Newsgroups: comp.parallel.mpi
From: Nick Nevin <nevin@alex.osc.edu>
Subject: Re: MPI_PROC_NULL & LAM
Organization: Ohio Supercomputer Center
Date: 10 May 1996 08:31:04 -0400
Message-ID: <vn2zq7gsoaf.fsf@alex.osc.edu>


> these calls make extensive use of MPI_PROC_NULL as defined in the MPI
> standard (1.1, sec 3.11). Unfortunately this is not consistently
> implemented in the LAM 6.0 RTS. Is there anybody who already encountered
> this problem and has fixed it ? 

The problem has been fixed and I will be releasing a patch shortly.

> Second of all, I do remember a discussion on MPI_PROC_NULL and a not
> well defined behaviour concerning invalid tags and so on. Seems to me
> that even MPI_PROC_NULL is not unambiguously defined.

Some implementations may return an error if an invalid tag is given in a
send to MPI_PROC_NULL while others may take the view that since the tag
is meaningless in this case it can be ignored and the send succeeds. This
may be a problem for theorists but in practice is of little
consequence. Just use proper tags in all your calls.

Regards Nick.

-=-
Nick Nevin				nevin@osc.edu
Ohio Supercomputer Center		http://www.osc.edu/lam.html


