Newsgroups: comp.parallel.mpi
From: llewins@msmail4.hac.com (Lloyd J Lewins)
Subject: Re: Use of MPI_Gatherv
Organization: Hughes Aerospace Electronics Co.
Date: Fri, 03 Nov 1995 09:06:14 -0800
Message-ID: <llewins-0311950906140001@x-147-16-95-58.es.hac.com>

In article <47b99b$78i@gaia.ns.utk.edu>, pena@cs.utk.edu wrote:

> I'd like to know if there are any way to specify, in the MPI_GATHERV
> function, a displacement (displ) of size smaller than the lenght of the
> data type of recv buffer.

No you cannot specify any displacement other than multiples of the extent
of the recv type.
 
> And anybody knows why if, in the MPI_GATHERV, you can specify differents
> sizes and displ for the buffers received, then why you cannot specify
> differents data types for each one of these buffers?

I believe this was an oversight by the MPI Forum. I have a proposal to add
a set of functions (MPI_XXXS), which will allow seperate specification of size,
type and displs for each process, displs being in bytes. This should be fully
general, and meet your needs.

Note: in the MPICH implementation, MPI_Gatherv is a fairly simple function. You
could roll your own MPI_Gathers until MPI-2 becomes a standard.

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Lloyd J Lewins                                  Mail Stop: RE/R1/B507
Hughes Aerospace and Electronics Co.            P.O. Box 92426
                                                Los Angeles, CA 90009-2426
Email: llewins@msmail4.hac.com                  USA
Tel: 1 (310) 334-1145
Any opinions are not neccessarily mine, let alone my employers!!

