[Wrf-users] dynamic load balancing in RSL_LITE

John Michalakes john at michalakes.us
Fri Nov 13 06:57:01 MST 2009

Dear Preeti,

RSL_LITE does not support dynamic load balancing. Years ago, a version 
of MM5 called MM90 was developed and tested that included an 
experimental version of dynamic load balancing.  See: 

The approach and results, while interesting from a computer science 
research point of view, were never sufficiently compelling to justify 
the cost and difficulty of developing and maintaining this capability 
for the distributed-memory parallel MM5 or the WRF model which followed 
it.  In addition, the old RSL code had some unacceptable limits on 
domain size and scalability to large numbers of processors. Therefore, 
RSL was replaced by the much simpler but more scalable RSL_LITE parallel 
layer that is distributed with WRF today. Physics load imbalance remains 
a nuisance.  Please feel free to contact me if you have any questions.


Preeti wrote:
> Hi
> I have a question related to dynamic load balancing in WRF. I am using
> WRFv3.0.1. The documentation of WRFv3
> http://www.mmm.ucar.edu/wrf/users/wrfv3/updates.html mentions the
> following -
> * Full RSL_LITE support for nesting, transposes, periodic BC’s, etc.
> RSL communication package has been retired in V3
> However I have read the paper by John G. Michalakes "RSL: A Parallel
> Runtime System Library for Regional Atmospheric Models with Nesting"
> which talks about Dynamic Load Balancing in RSL by re-mapping. I could
> not find any RSL_LITE documentation which talks about re-mapping to
> new processors due to load imbalance.
> Since RSL_LITE replaces RSL in WRF, I wanted to know if there is any
> similar feature implemented in RSL_LITE in WRF for dynamic load
> balancing?
> Appreciate your help very much.
> Thanks
> Preeti
> _______________________________________________
> Wrf-users mailing list
> Wrf-users at ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/wrf-users

John Michalakes, Software Engineer        michalak at ucar.edu
NCAR, MMM Division                   voice: +1 303 497 8199
3450 Mitchell Lane                     fax: +1 303 497 8181
Boulder, Colorado 80301 U.S.A.        cell: +1 720 209 2320

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