#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#define SIZE 10
static int nthreads = 5, delay = 5, sum[SIZE];
pthread_mutex_t sum_lock[SIZE];
int parse_args(int argc,  char *argv[], int *nthreads, int* delay){
  if ((argc != 3) ||
      ((*nthreads = atoi(argv[1])) == 0)  || 
      ((*delay = atoi(argv[2]))  == 0)) {
    fprintf (stderr, "Usage: %s nthreads delay\n", argv[0]);
    return(-1); };
  return(0); 
}
void spin(){
  int j;
  for(j=0; j< delay; j++);
}
void *updater(void *ptr){
  int j;  

  for(j = 0; j < SIZE; j++){
    int i;
    pthread_mutex_lock(&sum_lock[j]);
    spin();  i = sum[j];
    spin();  i++;
    spin();  sum[j] = i; 
    pthread_mutex_unlock(&sum_lock[j]); 
  }
  spin();  pthread_exit(NULL);
}
int main(int argc,  char *argv[]){
  int i;
  if(parse_args(argc, argv, &nthreads, &delay) < 0){
    exit(EXIT_FAILURE);
  } else {
    pthread_t threads[nthreads];    
    for(i = 0; i < SIZE; i++){
      sum[i] = 1;
      pthread_mutex_init(&sum_lock[i], NULL);
    }
    for(i = 0; i < nthreads ; i++)
      pthread_create(&threads[i],NULL,updater,NULL);
    for(i = 0; i < nthreads ; i++)
      pthread_join(threads[i],NULL);
    for(i = 0; i < SIZE; i++)
      fprintf(stderr, "sum[%d] = %d\n", i, sum[i]);
    exit(EXIT_SUCCESS);
  }
}