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Subject: Re: [OMPI users] How to get started?
From: Gus Correa (gus_at_[hidden])
Date: 2008-08-15 13:05:49

Hi Anugraha, Jody, Mohd, and list

Anugraha: You should follow Jody's recommendation.
Read the OpenMPI FAQ, particularly the ones on how to install OpenMPI
compile, and run programs.

jody wrote:

Hi Anughra

Why don't you check the FAQ first:

It answers may questions and also provides instruction to install
Open-MPI and build MPI applications.
And, yes, Open-MPI works with gcc.


I could get everything to work here simply by reading the FAQ.
Read also the README file in the main directory of the distribution,
before you install. It is a good source of information too.

I am not familiar to Ubuntu, but gcc will allow you to build the OpenMPI
"C" language bindings and the compiler wrapper "mpicc",
and use it to compile and run MPI programs in C.
Besides, it will give you the MPI program launchpad "mpiexec".
This is a minimal build of OpenMPI, but may be all that you want to get

Most likely OpenMPI will also be able to build the C++ language
bindings, using g++, if present in Ubuntu.
If a Fortran 77 compiler is present (not sure if g77 is good enough for
the task, but it may),
you can build also the Fortran 77 language bindings.
Finally, if you have a Fortran 90 compiler (again, not sure if gfortran
works, but it may),
you can build the Fortran 90 language bindings.
If you have PGI or Intel Fortran you can use them instead, if you prefer.

Yes, you can use OpenMPI (and other flavors of MPI)
on a single multicore machine like your dual-core notebook.
It will use the shared memory mechanism for MPI communication.
I am not sure if the performance will be great with your processor, though.
I read reports elsewhere of low MPI performance and memory contention in
quad-core for instance.
However, performance aside, your laptop is a legitimate platform to
learn MPI programming,
without the complexities of a networked environment.
It can also be used do develop MPI code of modest size.
You can move to a cluster later, when the need for performance and
scaling comes.

You should realize that you have only two physical cores/CPUs in your
Launching jobs that start two MPI processes is perfectly safe (mpiexec
-n 2).
Launching jobs that start more than two MPI processes (say, mpiexec -n 8),
will still work if the tasks are relatively small (say, a "hello world"
but may hang if the tasks are big.

Finally, make sure your laptop has enough memory to run your MPI programs.
For small MPI programs the memory requirements should be minimal.
However, notice that each MPI process you launch has a memory footprint
of its own,
which you need to sum up (or multiply by the number of processes).
The easy way to check memory usage is through the Linux "top" utility,
while the MPI programs are running.

I hope this helps,
Gus Correa

Gustavo J. Ponce Correa, PhD - Email: gus_at_[hidden]
Lamont-Doherty Earth Observatory - Columbia University
P.O. Box 1000 [61 Route 9W] - Palisades, NY, 10964-8000 - USA
I hope this helps.
Mohd Radzi Nurul Azri wrote:
> Are you talking about single notebook or multiple? Doesn't make sense 
> to just have it single machine - unless you're building codes that 
> gonna go into a cluster.
> On Fri, Aug 15, 2008 at 6:25 PM, Anugraha Sankaranarayanan 
> <atomhouse_at_[hidden] <mailto:atomhouse_at_[hidden]>> wrote:
>     hi all,
>             I'm new to MPI.Can I install OpenMPI for my gcc?I'm using
>     Ubuntu(hardy heron) on a Intel DualCore Notebook.
>     Anugraha.S
>     _______________________________________________
>     users mailing list
>     users_at_[hidden] <mailto:users_at_[hidden]>
> -- 
> Thank you.
> Nurul Azri Mohd Radzi
>users mailing list