Hello, v13: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=boost-threadpool.v13.tar.gz&directory=Concurrent%20Programming& after the discussion yesterday I've modified the code. Now the pool can be configured (second template argument of tp::pool) to use recursive invokation of tasks or fibers in order to enable fork/join semantics. I've found that the recursive invokation is more than two times faster than using fibers (see examples recursive_fibonacci_recursive_task.cpp and recursive_fibonacci_with_fibers.cpp). The code using fibers sometimes raises an assertion in ~mutex() (used in work-stealing queue). For this reason and following the discussions I think I'll remove the support for fibers from threadpool. regards, OPliver