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¿Cómo crear un grupo de subprocesos usando boost en C++?

Question

¿Cómo creo un grupo de subprocesos usando boost en C ++ y cómo asigno tareas al threadpool?

Answer 1

El proceso es bastante simple. Primero crea un asio :: io_service y un thread_group. Rellene thread_group con hilos vinculados al io_service. Asigna tareas a los hilos utilizando la función boost::bind .

Para detener los hilos (generalmente cuando sale de su programa) solo detenga el io_service y únase a todos los hilos.

Solo deberías necesitar estos encabezados:

#include <boost/asio/io_service.hpp>
#include <boost/bind.hpp>
#include <boost/thread/thread.hpp>

Aquí hay un ejemplo:

/*
* Create an asio::io_service and a thread_group (through pool in essence)
*/
boost::asio::io_service ioService;
boost::thread_group threadpool;
/*
* This will start the ioService processing loop. All tasks
* assigned with ioService.post() will start executing.
*/
boost::asio::io_service::work work(ioService);
/*
* This will add 2 threads to the thread pool. (You could just put it in a for loop)
*/
threadpool.create_thread(
boost::bind(&boost::asio::io_service::run, &ioService)
);
threadpool.create_thread(
boost::bind(&boost::asio::io_service::run, &ioService)
);
/*
* This will assign tasks to the thread pool.
* More about boost::bind: "http://www.boost.org/doc/libs/1_54_0/libs/bind/bind.html#with_functions"
*/
ioService.post(boost::bind(myTask, "Hello World!"));
ioService.post(boost::bind(clearCache, "./cache"));
ioService.post(boost::bind(getSocialUpdates, "twitter,gmail,facebook,tumblr,reddit"));
/*
* This will stop the ioService processing loop. Any tasks
* you add behind this point will not execute.
*/
ioService.stop();
/*
* Will wait till all the threads in the thread pool are finished with
* their assigned tasks and ''join'' them. Just assume the threads inside
* the threadpool will be destroyed by this method.
*/
threadpool.join_all();

Fuente: Recetas <Asio

Answer 2

Sé que te gusta el código.

Mi version

namespace bamthread
{
typedef std::unique_ptr<boost::asio::io_service::work> asio_worker;
struct ThreadPool {
ThreadPool(size_t threads) :service(), working(new asio_worker::element_type(service)) {
while(threads--)
{
auto worker = boost::bind(&boost::asio::io_service::run, &(this->service));
g.add_thread(new boost::thread(worker));
}
}
template<class F>
void enqueue(F f){
service.post(f);
}
~ThreadPool() {
working.reset(); //allow run() to exit
g.join_all();
service.stop();
}
private:
boost::asio::io_service service; //< the io_service we are wrapping
asio_worker working;
boost::thread_group g; //< need to keep track of threads so we can join them
};
}

Pedazo de código para usarlo:

{
bamthread::ThreadPool tp(n_threads);
BOOST_FOREACH(int y, boost::irange(starty, endy, step)){
int im_x = 0;
BOOST_FOREACH(int x, boost::irange(startx, endx, step)){
tp.enqueue (boost::bind(&camera_view_depth::threaded_intersection, this,
intersections,
intersected,
im_x,
im_y,
_faces, x, y));
++im_x;
}
++im_y;
}
}