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Subject: Re: [OMPI users] Problem with running openMPI program
From: Gus Correa (gus_at_[hidden])
Date: 2009-04-06 11:57:35

Hi Ankush

If I remember right,
mpirun will put you on your home directory, not on /tmp,
when it starts your ssh session.
To run on /tmp (or on /mnt/nfs)
you may need to use "-path" option.

Likewise, you may want to give mpirun a list of hosts (-host option)
or a hostfile (-hostfile option), to specify where you want the
program to run.

"/full/path/to/openmpi/mpriun -help"
for details.

Make sure your NFS export/mount of /tmp is working,
say, by doing:

ssh slave_node 'hostname; ls /tmp; ls /mnt/nfs'

or similar, and see if your program "pi" is really there (and where).

Actually, it may be confusing to export /tmp, as it is part
of the basic Linux directory tree,
which is the reason why you mounted it on /mnt/nfs.
You may want to choose to export/mount
a directory that is not so generic as /tmp,
so that you can use a consistent name on both computers.
For instance, you can create a /my_export or /work directory
(or whatever name you prefer) on the master node,
export it to the slave node, mount it on the slave node
with the same name/mountpoint, and use it for your MPI work.

I hope this helps.
Gus Correa
Gustavo Correa
Lamont-Doherty Earth Observatory - Columbia University
Palisades, NY, 10964-8000 - USA

Ankush Kaul wrote:
> Thank you sir,
> one more thing i am confused about, suppose i have 2 run a 'pi' program
> using open mpi, where do i place the program?
> currently i have placed it in /tmp folder on de master node. this /tmp
> folder is mounted on /mnt/nfs of the compute node.
> i run de progam from the tmp folder on de master node, is this correct?
> i m a newbie n really need some help, thanks in advance
> On Mon, Apr 6, 2009 at 8:43 PM, John Hearns <hearnsj_at_[hidden]
> <mailto:hearnsj_at_[hidden]>> wrote:
> 2009/4/6 Ankush Kaul <ankush.rkaul_at_[hidden]
> <mailto:ankush.rkaul_at_[hidden]>>:
> >> Also how do i come to know that the program is using resources
> of both the
> > nodes?
> Log into the second node before you start the program.
> Run 'top'
> Seriously - top is a very, very useful utility.
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