How to create a thread pool using boost in C++?

Question

How do I create a thread pool using boost in C++, and how do I assign tasks to the threadpool?

Answer 1

The process is pretty simple. First create an asio::io_service and a thread_group. Fill the thread_group with threads linked to the io_service. Assign tasks to the threads using the boost::bind function.

To stop the threads (usually when you are exiting your program) just stop the io_service and join all threads.

You should only need these headers:

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

here is an example:

/*  * 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(); 

Source: Recipes < Asio