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On Thu, Jan 13, 2011 at 05:34:48PM -0800, Tena Sakai wrote:
> Hi Gus,
> > Did you speak to the Rmpi author about this?
> No, I haven't, but here's what the author wrote:
> in which he states:
> ...The way of spawning R slaves under LAM is not working
> any more under OpenMPI. Under LAM, one just uses
> R -> library(Rmpi) -> mpi.spawn.Rslaves()
> as long as host file is set. Under OpenMPI this leads only one R slave on
> the master host no matter how many remote hosts are specified in OpenMPI
> hostfile. ...
> His README file doesn't tell what I need to know. In the light of
> LAM MPI being "absorbed" into openMPI, I find this unfortunate.
Hmm. It has been a while that I had to compile Rmpi, but the following
works with openmpi-1.3.3, R-2.10.1:
# mpiexec -n 1 -hostfile mfile R --vanilla < Rmpi-hello.R
with a script Rmpi-hello.R like
The only unfortunate effect is that by default mpi.spawn.Rslaves()
spawns as many slaves as there are lines in the hostfile, hence you
end up with one too many processes: 1 master + N slaves. You can repair
that by using
Nprocs <- mpi.universe.size()
instead of the simple mpi.spawn.Rslaves() call.
BTW: the whole script works in the same way when submitting under torque
using the TM interface and without specifying -hostfile ... on the
mpiexec command line.
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