From octave-maintainers-request at bevo dot che dot wisc dot edu Thu Nov 21 10:51:23 2002
Subject: Re: Patching Octave-MPI
From: Andy Jacobson <andyj at splash dot princeton dot edu>
To: octave-maintainers at bevo dot che dot wisc dot edu
Date: 21 Nov 2002 11:51:19 -0500

>>>>> "Paul" == Paul Kienzle <pkienzle at jazz dot ncnr dot nist dot gov> writes:

    Paul> There are a variety of approaches to parallelism which have
    Paul> been done in matlab m-files and mex-files.  E.g.,

Alex Verstak raised an interesting point last year: he said that the
MPI standard requires that MPI_Init() be fed the *original* argv and
argc.  (Yes, it is arguably a silly requirement.)  With at least MPICH
apparently, MPI_Init() would not work from a .oct file.  See:

http://www.octave.org/mailing-lists/help-octave/2001/141

Later however, Alex apparently did get it running:

http://www.octave.org/mailing-lists/help-octave/2001/218

So perhaps a .oct solution will work.

Note however that the parallelized Matlab solutions all are guided by
two facts: (1) they cannot modify the source code so the
parallelization has to work via .mex/.m files, and (2) due to the cost
of multiple Matlab licenses, there may be implicit assumptions about
how many instances are running in a given MPI application.  There may
be hidden performance issues.

It should a pretty trivial matter to determine whether or not the user
wants a parallel or traditional application when she starts octave.
Perhaps something as simple as "octave --mpi-server" or "octave
--mpi-client".  Then we call MPI_Init() (and later MPI_Finalize()) as
appropriate.  That is just about all that is required from the main
code; the rest could naturally be moved to .oct.

        Regards,

               Andy

-- 
Andy Jacobson

arj at gfdl dot gov

Program in Atmospheric and Oceanic Sciences
Sayre Hall, Forrestal Campus
Princeton University
PO Box CN710 Princeton, NJ 08544-0710 USA

Tel: 609/258-5260  Fax: 609/258-2850