i want to use a cluster to run a space simulation im working on so does unity support message passing interface. if not, then is there a way to use the cpu power of a few pcs to run a simulation or a game.
Not natively. If you have the Pro version, you can use one of the MPI wrappers to access an MPI C library. Mono itself mentions two libraries you could use:
Both are wrapper around the native MPI libraries that come with today’s operating systems. MPI.NET works on both Unix and Windows systems, MPAPI seems to be Windows only. If you have a Mac, then as usual, you are probably out of luck.