I don't know, but when I was playing with finite difference code as an undergrad in Physics, all of the docs I could find (it was a while ago, though) assumed that I was going to use MPI to run a distributed workload across the university's supercomputer. My needs were less, so I just ran my Boost.Thread code on the four cores of one node.

What if you had a single server with a zillion cores in it? Maybe you could take some 15 year old MPI code and run it locally -- it'd be like a mini supercomputer with an impossibly fast network.