condition_variable

condition_variable_test.cpp

#include <condition_variable>
#include <mutex>
#include <thread>
#include <iostream>
#include <queue>
#include <chrono>
using namespace std;
using namespace std::chrono_literals;
int main()
{
    // lock
    std::queue<int> produced_nums;
    std::mutex m;
    std::condition_variable con_var;

    // variable
    bool done = false;
    bool notified = false;

    std::thread producer([&](){
            for(int i=0; i<5; ++i) {
                std::this_thread::sleep_for(std::chrono::seconds(2));
                std::unique_lock<std::mutex> lock(m);
                std::cout<<"producing "<<i<<endl;
                produced_nums.push(i);

                notified = true;
                // con_var.notify_all();
                con_var.notify_one();
                std::this_thread::sleep_for(std::chrono::seconds(2));
            }

            done = true;
            con_var.notify_all();
        });

    std::thread consumer([&]() {
            std::unique_lock<std::mutex> lock(m);
            while(!done) {
                //con_var.wait(lock, [&]{return notified;});
                if(!notified) con_var.wait(lock);
                while(!produced_nums.empty()) {
                    std::cout<<"consuming " <<produced_nums.front()<<" consumer1"<<endl;
                    produced_nums.pop();
                }
                std::cout<<"thread id: 1 "<<"wake up"<<std::endl; 
                notified = false;
            }
            notified = true;
    });

    std::thread consumer2([&]() {
            std::unique_lock<std::mutex> lock(m);
            while(!done) {
                std::this_thread::sleep_for(std::chrono::seconds(1));
                //con_var.wait(lock, [&]{return notified;});
                if(!notified) con_var.wait(lock);
                while(!produced_nums.empty()) {
                    std::cout<<"consuming " <<produced_nums.front()<<" consumer2"<<endl;
                    produced_nums.pop();
                }
                std::cout<<"thread id: 2 "<<"wake up"<<std::endl; 
                notified = false;
            }
            notified = true;
    });

    producer.join();
    consumer.join();
    consumer2.join();
    /*
    std::this_thread::sleep_for(1s);
    std::cout<<"id1:"<<consumer.get_id()<<endl;
    std::cout<<"id2:"<<consumer2.get_id()<<std::endl;
    std::cout<<"producer:"<<producer.get_id()<<std::endl;
    */
}