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111 lines
3.4 KiB
111 lines
3.4 KiB
// Copyright (c) 2012 Jakob Progsch, Václav Zeman
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// This software is provided 'as-is', without any express or implied
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// warranty. In no event will the authors be held liable for any damages
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// arising from the use of this software.
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// Permission is granted to anyone to use this software for any purpose,
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// including commercial applications, and to alter it and redistribute it
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// freely, subject to the following restrictions:
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// 1. The origin of this software must not be misrepresented; you must not
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// claim that you wrote the original software. If you use this software
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// in a product, an acknowledgment in the product documentation would be
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// appreciated but is not required.
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// 2. Altered source versions must be plainly marked as such, and must not be
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// misrepresented as being the original software.
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// 3. This notice may not be removed or altered from any source
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// distribution.
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// this code is from https://github.com/progschj/ThreadPool
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#ifndef BASE_THREAD_POOL_H
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#define BASE_THREAD_POOL_H
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#include <condition_variable>
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#include <functional>
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#include <future>
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#include <memory>
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#include <mutex>
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#include <queue>
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#include <stdexcept>
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#include <thread>
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#include <vector>
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class ThreadPool {
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public:
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explicit ThreadPool(size_t);
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template <class F, class... Args>
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auto enqueue(F&& f, Args&&... args)
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-> std::future<typename std::result_of<F(Args...)>::type>;
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~ThreadPool();
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private:
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// need to keep track of threads so we can join them
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std::vector<std::thread> workers;
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// the task queue
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std::queue<std::function<void()>> tasks;
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// synchronization
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std::mutex queue_mutex;
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std::condition_variable condition;
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bool stop;
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};
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// the constructor just launches some amount of workers
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inline ThreadPool::ThreadPool(size_t threads) : stop(false) {
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for (size_t i = 0; i < threads; ++i)
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workers.emplace_back([this] {
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for (;;) {
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std::function<void()> task;
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{
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std::unique_lock<std::mutex> lock(this->queue_mutex);
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this->condition.wait(lock, [this] {
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return this->stop || !this->tasks.empty();
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});
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if (this->stop && this->tasks.empty()) return;
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task = std::move(this->tasks.front());
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this->tasks.pop();
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}
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task();
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}
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});
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}
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// add new work item to the pool
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template <class F, class... Args>
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auto ThreadPool::enqueue(F&& f, Args&&... args)
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-> std::future<typename std::result_of<F(Args...)>::type> {
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using return_type = typename std::result_of<F(Args...)>::type;
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auto task = std::make_shared<std::packaged_task<return_type()>>(
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std::bind(std::forward<F>(f), std::forward<Args>(args)...));
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std::future<return_type> res = task->get_future();
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{
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std::unique_lock<std::mutex> lock(queue_mutex);
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// don't allow enqueueing after stopping the pool
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if (stop) throw std::runtime_error("enqueue on stopped ThreadPool");
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tasks.emplace([task]() { (*task)(); });
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}
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condition.notify_one();
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return res;
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}
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// the destructor joins all threads
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inline ThreadPool::~ThreadPool() {
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{
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std::unique_lock<std::mutex> lock(queue_mutex);
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stop = true;
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}
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condition.notify_all();
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for (std::thread& worker : workers) worker.join();
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}
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#endif
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