// badcnt.c
// Ejemplo de ejecución concurrente con threads
// que acceden a una variable compartida.
//
// Extraído de un curso de la profesora Mirela Damian,
// Universidad de Villanova
// http://www.csc.villanova.edu/~mdamian/threads/badcnt.txt
/////////////////////////////////////////////////////////////////////

#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>

#define NITER 1000000

int cnt = 0;

void * Count(void * a)
{
  int i, tmp;
  for(i = 0; i < NITER; i++)
  {
      tmp = cnt;      /* copy the global cnt locally */
      tmp = tmp+1;    /* increment the local copy */
      cnt = tmp;      /* store the local value into the global cnt */
  }
}

int main(int argc, char * argv[])
{
  pthread_t tid1, tid2;

  if(pthread_create(&tid1, NULL, Count, NULL))
  {
    printf("\n ERROR creating thread 1");
    exit(1);
  }

  if(pthread_create(&tid2, NULL, Count, NULL))
  {
    printf("\n ERROR creating thread 2");
    exit(1);
  }

  if(pthread_join(tid1, NULL))        /* wait for the thread 1 to finish */
  {
    printf("\n ERROR joining thread");
    exit(1);
  }

  if(pthread_join(tid2, NULL))        /* wait for the thread 2 to finish */
  {
    printf("\n ERROR joining thread");
    exit(1);
  }

  if (cnt < 2 * NITER)
      printf("\n BOOM! cnt is [%d], should be %d\n", cnt, 2*NITER);
  else
      printf("\n OK! cnt is [%d]\n", cnt);

  pthread_exit(NULL);
}