[R-sig-hpc] Rmpi on Mac OS X 10.5.8 dual core machine

Ross Boylan ross at biostat.ucsf.edu
Sat Dec 12 01:01:05 CET 2009

On Wed, 2009-11-18 at 17:09 -0200, Benilton Carvalho wrote:
> Hi,
> I decided to experiment with Rmpi on my dual core machine (Mac OS X  
> 10.5.8).
> So, I try the usual:
> library(Rmpi)
> mpi.spawn.Rslaves()
> and let R "sit there"... I expected the R process to be idle, but for  
> my surprise it uses, at least, 70% of CPU.
> Is this an expected behavior? 
I'd expect 100%, but that's based on a Linux cluster.
OMPI does busy waiting, i.e., it runs in a tight loop checking for data.
So it uses lots of CPU even when it's doing nothing.

The developers made this choice to increase the responsiveness on MPI,
based partly on the assumed target use-case involving a cluster in which
nodes were allocated entirely to the job running under MPI--i.e.,
nothing else we need the CPU.

> I'm currently assuming I'm missing  
> something obvious.
> Also, on a Mac OS X system, is Rmpi supposed to work without LAM?
> Hao Yu's page makes me think it is a requirement, but, on my system,  
> it found OpenMPI, so I didn't install LAM....
> Comments,
> b
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