On Jul 13, 2005, at 3:16 AM, Lei_at_ICS wrote:
> I am given a Matlab+C program for me to parallelize. What I need to do
> is to parallelize a C routine that is called by another C routine,
> which in
> turn is called from Matlab. There are large and complicated C data
> structures that are passed in and out the C routine being parallelized.
>
> My question is: is there a way to spawn MPI processes from a non-MPI
> process, and at the same time pass in and out C data structures between
> the parent sequential and the child MPI processes.
So that's 2 questions:
1. can a non-MPI process spawn MPI processes: sort of. However, it's
probably easiest if your non-MPI process simply calls MPI_INIT and
becomes an MPI process (i.e., you don't have to launch it via mpirun --
if it calls MPI_INIT, it will simply get an MPI_COMM_WORLD size of 1,
and then call MPI_COMM_SPAWN from there to launch more MPI processes).
Other people have done this with Matlab before (indeed, there is a
package out there with MPI bindings for Matlab MEX), and there are
definitely some issues that need to be thought out first. Search the
LAM mailing list archives -- this stuff has been discussed extensively
before.
2. Can you pass C structures from the parent to the child: if you
follow the suggestion in #1, there's nothing to pass -- Matlab itself
becomes the parent MPI process; then you use standard MPI send/receive
semantics to pass data from the Matlab script (or C routine) to the
spawned processes. If you use a different mechanism, then you can use
traditional Unix IPC mechanisms to pass the data (pipes, files, local
sockets, shared memory, etc.).
Hope that helps.
--
{+} Jeff Squyres
{+} jsquyres_at_[hidden]
{+} http://www.lam-mpi.org/
|
