It gets more interesting when you have a large data set that's required for the computation, but as you compute, you may discover partial solutions that can be

It gets more interesting when you have a large data set that's required for the computation, but as you compute, you may discover partial solutions that can be cached and used by other workers. So not only a large read-only data set, but also a read-write cache used by all workers. This sort of thing is relatively easy with threads, but basically impossible with multiprocessing.