Message-Id: <373BE0EE.1FD000E4@etnus.com>
Date: Fri, 14 May 1999 09:38:06 +0100
From: James Cownie <jcownie@etnus.com>
Organization: Etnus, Inc.
Mime-Version: 1.0
Newsgroups: comp.parallel.mpi
Subject: Re: location of process 0
References: <7hfl6m$31r$1@golias.ruk.cuni.cz>
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Xref: ukc comp.parallel.mpi:5088


Martin Saturka wrote:
> 
> Hi,
> when I want to use I/O only with one process on a computer with the main
> harddisk, how can I assure, that the process with number 0 is located on
> that machine?
> Thank's, Martin.

The MPI standard says nothing about this, (because it says nothing about
how to start processes, or where they should run), *but* it does give 
you functions to determine which processes can do I/O. 

By doing Attr_get on COMM_WORLD for the MPI_IO attribute you are
returned
the rank of a process which can perform language standard I/O.

Of course, this assumes that your implementation is set up actually to
give 
you the right answer here...

If you're using MPICH, the simpler answer might be to use a procgroup
file to
place the processes explicitly.

-- Jim 

James Cownie	<jcownie@etnus.com>
Etnus, Inc.     +44 117 9071438
http://www.etnus.com