[R] newbie question on snow/Rmpi

[Dirk Eddelbuettel]

On Mon, Dec 15, 2008 at 01:16:46PM -0500, Whit Armstrong wrote:
> I have a network of four machines set up.  I'm having trouble spawning
> my slaves on these machines.
> 
> All the examples I have found so far use makeCluster with type="MPI",
> and I guess I'm missing some kind of cluster configuration in my
> environment variables because all my clusters are formed on the
> machine where my initial session is running.
> 
> Can anyone refer me to a link that illustrates how to set up the
> environment for MPI (listing node names, number of slots, etc) that
> will allow the makeCluster command take advantage of the other nodes?

It depends on which MPI library you use. I like Open MPI.

> Thanks,
> Whit
> 
> 
> simple example:
> 
> library(Rmpi)
> library(snow)
> 
> cl <- makeCluster(2, type = "MPI")

You must call R (or r or Rscript) 'inside' orterun (or mpirun) which
allows you to set hostnames on that invocation.  See my UseR 2008
tutorial for some examples.  

Dirk

-- 
Three out of two people have difficulties with fractions.