title: boost thread pool
body: <p>I need a threadpool for my application, and I'd like to rely on standard (C++11 or boost) stuff as much as possible. I realize there is an unofficial(!) boost thread pool class, which basically solves what I need, however I'd rather avoid it because it is not in the boost library itself -- why is it still not in the core library after so many years?</p>
  
  <p>In some posts on this page and elsewhere, people suggested using boost::asio to achieve a threadpool like behavior. At first sight, that looked like what I wanted to do, however I found out that all implementations I have seen have no means to join on the currently active tasks, which makes it useless for my application. To perform a join, they send stop signal to all the threads and subsequently join them. However, that completely nullifies the advantage of threadpools in my use case, because that makes new tasks require the creation of a new thread.</p>
  
  <p>What I want to do is:</p>
  
  <pre><code>ThreadPool pool(4);
  for (...)
  {
      for (int i=0;i&lt;something;i++)
          pool.pushTask(...);
      pool.join();
      // do something with the results
  }
  </code></pre>
  
  <p>Can anyone suggest a solution (except for using the existing unofficial thread pool on sourceforge)? Is there anything in C++11 or core boost that can help me here?</p>