Subject: Re: copying ?

From: Ian Glendinning <[email-masked]>
Date: Tue, 7 Sep 93 16:00:31 BST

> From: [email-masked]

> I have a couple of questions about copying groups and communicators.
> 
> 1. The current context chapter says that MPI_GROUP_DUP is "essential to
>    the support of virtual topologies".  I do not understand this, and
>    the examples are of no help.  (Only one example calls MPI_COMM_DUP,
>    and no example calls MPI_GROUP_DUP.)  
> 
>    Can someone please explain why MPI_GROUP_DUP is considered so
>    important, and perhaps provide an illustrative example?

I suspect, as you appear to, that it is not `essential'.  Remember that the
process topologies proposal, as it stands, has groups everywhere as arguments
to routines, where there possibly ought to be communicators.  Until the last
meeting, the groups and contexts proposal was in such a state of flux, that
it wasn't clear what precisely ought to be there, but then Rolf wasn't at the
last meeting to advise on what changes to make, and the second reading of that
chapter was a bit of a shambles.  It could be that one of the COMM_DUP
routines is actually what's needed now.  On the other hand, if we're going to
have local manipulation of groups, then I suppose you ought to be able to
duplicate them.
   Ian
--
[email-masked]        Ian Glendinning
Tel: +44 703 593368                  Dept of Electronics and Computer Science
Fax: +44 703 593045                  University of Southampton SO9 5NH England