[Wrf-users] The efficiency problem to run WRFV3.2.1 on a cluster with 8 nodes

[Andrew Porter]

Hi Feng,

> I'm trying to run WRF model with parallelized version with 2, 4, 8, or 16 processors on a Linux cluster with 8 nodes (each node is formed by 2-quadcores). Runs got slower with increasing the number of processors (np)! It runs correctly on all nodes but so slow. When I switch to np=2, model is running on the master node only and faster. The overall time of the simulation is bigger than for the single node run... Is the problem associated with bandwidth? network card? I have no idea. Anyone have experienced the same problem? Thanks.

Is that built in dm or dm+sm mode and how large is your model domain?

If each node on the cluster is dual quad-core then (assuming the job 
scheduler is sensible) you'll only have off-node MPI communications for 
the '16 processor' job (is that 16 MPI processes?). Therefore I doubt 
that the problem is interconnect related.

Cheers,

Andy.

-- 
Dr. Andrew Porter
Computational Scientist
Advanced Research Computing Group
Computational Science and Engineering Dept.
STFC Daresbury Laboratory
Keckwick Lane
Daresbury
WA4 4AD
Tel. : +44 (0)1925 603607
email: andrew.porter at stfc.ac.uk