// Remember to compile with -pthread

#include <pthread.h>
#include <iostream>
#include <unistd.h>

using std::cout;
using std::cerr;
using std::endl;

const int NUM_THREADS = 50; // implicitly static
const int LOOP_NUM = 500;

static int sum_total = 0;
static pthread_mutex_t sum_lock;

void *thread_main(void *arg) {
  for (int i = 0; i < LOOP_NUM; i++) {
    //pthread_mutex_lock(&sum_lock);
    sum_total++;
    //pthread_mutex_unlock(&sum_lock);
  }
  return NULL;
}

int main(int argc, char** argv) {
  pthread_t thds[NUM_THREADS];
  pthread_mutex_init(&sum_lock, NULL);

  for (int i = 0; i < NUM_THREADS; i++) {
    if (pthread_create(&thds[i], NULL, &thread_main, NULL) != 0) {
      cerr << "pthread_create failed" << endl;
    }
  }

  for (int i = 0; i < NUM_THREADS; i++) {
    if (pthread_join(thds[i], NULL) != 0) {
      cerr << "pthread_join failed" << endl;
    }
  }

  cout << "Total: " << sum_total << endl;

  pthread_mutex_destroy(&sum_lock);
  return 0;
}