c_pthreads.c

void iter_threads(int start, int end, void (*func)(int n))
{
  int n = start;
  pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

  void *thread_body(void *ptr)
  {
    double start = now();
    for (;;) {
      pthread_mutex_lock( &mutex );
      int i = (n)++;
      pthread_mutex_unlock( &mutex );
      if (i >= end)
        break;
      func(i);
    }
    fprintf(stderr, "(ok %0.3fs)", now()-start);
    return NULL;
  }

  pthread_t thread_id[NTHREADS];
  for (int i=0; i<NTHREADS; i++)
    pthread_create(&thread_id[i], NULL, thread_body, NULL);
  for (int i=0; i<NTHREADS; i++)
    pthread_join(thread_id[i], NULL);
  fprintf(stderr, "\n");
}