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Subject: Re: [OMPI users] More newbie question: LD_LIBRARY_PATH
From: Gus Correa (gus_at_[hidden])
Date: 2011-01-12 21:30:10

Tena Sakai wrote:
> Thank you, Gus.
> I agree with what you say about location of OpenMPI software.
> Indeed, /usr/local is nfs-mounted to all cluster nodes, albeit
> a bit unfortunate name "local." If/when I have a chance to
> Set up machines, I will make local really local to each node.
> Regards,
> Tena Sakai
> tsakai_at_[hidden]
> On 1/12/11 4:20 PM, "Gus Correa" <gus_at_[hidden]> wrote:
>> Tena Sakai wrote:
>>> Hi,
>>> On a FAQ page (
>>> (under 1. What pre-requisites are necessary for running an Open MPI
>>> job?), I see an example
>>> of LD_LIBRARY_PATH environment variable:
>>> LD_LIBRARY_PATH: /opt/openmpi/lib
>>> When I compiled the source, a directory /usr/local/lib/openmpi was
>>> generated (with many
>>> files in it). Given that, do I set D_LIBRARY_PATH to /usr/local/lib or
>>> do I set
>>> it to /usr/local/lib/openmpi?
>>> Thank you.
>>> Tena Sakai
>>> tsakai_at_[hidden]
>> To /usr/local/lib.
>> I would suggest not using the default /usr/local to install OpenMPI,
>> since it tends to be really local to the machine where you built OpenMPI.
>> This will require that you install OpenMPI on all nodes/machines if
>> you want to run programs across a network.
>> Instead, a simpler way to get OpenMPI available to all nodes,
>> although installing only on one of them (say the head node of your
>> cluster) is to do it in a directory that is shared, typically via NFS.
>> To do so, use the --prefix=/my/shared/OpenMPI/directory option of
>> the configure script.
>> There are FAQs about this too.
>> Anyway, it may depend on your environment also, whether it is a cluster
>> with a private subnet (where my suggestion is typically used),
>> a bunch of separate computers on a LAN (where the suggestion won't work
>> unless you have a shared NFS directory), or other.
>> Gus Correa
Hi Tena

Just out of curiosity, this is not really an OpenMPI issue,
and I don't know anything about Rmpi either:

How do you intend to use Rmpi?

Interactively without any resource manager control (Torque,SGI,etc),
as in a standalone PC, although utilizing several hosts via MPI?

Interactively but under resource manager control?
(E.g., Torque has the -I directive for this type of thing,
and I guess other resource managers have similar mechanisms.)

In batch mode, where a full R script runs and eventually exits?
(Which can be with or without a resource manager.)

Maybe it is something else.

Matlab (parallel or not), IDL, etc, just like R[mpi],
bring about the same type of questions for us here.

Gus Correa