Subject: latest draft

From: [email-masked] (David Walker)
Date: Mon, 28 Jun 1993 11:46:44 -0400

Since I missed last week's Dallas meeting many of the issues below concerning
the June 24 draft of the groups, contexts, and communicators proposal
may already have been dealt with.

1. MPI_COMM_HOST, MPI_COMM_PARENT. Since the MPI process model does not
   currently include the idea of a host or parent I think these should be
   omitted. If and when the next generation of MPI gets off the ground
   communication with host and parent will become an issue, but I think we
   should defer talking about such things until then.

2. Can anyone give me an example using MPI_TRANSLATE_RANKS?

3. Do we need flatten/unflatten routines for both groups and communicators?
   Am I right in assuming that flatten/unflatten routines are provided as
   more efficient ways of disseminating group/communicator information than
   publish abd subscribe?

4. In the union, intersection and difference set operations, what assumptions
   are being made about the relationship between the ranks in the parent
   and child groups? In my opinion, MPI should not specify any relationship.
   So if you form the union of 2 groups you just get a third group and ranks
   in this latter group bear no relation to those in the former 2 groups. If
   order is really important, perhaps we should have an MPI_GROUP_CONCATENATE
   routine.

5. I would prefer to use MPI_FREE rather than MPI_GROUP_FREE, in the interests
   of limiting the number of routines.

6. I would prefer a single routines for partitioning, permuting, and copying
   groups, rather than separate MPI_COLL_SUBGROUP and MPI_COLL_GROUP_PERMUTE.

7. What is MPI_CONTEXTS_RESERVE for? Any examples?

8. Am I correct in inferring from MPI_COMM_MERGE that the concept of a C2
   communicator no longer exists in MPI? I guess I would have preferred
   all communicators to be of the form:

		local_group,
		remote_group,
		send_context,
		recv_context

   so that if local_group=remote_group we have intragroup communicator.

9. The example on page 10 contains errors. Also I think all examples
   should be complete programs or routines. These are much easier to
   follow than disembodied code fragments.

10.We still nedd to have more example codes to justify routines related to
   groups and communicators. These routines are likely to be very
   frightening to many people.

Sorry if many of these points have already been discussed, but I would 
appreciate it if someone would bring me up to speed.

David