#ifndef thread_pool_h
#define thread_pool_h
#include
#include
#include
#include
#include
#include
#include
#include
#include
class threadpool {
public:
threadpool(size_t);
template
auto enqueue(f&& f, args&&... args)
-> std::future::type>;
~threadpool();
private:
// need to keep track of threads so we can join them
std::vector workers;
// the task queue
std::queue > 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(false) {
for (size_t i = 0; i < threads; i)
workers.emplace_back([this] {
for (;;) {
std::function task;
{
std::unique_lock 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();
}
});
}
// add new work item to the pool
template
auto threadpool::enqueue(f&& f, args&&... args)
-> std::future::type> {
using return_type = typename std::result_of::type;
auto task = std::make_shared >(
std::bind(std::forward(f), std::forward(args)...));
std::future res = task->get_future();
{
std::unique_lock 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() {
{
std::unique_lock lock(queue_mutex);
stop = true;
}
condition.notify_all();
for (std::thread& worker : workers) worker.join();
}
#endif