[mpich-discuss] Hello !

Gustavo Correa gus at ldeo.columbia.edu
Sun Oct 30 12:23:05 CDT 2011

Hi Alexander

You need to be more specific about the problem, send the error messages, etc.

In any case ...

Typically, if you want to  run MPICH2 on several machines
you must setup passwordless ssh across them, and *any* machine
should be able to connect to *any other* machine via ssh,  no password requested.
I.e. pairwise passwordless ssh connection.
MPICH2 will work over Ethernet [or Gigabit Ethernet], but also on a few other interconnects,
although not Infiniband as far as I know.
For Infiniband use MVAPICH2 or OpenMPI.

In addition, you need to either install MPICH2 on all machines, preferably in 
directories with the same name, OR, you could install MPICH2 in a single machine,
in a directory that is visible to all machines [e.g. via NFS].
In either case you must check if all machines have the MPICH2 functionality.

Moreover, you must setup your environment variables [at least PATH, but maybe also
LD_LIBRARY_PATH] in a consistent way on all machines, and they should point to
the MPICH2 executables [mpicc, mpiexec, etc] and libraries.
It is very common to have other MPI installed and get things mixed up, PATHs tangled, etc.
Typically this setup can be done in the user's .profile or .bashrc, or .[t]cshrc file.
If you have a single home directory shared via NFS on all machines, then you edit only
one file.  If the home directories vary by machine, you need to edit all of them.
There are other ways to setup the environment, but the above is a simple one.

Fourth, you need to have a machinefile that names/describes correctly 
the machines you are using.

Fifth, don't get confused by old web pages out there of perhaps by the Fluent user guide 
that may talk about mpd and things the like.
Mpd was the older MPICH2 launcher.
The current MPICH2 launcher is Hydra.
So, you need to use it instead of mpd.

Sixth:  I must have forgotten something, but this initial setup always has bumps and humps.
Give it a try, tell the list what happens, send the error messages to the list.

I hope this helps,
Gus Correa

On Oct 29, 2011, at 7:19 PM, Alexandar Duren wrote:

> Hello,
> I'm Alexandar. I've a few questions to know about MPI. How I can setup the MPI library so that it can be ran parallel computing. I used Ansys Fluent to run parallel processing by using MPI as library. I already tried to use that software, but at the end it fails to detect another computers. Thank you fo your consideration of reading my email.
> Regards,
> Alex
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