Newsgroups: comp.sys.sgi.bugs,comp.parallel.mpi
From: raja@rsn.hp.com (Raja Daoud)
Subject: Re: Bugs of Array Services 3.1 on Origin2000
Organization: Hewlett-Packard Co.
Date: 9 Jul 1998 13:09:29 -0500
Message-ID: <6o310p$mag@tbag.rsn.hp.com>

Anthony Chan  <tonychan@rainbow.uchicago.edu> wrote:
>  This is a SPMD program, group_out should be different for each
>process.  The whole idea is to create one group for each process.
>I checked the return status from MPI_Comm_create(), it is OK.
>So could you explain why it is NOT allowed ?

The MPI standard says it is erroneous (page 147, lines 5-7).  To do what
you'd like to accomplish, MPI_Comm_split() is more appropriate, as Eric
Salo suggested.

MPI defines error handling mechanisms but does not mandate which errors
must be detected.  An implementation is free to decide which subset of
erroneous behavior to trap and report, and which to ignore.  In this
particular case, detecting this error requires extra communication to
gather the group memberships and compare them.  Most implementations may
choose to avoid this overhead, thus the MPI_SUCCESS return.

--Raja

-=-
Raja Daoud				Hewlett-Packard Co.
raja@rsn.hp.com				http://www.hp.com/go/mpi