目录
1. 概述
2. 例程
（1）ThreadPool.h
（2）ThreadPool.cpp
（3）Start.cpp
（4）编译
1. 概述
线程池技术绝不是C++独有的，Java和Python都有比较晚完善的线程池构造接口。
通俗的讲，线程池只是一种管理线程的方式。很多时候，我们为了充分利用CPU和Memory资源，会创建一些独立的线程，执行同步或异步的任务。但有一个不得不考虑的问题是，现成的创建和销毁本身也是消耗系统资源的，尤其是一些需要频繁创建和销毁线程的应用场景下。当然有时候有一些连续的任务也不需要通过线程池技术来完成。
如上所述，为了避免频繁创建和销毁线程带来的系统资源的消耗，我们可以提前创建一定数量的线程，用来等待和处理队列中的事务，无需反复地创建和销毁线程。
2. 例程
（1）ThreadPool.h
#ifndef __THREADPOOL_H__#define __THREADPOOL_H__#include <iostream> #include <vector> #include <queue> #include <thread> #include <mutex> #include <condition_variable> #include <future>#include <functional>#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <stdint.h>class ThreadPool{public: ThreadPool(size_t threads);template<class F, class... 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)(); }); } condition.notify_one(); return res; }~ThreadPool();private: std::vector<std::thread> workers; std::queue<std::function<void()>> tasks; std::mutex queueMutex; std::condition_variable condition; bool stop; };#endif ///< __THREADPOOL_H__（2）ThreadPool.cpp
#include "ThreadPool.h"ThreadPool::ThreadPool(size_t threads) : stop(false){for (size_t i = 0; i < threads; ++i) { workers.emplace_back([this] { while (true) { std::function<void()> task; { std::unique_lock<std::mutex> lock(this->queueMutex); this->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(); } }); } }ThreadPool::~ThreadPool(){ { std::unique_lock<std::mutex> lock(queueMutex); stop = true; } condition.notify_all(); for (std::thread &worker : workers) { worker.join(); } } （3）Start.cpp
#include <iostream> #include <vector> #include <queue> #include <thread> #include <mutex> #include <condition_variable> #include <future>#include <functional>#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <stdint.h>#include "ThreadPool.h"/** sudo g++ -std=c++17 -o ./Start.bin ./*.cpp -lpthread */#define EXTERNAL_FUNC 0 ///< 0: 类内部成员///< 1: 类外部成员#if EXTERNAL_FUNC == 1// 定义一个返回整数的函数 int intFunction(int x){return x * x;} // 定义一个返回字符串的函数 std::string stringFunction(std::string s){return s + " world";}int main(int argc, char* argv[]){ThreadPool pool(4); // 使用enqueue来执行intFunction，传入参数4 auto result1 = pool.enqueue(intFunction, 4); // 使用enqueue来执行stringFunction，传入参数"hello" auto result2 = pool.enqueue(stringFunction, "hello"); // 获取并打印结果 std::cout << "result1: " << result1.get() << std::endl; // 应该打印出16 std::cout << "result2: " << result2.get() << std::endl; // 应该打印出"hello world" return 0; }#else ///< 作为类成员class DemoClass{public: DemoClass(int num_threads = 1){if(num_threads <= 0 ){num_threads = 1;}pool = new ThreadPool(num_threads);}~DemoClass(){delete pool;pool = nullptr;}void printTask(int n){ std::cout << "Processing " << n << std::endl;} void startProcessing(){for (int i = 1; i <= 50; ++i){pool->enqueue(&DemoClass::printTask, this, i);usleep(1); ///< 短暂的等待是有必要的.} }private:ThreadPool* pool = nullptr;}; int main(int argc, char* argv[]){DemoClass myClass(10); myClass.startProcessing(); return 0; }#endif（4）编译
sudo g++ -std=c++17 -o ./Start.bin ./*.cpp -lpthread
