[Beowulf] MPICH question

Rusty Lusk lusk at mcs.anl.gov
Wed Feb 23 00:12:17 EST 2005


From: John Lau <cflau at clustertech.com>
Subject: [Beowulf] MPICH question
Date: Tue, 22 Feb 2005 09:30:29 +0800

> Hi,
> 
> I have a question on the number of processes spawned by MPICH. I am
> using MPICH 1.2.5.2 --with-device=ch_p4. When I use mpirun -np 4 to
> start a mpi process, total 8 processes will be spawned. But only 4
> processes have loadings on CPUs. I would like to know if it is the
> correct behavior of MPICH? And what's the use of the 4 no-loading
> process? Thank you.

The other 4 processes are "listener" processes that permit dynamic
creation of connections as they are needed.  What you see is the correct
behavior.  We recommend that MPICH1 users switch to MPICH2.

Regards,
Rusty Lusk
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