Subject: Communication contexts

From: Rusty Lusk <[email-masked]>
Date: Fri, 15 Jan 93 14:47:31 CST

| 
| On the topic of communication contexts I think (at least) 4 approaches have
| been proposed.
| 	1) Implicit communication contexts as in MPI1 controlled by push/pop.
| 	2) Explicit registration as in Zipcode
| 	3) Explicit communication contexts should be merged with explicit
|            group contexts. Since groups cannot communicate with each other
| 	   a new communication context can be created by creating a new group 
| 	   with the same members as the current group.
| 	4) Chuck Simmons of Oracle has suggested that communication contexts
| 	   are really a particular type of thread, and so can be handled
|            using existing threads packages.
| If you have any ideas, or are strongly for or against any of the above
| approaches let mpi-comm know so we can initiate a discussion of this topic.

I think that 1) contradicts our genral agreement to avoid state as much as
possible.  4) is a problem on systems that don't support threads, and we have
more-or-less agreed to be consistent with thread packages but not depend upon
them.  3) should be discussed along with the converse: that contexts rather
than groups should be the primary concept and groups defined in terms of
contexts.

David, perhaps you could create a mailing list on which this discussion can
take place, parallel to the subcommittee mailing lists, so it doesn't have to
go to the whole committee.  Thanks.

Rusty