How to add a Manager

[Zzzzzya]

No description provided.

[Zzzzzya]

in this demo ,the num of threads in the pool is fixed when the pool is created. Is there a more flexible algorithm or strategy ? How can i add a manager. I mean , in real project ,what should i add to the threadpool? Sorry that my English may be not very good. /(ㄒoㄒ)/~~

[xiays146]

maybe you can fix the following Start func to your own:
`
#ifndef THREAD_POOL_H
#define THREAD_POOL_H

#include
#include
#include
#include
#include
#include <condition_variable>
#include
#include
#include

class ThreadPool
{
public:
ThreadPool(size_t);
template <class F, class... Args>
auto enqueue(F &&f, Args &&...args) -> std::future<typename std::result_of<F(Args...)>::type>;
~ThreadPool();
ThreadPool(const ThreadPool &) = delete;
ThreadPool(ThreadPool &&) = delete;
ThreadPool &operator=(const ThreadPool &) = delete;
ThreadPool &operator=(ThreadPool &&) = delete;
void Stop()
{
if (stop)
return;
{
std::unique_lockstd::mutex lock(queue_mutex);
stop = true;
}
condition.notify_all();
for (std::thread &worker : workers) {
if (worker.joinable())
worker.join();
}
}

void Start(size_t threads)
{
    if (!stop)
        return;
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        stop = false;
    }
    // TODO: clear workers
    for (size_t i = 0; i < threads; ++i) {
        workers.emplace_back([this] {
            for (;;) {
                std::function<void()> task;

                {
                    std::unique_lock<std::mutex> lock(this->queue_mutex);
                    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();
            }
        });
    }
}

private:
// need to keep track of threads so we can join them
std::vectorstd::thread workers;
// the task queue
std::queue<std::function<void()>> tasks;

// synchronization
std::mutex queue_mutex;
std::condition_variable condition;
bool stop;

};

// the constructor just launches some amount of workers
inline ThreadPool::ThreadPool(size_t threads) : stop(true)
{
Start(threads);
}

// add new work item to the pool
template <class F, class... Args>
auto ThreadPool::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(queue_mutex);

    // don't allow enqueueing after stopping the pool
    if (stop)
        throw std::runtime_error("enqueue on stopped ThreadPool");

    tasks.emplace([task]() { (*task)(); });
}
condition.notify_one();
return res;

}

// the destructor joins all threads
inline ThreadPool::~ThreadPool()
{
Stop();
}

#endif
`