ThreadPool

A thread pool for C++ using std::thread and other C++11/14 standard threading utilities.

Easy to use, with some extra functions for a bit more control.

• auto add(Func&& func, Args&&... args)

  This is how jobs are added to the ThreadPool. Accepts a callable object (func) to be queued, along with arguments (args...). Returns a std::future templated to the return type of Func, to obtain the return value.

  Full signature:

   template<typename Func, typename... Args>
   auto add(Func&& func, Args&&... args) -> std::future<typename std::result_of<Func(Args...)>::type>;

• std::size_t threadCount() const

  Returns what the name implies: the number of threads used.

• std::size_t waitingJobs() const

  Returns the number of jobs currently queued (not currently executing).

• Ids ids() const

  Returns a list of the std::thread::ids assigned to the threads being used by the ThreadPool.

   using Ids = std::vector<std::thread::id>;

• void clear()

  Clears the queue of waiting jobs. Does not affect currently executing jobs.

• void pause(bool state)

  Upon being called: if state is true, prevents threads from grabbing another job upon completion of their current job until pause(false) is called.

  if state is false, allows threads to grab more jobs as they finish. This is the default state.

  Note: calling wait() will not wait if pause(true) was called last (ie: call pause(false) after pause(true) and before wait()).

• void wait()

  Blocks until the number of threads waiting for a job is equal to the number of threads (ie: until all threads have nothing to execute).

• Destructor Note

  The destructor does not wait for queued jobs to be finished. It first clears the queue (call to clear()), tells threads to close, wakes up any waiting threads, and then joins to all of them. If you want to wait until the ThreadPool is done, call wait() before its lifetime ends.