High performance computing relies on message passing -- if not pure and simple -- normally with the MPI standard. There are applications which scale at least past petaflops and 1000 cores is unexceptional.

The developers of the PETSc system wrote a position paper eschewing the typical hybrid (MPI+threading) techniques for trundling towards "exascale" -- if with MPI's shared memory support, which doesn't require cache coherence. (Apart from remote memory access, MPI departs from actor-/CSP-like systems in supporting things like collective communication (and i/o), and dynamic process management.)