基于C++11的threadpool线程池(简洁且可以带任意多的参数)分享！

C++11 加入了线程库，从此告别了标准库不支持并发的历史。然而 c++ 对于多线程的支持还是比较低级，稍微高级一点的用法都需要自己去实现，譬如线程池、信号量等。线程池(thread pool)这个东西，在面试上多次被问到，一般的回答都是：“管理一个任务队列，一个线程队列，然后每次取一个任务分配给一个线程去做，循环往复。” 貌似没有问题吧。但是写起程序来的时候就出问题了。

废话不多说，先上实现，然后再啰嗦。(dont talk, show me ur code !)

代码实现

  #pragma once  #ifndef THREAD_POOL_H  #define THREAD_POOL_H    #include <vector>  #include <queue>  #include <thread>  #include <atomic>  #include <condition_variable>  #include <future>  #include <functional>  #include <stdexcept>    namespace std  {  #define MAX_THREAD_NUM 256    //线程池,可以提交变参函数或拉姆达表达式的匿名函数执行,可以获取执行返回值  //不支持类成员函数, 支持类静态成员函数或全局函数,Opteron()函数等  class threadpool  {    using Task = std::function<void()>;    // 线程池    std::vector<std::thread> pool;    // 任务队列    std::queue<Task> tasks;    // 同步    std::mutex m_lock;    // 条件阻塞    std::condition_variable cv_task;    // 是否关闭提交    std::atomic<bool> stoped;    //空闲线程数量    std::atomic<int> idlThrNum;    public:    inline threadpool(unsigned short size = 4) :stoped{ false }    {      idlThrNum = size < 1 ? 1 : size;      for (size = 0; size < idlThrNum; ++size)      {  //初始化线程数量        pool.emplace_back(          [this]          { // 工作线程函数            while(!this->stoped)            {              std::function<void()> task;              {  // 获取一个待执行的 task                std::unique_lock<std::mutex> lock{ this->m_lock };// unique_lock 相比 lock_guard 的好处是：可以随时 unlock() 和 lock()                this->cv_task.wait(lock,                  [this] {                    return this->stoped.load() || !this->tasks.empty();                  }                ); // wait 直到有 task                if (this->stoped && this->tasks.empty())                  return;                task = std::move(this->tasks.front()); // 取一个 task                this->tasks.pop();              }              idlThrNum--;              task();              idlThrNum++;            }          }        );      }    }    inline ~threadpool()    {      stoped.store(true);      cv_task.notify_all(); // 唤醒所有线程执行      for (std::thread& thread : pool) {        //thread.detach(); // 让线程“自生自灭”        if(thread.joinable())          thread.join(); // 等待任务结束， 前提：线程一定会执行完      }    }    public:    // 提交一个任务    // 调用.get()获取返回值会等待任务执行完,获取返回值    // 有两种方法可以实现调用类成员，    // 一种是使用  bind： .commit(std::bind(&Dog::sayHello, &dog));    // 一种是用 mem_fn： .commit(std::mem_fn(&Dog::sayHello), &dog)    template<class F, class... Args>    auto commit(F&& f, Args&&... args) ->std::future<decltype(f(args...))>    {      if (stoped.load())  // stop == true ??        throw std::runtime_error("commit on ThreadPool is stopped.");        using RetType = decltype(f(args...)); // typename std::result_of<F(Args...)>::type, 函数 f 的返回值类型      auto task = std::make_shared<std::packaged_task<RetType()> >(        std::bind(std::forward<F>(f), std::forward<Args>(args)...)        );  // wtf !      std::future<RetType> future = task->get_future();      {  // 添加任务到队列        std::lock_guard<std::mutex> lock{ m_lock };//对当前块的语句加锁 lock_guard 是 mutex 的 stack 封装类，构造的时候 lock()，析构的时候 unlock()        tasks.emplace(          [task]()          { // push(Task{...})            (*task)();          }        );      }      cv_task.notify_one(); // 唤醒一个线程执行        return future;    }      //空闲线程数量    int idlCount() { return idlThrNum; }    };    }    #endif

代码不多吧,上百行代码就完成了 线程池, 并且, 看看 commit, 哈, 不是固定参数的, 无参数数量限制! 这得益于可变参数模板.

怎么使用?

看下面代码(展开查看)

  #include "threadpool.h"  #include <iostream>    void fun1(int slp)  {    printf(" hello, fun1 ! %dn" ,std::this_thread::get_id());    if (slp>0) {      printf(" ======= fun1 sleep %d ========= %dn",slp, std::this_thread::get_id());      std::this_thread::sleep_for(std::chrono::milliseconds(slp));    }  }    struct gfun {    int operator()(int n) {      printf("%d hello, gfun ! %dn" ,n, std::this_thread::get_id() );      return 42;    }  };    class A {   public:    static int Afun(int n = 0) {  //函数必须是 static 的才能直接使用线程池      std::cout << n << " hello, Afun ! " << std::this_thread::get_id() << std::endl;      return n;    }      static std::string Bfun(int n, std::string str, char c) {      std::cout << n << " hello, Bfun ! "<< str.c_str() <<" " << (int)c <<" " << std::this_thread::get_id() << std::endl;      return str;    }  };    int main()    try {      std::threadpool executor{ 50 };      A a;      std::future<void> ff = executor.commit(fun1,0);      std::future<int> fg = executor.commit(gfun{},0);      std::future<int> gg = executor.commit(a.Afun, 9999); //IDE提示错误,但可以编译运行      std::future<std::string> gh = executor.commit(A::Bfun, 9998,"mult args", 123);      std::future<std::string> fh = executor.commit([]()->std::string { std::cout << "hello, fh ! " << std::this_thread::get_id() << std::endl; return "hello,fh ret !"; });        std::cout << " ======= sleep ========= " << std::this_thread::get_id() << std::endl;      std::this_thread::sleep_for(std::chrono::microseconds(900));        for (int i = 0; i < 50; i++) {        executor.commit(fun1,i*100 );      }      std::cout << " ======= commit all ========= " << std::this_thread::get_id()<< " idlsize="<<executor.idlCount() << std::endl;        std::cout << " ======= sleep ========= " << std::this_thread::get_id() << std::endl;      std::this_thread::sleep_for(std::chrono::seconds(3));        ff.get(); //调用.get()获取返回值会等待线程执行完,获取返回值      std::cout << fg.get() << " " << fh.get().c_str()<< " " << std::this_thread::get_id() << std::endl;        std::cout << " ======= sleep ========= " << std::this_thread::get_id() << std::endl;      std::this_thread::sleep_for(std::chrono::seconds(3));        std::cout << " ======= fun1,55 ========= " << std::this_thread::get_id() << std::endl;      executor.commit(fun1,55).get();  //调用.get()获取返回值会等待线程执行完        std::cout << "end... " << std::this_thread::get_id() << std::endl;          std::threadpool pool(4);      std::vector< std::future<int> > results;        for (int i = 0; i < 8; ++i) {        results.emplace_back(          pool.commit([i] {            std::cout << "hello " << i << std::endl;            std::this_thread::sleep_for(std::chrono::seconds(1));            std::cout << "world " << i << std::endl;            return i*i;          })        );      }      std::cout << " ======= commit all2 ========= " << std::this_thread::get_id() << std::endl;        for (auto && result : results)        std::cout << result.get() << ' ';      std::cout << std::endl;      return 0;    }  catch (std::exception& e) {    std::cout << "some unhappy happened... " << std::this_thread::get_id() << e.what() << std::endl;  }

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