std::condition_variable 练习(多线程任务序列化)

#include <functional>
#include <map>
#include <random>
#include <chrono>
#include <iostream>
#include <format>
#include <cmath>
#include <thread>
#include <future>

struct{
    std::condition_variable cv;
    std::mutex mutex;
    int flag{};
    bool start{};
}g_var;


void thead_sequence_run(int id)
{
    std::cout << "thread[" << id << "] ready\n";
    std::unique_lock lk(g_var.mutex); //由于RAII机制(资源获取即初始化),lk处于lock状态(unique_lock构造方法中调用了mutex.lock)
    g_var.cv.wait(lk, [id]()->bool {return g_var.flag == id; }); //如果被阻塞, cv会自动执行lk.unlock()
    std::cout << "thread[" << id << "] begin\n";
    std::random_device rd;
    std::mt19937 engine(rd());
    std::uniform_int_distribution dis(0, 300);
    std::this_thread::sleep_for(std::chrono::milliseconds(dis(engine)));
    std::cout << "thread[" << id << "] finish\n";
    ++g_var.flag ;
    g_var.cv.notify_all();
}


int main()
{
    using namespace std::chrono_literals;
    int t_cnt = 30;
    std::vector<std::thread> vec_threads;
    for (int i = 0; i < t_cnt; i++) {
        vec_threads.emplace_back(thead_sequence_run, i+1);
    }
    ++g_var.flag;
    g_var.cv.notify_all();
    for (auto& t : vec_threads) {
        t.join();
    }
    std::cout << "g.flag=" << g_var.flag << std::endl;
}