C++ 实现线程池的一个例子

模拟场景

执行1000个任务，最大50个线程

定义一个任务类

#include <iostream>
#include <vector>
#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <future>
#include <functional>
#include <memory>
#include <atomic>
#include <iostream>
#include <thread>
#include <sstream>

//执行任务类
class Task {
public:
    explicit Task(int taskId) : taskId(taskId) {}

    int operator()() {
        std::ostringstream oss;
        oss << std::this_thread::get_id() << "-> Task " << taskId << std::endl;
        std::cout << oss.str();
        std::this_thread::sleep_for(std::chrono::milliseconds(100)); // 模拟任务耗时
        return taskId + 5000; // 比如执行 结果 + 5000
    }

private:
    int taskId;
};

实现线程池

// 线程池
class ThreadPool {
public:
    explicit ThreadPool(size_t threadCount) : stop(false) {
        for (size_t i = 0; i < threadCount; ++i) {
            workers.emplace_back([this]() {
                while (true) {
                    std::function<void()> task;
                    {
                        std::unique_lock<std::mutex> lock(queueMutex);
                        condition.wait(lock, [this]() {
                            return this->stop || !this->tasks.empty();
                            });
                        if (this->stop && this->tasks.empty()) {
                            return;
                        }
                        task = std::move(this->tasks.front());
                        this->tasks.pop();
                    }
                    task(); // 执行任务
                    ++tasksCompleted; // 增加已完成任务计数
                    std::ostringstream oss;
                    oss << std::this_thread::get_id() << " -> Progress: " << tasksCompleted << " out of " << totalTasks << " tasks completed." << std::endl;
                    std::cout << oss.str() ;
                }
                });
        }
    }

    template <typename F, typename... Args>
    auto enqueue(F&& f, Args&&... args) -> std::future<typename std::result_of<F(Args...)>::type> {
        using return_type = typename std::result_of<F(Args...)>::type;

        auto task = std::make_shared<std::packaged_task<return_type()>>(
            std::bind(std::forward<F>(f), std::forward<Args>(args)...));

        std::future<return_type> res = task->get_future();
        {
            std::unique_lock<std::mutex> lock(queueMutex);
            if (stop) {
                throw std::runtime_error("enqueue on stopped ThreadPool");
            }
            tasks.emplace([task]() { (*task)(); });
            ++totalTasks;  // 增加总任务计数
        }
        condition.notify_one();
        return res;
    }

    ~ThreadPool() {
        {
            std::unique_lock<std::mutex> lock(queueMutex);
            stop = true;
        }
        condition.notify_all();
        for (std::thread& worker : workers) {
            worker.join();
        }
    }

private:
    std::vector<std::thread> workers;       //执行线程
    std::queue<std::function<void()>> tasks;//执行任务
    std::mutex queueMutex;
    std::condition_variable condition;
    bool stop;  //停止线程池
    std::atomic<size_t> tasksCompleted{ 0 }; //完成数量
    std::atomic<size_t> totalTasks{ 0 };    // 总数量
};

调用线程池

int main() {

    // 最大线程数量
    const size_t maxThreads = 50;
    // 一批任务数量
    const size_t totalTasks = 1000;

    ThreadPool pool(maxThreads);

    // 将任务 添加到线程池中执行
    std::vector<std::future<int>> results;
    for (int i = 0; i < totalTasks; ++i) {
        results.emplace_back(pool.enqueue(Task(i)));
    }

    std::vector<int> taskResults;  // 存储所有任务的结果
    for (auto& result : results) {
        taskResults.push_back(result.get());  // 获取每个任务的结果并存储
    }

    std::cout << "All tasks completed!" << std::endl;
    for (const auto& res : taskResults) {
        std::cout << res << " ";  // 输出所有任务的结果
    }
    std::cout << std::endl;

    return 0;
}