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Subject: Re: [OMPI users] Newbie question
From: Tena Sakai (tsakai_at_[hidden])
Date: 2011-01-11 01:06:18


Thanks for your reply.

I am afraid your terse response doesn’t shed much light. What I need is “hosts”
parameter I can use to mpi.spawn.Rslaves() function. Can you explain or better
yet give an example as to how I can get this via mpirun?

Looking at mpirun man page, I found an example:
  mpirun –H aa,aa,bb ./a.out
and similar ones. But they all execute a program (like a.out above). That’’s not
what I want. What I want is to spawn a bunch of R slaves to other machines on
the network. I can spawn R slaves, as many as I like, to the local machine, but
I don’t know how to do this with machines on the network. That’s what “hosts”
parameter of mpi.spawn.Rslaves() enables me to do, I think. If I can do that, then
Rmpi has function(s) to send command to each of the spawned slaves.

My question is how can I get open MPI to give me those “hosts” parameters.

Can you please help me?

Thank you in advance.

Tena Sakai

On 1/10/11 8:14 PM, "pooja varshneya" <pooja.varshneya_at_[hidden]> wrote:

You can use mpirun.

On Mon, Jan 10, 2011 at 8:04 PM, Tena Sakai <tsakai_at_[hidden]> wrote:

I am an mpi newbie. My open MPI is v 1.4.3, which I compiled
on a linux machine.

I am using a language called R, which has an mpi interface/package.
It appears that it is happy, on the surface, with the open MPI I installed.

There is an R function called mpi.spawn.Rslaves(). An argument to
this function is nslaves. I can issue, for example,
  mpi.spawn.Rslaves( nslaves=20 )
And it spawns 20 slave processes. The trouble is that it is all on the
same node as that of the master. I want, instead, these 20 (or more)
slaves spawned on other machines on the network.

It so happens the mpi.spawn.Rslaves() has an extra argument called
hosts. Here’s the definition of hosts from the api document: “NULL or
LAM node numbers to specify where R slaves to be spawned.” I have
no idea what LAM node is, but there is a funciton called lamhosts().
which returns a bit verbose message:

  It seems that there is no lamd running on the host compute-0-0.local.

  This indicates that the LAM/MPI runtime environment is not operating.
  The LAM/MPI runtime environment is necessary for the "lamnodes" command.

  Please run the "lamboot" command the start the LAM/MPI runtime
  environment. See the LAM/MPI documentation for how to invoke
  "lamboot" across multiple machines.

Here’s my question. Is there such command as lamboot in open MPI 1.4.3?
Or am I using a wrong mpi software? In a FAQ I read that there are other
MPI software (FT-mpi, LA-mpi, LAM-mpi), but I had notion that open MPI
is to have functionalities of all. Is this a wrong impression?

Thank you for your help.

Tena Sakai
tsakai_at_[hidden] <>

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