:-)
>shouldn't a high-quality application
>just manage a small pool of communicators for the best performance?
Yup. In MPI-1, the story was that a high-qual impl. would pre-allocate
N context IDs at comm-create time, allowing the next N-1 comm-dup to be
lightweight (and reuse the context IDs, etc.).
So a new function isn't needed. If the thinking is that this function
will help push implementors to do this kind of context ID mgmt, Eric
just showed how futile that can be.
To make things really "fun" for users, implementors could make this new
function very heavyweight (N allreduce), while optmizing good old
MPI_Comm_dup() to pre-allocate context IDs. This would help push users
to stick to good MPI-1 functions. :-) :-) :-)
--Raja
-=-
Raja Daoud Hewlett-Packard Co.
raja@rsn.hp.com Convex Division