#include <iostream>       // std::cout
#include <atomic>         // std::atomic
#include <thread>         // std::thread
#include <vector>         // std::vector

using namespace std;

atomic<int> atomic_counter (0);
int unsync_counter = 0;

void increase_atomic(int n) {
  for (int i=0; i<n; ++i)
    atomic_counter++;
}

void increase_unsync(int n) {
  for (int i=0; i<n; ++i)
    ++unsync_counter;
}

void waitForThreads(vector<thread> &threads) {
  cout << "wait for all threads..." << endl;
  int joined = 0;
  for (auto & th : threads) {
    th.join();
    joined++;
  }
  threads.clear();
  cout << "join'ed " << joined << " threads" << endl;
}

int main (int argc, char *argv[])
{
  vector<thread> threads;

  cout << endl << "increase atomic counter with 10 threads..." << endl;
  for (int i=1; i<=10; ++i)
    threads.push_back(thread(increase_atomic, 10000000));

  waitForThreads(threads);
  cout << "atomic counter: " << atomic_counter << endl;

  cout << endl << "increase unsynchronized counter with 10 threads..." << endl;
  for (int i=1; i<=10; ++i)
    threads.push_back(thread(increase_unsync, 10000000));
  
  waitForThreads(threads);
  cout << "unsync counter: " << unsync_counter << endl;

  return 0;
}