typedef struct { 
  pthread_mutex_t count_lock; 
  pthread_cond_t ok_to_proceed; 
  int count; 
} mylib_barrier_t; 
 
void mylib_init_barrier(mylib_barrier_t *b) { 
  b -> count = 0; 
  pthread_mutex_init(&(b -> count_lock), NULL); 
  pthread_cond_init(&(b -> ok_to_proceed), NULL); 
} 
 
void mylib_barrier (mylib_barrier_t *b, int num_threads) { 
  pthread_mutex_lock(&(b -> count_lock)); 
  b -> count ++; 
  if (b -> count == num_threads) { 
    b -> count = 0; 
    pthread_cond_broadcast(&(b -> ok_to_proceed)); 
  } 
  else 
    while (pthread_cond_wait(&(b -> ok_to_proceed), 
			     &(b -> count_lock)) != 0); 
  pthread_mutex_unlock(&(b -> count_lock)); 
}