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Subject: [OMPI users] 100% CPU doing nothing!?
From: Douglas Guptill (douglas.guptill_at_[hidden])
Date: 2009-04-22 10:26:25

Hi Ross:

On Tue, Apr 21, 2009 at 07:19:53PM -0700, Ross Boylan wrote:
> I'm using Rmpi (a pretty thin wrapper around MPI for R) on Debian Lenny
> (amd64). My set up has a central calculator and a bunch of slaves to
> wich work is distributed.
> The slaves wait like this:
> mpi.send(as.double(0), doubleType, root, requestCode, comm=comm)
> request <- request+1
> cases <- mpi.recv(cases, integerType, root, mpi.any.tag(),
> comm=comm)
> I.e., they do a simple send and then a receive.
> It's possible there's no one to talk to, so it could be stuck at
> mpi.send or mpi.recv.
> Are either of those operations that should chew up CPU? At this point,
> I'm just trying to figure out where to look for the source of the
> problem.

Search the list archives
for "100% CPU" and you will get lots to look at.

I had a similar problem with a FORTRAN program. With the help of Jeff
Squyres and Eugene Loh I wrote a solution: user-written MPI_Recv.c and
MPI_Send.c which I load them with my application, and the MPI problem
"100% CPU usage while doing nothing" is cured.

The code for MPI_Recv.c and MPI_Send.c is here: