/* =====================================================
   Thread example: find min in array
   ===================================================== */

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


struct timeval start_time, stop_time;


#define MAX  100000000

int    num_threads;
int    start[100];
double x[MAX];
double _min[100];
pthread_t tid[100];




/* --------------------------------------
   Find the min. among my number

   The min is stored in min[s]
   -------------------------------------- */
void *worker(void *arg)
{
   int i, s;
   double my_min;

   s = * (int *) arg;

   my_min = x[s];

   for (i = s+num_threads; i < MAX; i += num_threads)
   {
      if ( x[i] < my_min )
         my_min = x[i];
   }
  
   _min[s] = my_min;
   return(NULL);     /* Thread exits (dies) */
}


int main(int argc, char *argv[])
{
   int i;
   double my_min;
   int elapsed;

   /* -----
      Check command line
      ----- */
   if ( argc != 2 )
   {
      printf("Usage: %s Num_Threads\n\n", argv[0]);
      exit(1);
   }

   /* -------------------------
      Generate random number
      ------------------------- */
   for (i = 0; i < MAX; i++)
      x[i] = random()/(double)1147483648;

   num_threads = atoi(argv[1]);
   printf("Using %d threads...\n\n", num_threads);

   gettimeofday(&start_time, NULL);

   /* ------
      Create threads
      ------ */
   for (i = 0; i < num_threads; i = i + 1)
   {
      start[i] = i;
      if ( pthread_create(&tid[i], NULL, worker, (void *)&start[i]) )
      {
         printf("Cannot create thread\n\n");
         exit(1);
      }
   }

   for (i = 0; i < num_threads; i = i + 1)
      pthread_join(tid[i], NULL);

   my_min = _min[0];
   for (i = 1; i < num_threads; i++)
      if ( _min[i] < my_min )
	 my_min = _min[i];

   gettimeofday(&stop_time, NULL);

   elapsed = (stop_time.tv_sec*1000000 + stop_time.tv_usec) -
   		(start_time.tv_sec*1000000 + start_time.tv_usec);

   printf("min = %e\n\n", my_min);

   printf("Elapsed time = %d microseconds\n\n", elapsed );
}