ThreadPool.h
#pragma once
#ifndef THREAD_POOL_H
#define THREAD_POOL_H
#include <atomic>
#include <future>
#include <queue>
#include <vector>
// #include <condition_variable>
// #include <thread>
// #include <functional>
#include <stdexcept>
namespace std {
// 线程池最大容量,应尽量设小一点
#define THREADPOOL_MAX_NUM 16
// 线程池是否可以自动增长(如果需要,且不超过THREADPOOL_MAX_NUM)
// #define THREADPOOL_AUTO_GROW
// 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
// 不直接支持类成员函数, 支持类静态成员函数或全局函数,Opteron()函数等
class threadpool {
unsigned short init_size_; // 初始化线程数量
using Task = function<void()>; // 定义类型
vector<thread> pool_; // 线程池
queue<Task> tasks_; // 任务队列
mutex lock_; // 任务队列同步锁
#ifdef THREADPOOL_AUTO_GROW
mutex lock_grow_; // 线程池增长同步锁
#endif // !THREADPOOL_AUTO_GROW
condition_variable task_cv_; // 条件阻塞
atomic<bool> run_{true}; // 线程池是否执行
atomic<int> idle_tid_num_{0}; // 空闲线程数量
public:
inline threadpool(unsigned short size = 4) {
init_size_ = size;
addThread(size);
}
inline ~threadpool() {
run_ = false;
task_cv_.notify_all(); // 唤醒所有线程执行
for (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), this)
template <class F, class... Args>
auto commit(F &&f, Args &&...args) -> future<decltype(f(args...))> {
if (!run_) // stoped ??
throw 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 = make_shared<packaged_task<RetType()>>(bind(
forward<F>(f), forward<Args>(args)...)); // 把函数入口及参数,打包(绑定)
future<RetType> future = task->get_future();
{ // 添加任务到队列
lock_guard<mutex> lock{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{...}) 放到队列后面
(*task)();
});
}
#ifdef THREADPOOL_AUTO_GROW
if (idle_tid_num_ < 1 && pool_.size() < THREADPOOL_MAX_NUM)
addThread(1);
#endif // !THREADPOOL_AUTO_GROW
task_cv_.notify_one(); // 唤醒一个线程执行
return future;
}
// 提交一个无参任务, 且无返回值
template <class F> void commit2(F &&task) {
if (!run_)
return;
{
lock_guard<mutex> lock{lock_};
tasks_.emplace(std::forward<F>(task));
}
#ifdef THREADPOOL_AUTO_GROW
if (idle_tid_num_ < 1 && pool_.size() < THREADPOOL_MAX_NUM)
addThread(1);
#endif // !THREADPOOL_AUTO_GROW
task_cv_.notify_one();
}
// 空闲线程数量
int idlCount() { return idle_tid_num_; }
// 线程数量
int thrCount() { return pool_.size(); }
#ifndef THREADPOOL_AUTO_GROW
private:
#endif // !THREADPOOL_AUTO_GROW
// 添加指定数量的线程
void addThread(unsigned short size) {
#ifdef THREADPOOL_AUTO_GROW
if (!run_) // stoped ??
throw runtime_error("Grow on ThreadPool is stopped.");
unique_lock<mutex> lock_grow{lock_grow_}; // 自动增长锁
#endif // !THREADPOOL_AUTO_GROW
for (; pool_.size() < THREADPOOL_MAX_NUM && size > 0; --size) {
// 增加线程数量,但不超过 预定义数量 THREADPOOL_MAX_NUM
pool_.emplace_back([this] { // 工作线程函数
while (true) // 防止 run_==false 时立即结束, 此时任务队列可能不为空
{
Task task; // 获取一个待执行的 task
{
// unique_lock 相比 lock_guard 的好处是:可以随时 unlock() 和 lock()
unique_lock<mutex> lock{lock_};
task_cv_.wait(lock, [this] { // wait 直到有 task, 或需要停止
return !run_ || !tasks_.empty();
});
if (!run_ && tasks_.empty())
return;
idle_tid_num_--;
task = move(tasks_.front()); // 按先进先出从队列取一个 task
tasks_.pop();
}
task(); // 执行任务
#ifdef THREADPOOL_AUTO_GROW
if (idle_tid_num_ > 0 && pool_.size() > init_size_)
return;
// 支持自动释放空闲线程,避免峰值过后大量空闲线程
#endif // !THREADPOOL_AUTO_GROW
{
unique_lock<mutex> lock{lock_};
idle_tid_num_++;
}
}
});
{
unique_lock<mutex> lock{lock_};
idle_tid_num_++;
}
}
}
};
} // namespace std
#endif
main.cpp
#include "threadpool.h"
#include <iostream>
#include <windows.h>
void fun1(int slp) {
printf(" hello, fun1 ! %d\n", std::this_thread::get_id());
if (slp > 0) {
printf(" ======= fun1 sleep %d ========= tid:%d\n", slp,
std::this_thread::get_id());
std::this_thread::sleep_for(std::chrono::milliseconds(slp));
// Sleep(slp );
}
}
struct gfun {
int operator()(int n) {
printf("%d hello, gfun ! tid:%d\n", n, std::this_thread::get_id());
return 42;
}
};
class A { // 函数必须是 static 的才能使用线程池
public:
static int Afun(int n = 0) {
std::cout << n << " hello, Afun ! tid:" << 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
<< " tid:" << 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! tid:" << std::this_thread::get_id() << std::endl;
return "hello, fh ret!";
});
std::cout << " ======= sleep ========= tid:" << 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 ========= tid:"
<< std::this_thread::get_id() << " idlsize=" << executor.idlCount()
<< std::endl;
std::cout << " ======= sleep ========= tid:" << 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()
<< " tid:" << std::this_thread::get_id() << std::endl;
std::cout << " ======= sleep ========= tid:" << std::this_thread::get_id()
<< std::endl;
std::this_thread::sleep_for(std::chrono::seconds(3));
std::cout << " ======= fun1,55 ========= tid:" << 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... tid:" << 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 ========= tid:"
<< 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... tid:" << std::this_thread::get_id()
<< e.what() << std::endl;
}