On May 5, 2008, at 1:28 PM, Supalov, Alexander wrote:

Thank you. We can actually introduce what you propose, possibly with a query function to make it still easier to live with, as early as in MPI 2.2, as a subset precursor. Judging by the discussion in Chicago, subsets may not need much more than that in the end, possibly with a little more flags and semantics added in MPI-3.

The reservation against 32- (or for that matter, 64-) bit limitation is the only one I have at the moment. Not being able to attach assertions to communicators, etc. may be missed by some advanced programmers, but here we need to be pragmatic: who will ever want to go that deep?

Libraries that build on top of MPI may want to. This was one of the prime motivations for communications, right? (private/safe communications) As Quincy stated in Chicago and on the mailing list (IIRC), what if a top-level app sets an assertion that a library using MPI can't live with? Being able to set them per-communicator might alleviate that issue. -- Jeff Squyres Cisco Systems