[Wrf-users] WRF Nest scalability

[Andrew Porter]

Hi Preeti,
>
> I have a 21km parent domain of 348  X 247 and a nest domain of 7km
> resolution with dimension of 109 X 136. I am currently running it on
> upto 90 processors but I find that the solve time of parent scales with
> adding more processors whereas the solve time of nest does not scale.
> The interconnect is Infiniband. Does anyone know the reason for this?
>
With 90 processors (presumably decomposed into a 9 x 10 grid) the nested 
domain will only have about 10 x 10 points per processor. Increasing the 
number of processors beyond this isn't going to improve things because 
the workload is so small that any improvement will be over-shadowed by 
the increase in communications.

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