On Feb 8, 2010, at 2:34 PM, Lubomir Klimes wrote:
> I am new in the world of MPI and I would like to ask you for the help. In my
> diploma thesis I need to write a program in C++ using MPI that will execute
> another external program - an optimization software GAMS. My question is
> wheter is sufficient to use simply the command system(); for executing GAMS.
> In other words, will the external program "work" in parallel?
It depends on what you mean, and what your system setup is.
Calling system() may (will) cause problems if you're using a Myrinet or
OpenFabrics-based network in MPI (for deep, dark, voodoo reasons -- we can
explain if you care). If you're using TCP, you should likely be fine -- but be
aware that your resulting program may not be portable.
Calling system() in your MPI application will effectively fork/exec the
specified command. Hence, if you "mpirun -np 8 a.out", and a.out calls
system("foo"), you'll get 8 copies of foo running independently of each other.
If your project is supposed to parallelize foo, then it depends on the input /
computation / output of foo as to whether this is a good approach.
That being said, if you're just using MPI effectively as a launcher to launch N
copies of foo, note that you can use Open MPI's "mpirun" to launch non-MPI
applications (e.g., "mpirun -np 4 hostname").
> If the question is 'Yes', does someone know whether it will work also with
> LAM/MPI instead of OpenMPI?
As a former developer of LAM/MPI, I can pretty confidently say that, just like
Mac replied to your initial question on the LAM/MPI list: LAM/MPI is pretty
much dead. If you're just starting with MPI, you're much better to start with
Open MPI than LAM/MPI. :-)
--
Jeff Squyres
jsquy...@cisco.com
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