C++11 Producer + Consumer

multi-threading.cpp

#include <chrono>
#include <iostream>
#include <mutex>
#include <queue>
#include <thread>
#include <vector>

std::mutex mutex;
std::queue<int> candidates;
std::condition_variable condition;

void produce() {
  for (int i = 0;; ++i) {
    // complex manufacture
    std::this_thread::sleep_for(std::chrono::seconds(1));
    {
      std::unique_lock<std::mutex> lock(mutex);
      candidates.push(i);
    }
    condition.notify_one();
  }
}

void consume() {
  while (true) {
    int value;
    {
      std::unique_lock<std::mutex> lock(mutex);
      condition.wait(lock, [] { return !candidates.empty(); });
      value = candidates.front();
      candidates.pop();
    }

    // complex calculation
    std::this_thread::sleep_for(std::chrono::seconds(4));
    auto result = value * value;
    std::cout << "Power of " << value << " is " << result << std::endl;
  }
}

int main() {
  std::thread producer(produce);
  std::vector<std::thread> consumers;
  for (int i = 0; i < 4; ++i) {
    consumers.emplace_back(consume);
  }

  producer.join();
  for (auto &consumer: consumers) {
    consumer.join();
  }
  return 0;
}