Message-Id: <36E789BC.5D97CBCC@etnus.com>
Date: Thu, 11 Mar 1999 09:15:40 +0000
From: James Cownie <jcownie@etnus.com>
Organization: Etnus, Inc.
Mime-Version: 1.0
Newsgroups: comp.parallel.mpi
Subject: Re: send/recv
References: <7c4b4e$ag0$1@nnrp1.dejanews.com> <7c66ks$f99$1@vvv.srcc.msu.su>
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Xref: ukc comp.parallel.mpi:4729


Alexander N. Andreyev wrote:
> 
> In my humble opinion,
> with MPI_Send you can pass any contiguos data structures, just using
> MPI_CHAR as datatype and sizeof(Your_Structure_Type) as message size. :)) No
> need for special datatype management, of course, if the structure doesn't
> contain any pointers.

This will work *provided* that you are in a homogeneous environment
where
all of your MPI processes are running on machines with the same data
format
representation.

It will definitely fail badly if you try to use this trick for
transferring data
between machines with different data representations (endianness, fp
format etc).

The reason for going to the trouble of explaining the true content of
your
messages to MPI is so that it can ensure that the semantics of your
message
is preserved, rather than just the bits.

So, as usual, if you want real portability you need to do a little more
work.

-- Jim 

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