  int		bad_elem	= 1;
  int		good_elem	= 16;
  pthread_t	thread_1;
  pthread_t	thread_2;

  gettimeofday(&tvs1, &tz);
  heavy_loop((void*)&first_elem);
  heavy_loop((void*)&bad_elem);
  gettimeofday(&tve1, &tz);

  gettimeofday(&tvs2, &tz);
  pthread_create(&thread_1, NULL, heavy_loop, (void*)&first_elem);
  pthread_create(&thread_2, NULL, heavy_loop, (void*)&bad_elem);
  pthread_join(thread_1, NULL);
  pthread_join(thread_2, NULL);
  gettimeofday(&tve2, &tz);

  gettimeofday(&tvs3, &tz);
  pthread_create(&thread_1, NULL, heavy_loop, (void*)&first_elem);
  pthread_create(&thread_2, NULL, heavy_loop, (void*)&good_elem);
  pthread_join(thread_1, NULL);
  pthread_join(thread_2, NULL);
  gettimeofday(&tve3, &tz);

  //printf("%d %d %d\n", array[first_elem],array[bad_elem],array[good_elem]);
  printf("Time without using pthread:	%ld ms\n", time_interval(tvs1,tve1));
  printf("Time with wrong using pthread:	%ld ms\n", time_interval(tvs2,tve2));
  printf("Time with right using pthread: 	%ld ms\n", time_interval(tvs3,tve3));

  return 0;
}