StackThreads/MP: version 0.77 User's Guide

11.2: Does it subsume Pthreads?

No. It is intended to be a parallel programming tool. Pthreads, on the other hand, is intended to be both as a parallel programming tool and as a concurrent programming tool. Pthreads are sometimes used to spawn a `background' job in programs that handle asynchronous inputs. For example, GUI programs may spawn a thread to redraw the screen while another thread is listening to events. Server programs may spawn a thread to process a request from a client while another thread is servicing another. These programs create threads not so much because they want to shrink the total computation time on multiprocessors, but because they want to make them responsive to inputs. In particular, it makes sense to create a thread even on uniprocessors, as long as threads are scheduled fairly.

Threads of StackThreads/MP do not replace such threads. In particular, it does not guarantee any fairness. It only guarantees that, as long as there is any thread in the system (and the main procedure is not returned yet), it schedules a thread. However, StackThreads/MP provides a way to directly create a thread (or a group of threads) of the underlying thread package. Therefore you can comfortably mix fine-grain threads, which are cheap to create but not scheduled fairly, and threads of the underlying thread package, which are expensive to create but are scheduled fairly by the OS (see Create a Worker Group for details).