[Beowulf] WRF model on linux cluster: Mpi problem

John Van Workum jdvw at tticluster.com
Thu Jun 30 15:57:53 EDT 2005


Federico,

It could be simply a problem with the data set your are trying to process and
not the cluster. WRF is a fairly well supported and written application. If
you run faster on a single CPU, then  I suspect that particular data set is
not "easily" parallizable to run on 16. You may want to try other test cases,
one that you know will run well with 16 CPUs. Once you find it, I bet it will
crawl on 1 or 2 CPUs.

John Van Workum
TTI

>
> At 06:56 PM 6/29/2005 +0200, federico.ceccarelli wrote:
>>
>>Hi!
>>
>>I would like to get in touch with people running numerical meteorological
>>models  on a linux cluster (16cpu) , distributed memory (1Gb every node),
>>diskless nodes, Gigabit lan, mpich and openmosix.
>>
>>I'm tring to run WRF model but the mpi version parallelized on 4, 8, or 16
>>nodes runs slower than the single node one! It runs correctly but so slow...
>>
>>When I run wrf.exe on a single processor the cpu time for every timestep is
>>about 10s for my configuration.
>>
>>When I switch to np=4, 8 or 16 the cpu time for a single step sometimes its
>>faster (as It should always be, for example 3sec for 4 cpu ) but often it is
>>slower and slower (60sec and more!). The overall time of the simulation is
>>bigger than for the single node run...
>>
>>anyone have experienced the same problem?
>>
>>thanks in advance to everybody...
>>
>>federico
>>
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