[Wrf-users] Benchmarking problems

[Andrew Porter]

Hi Bart,
>
> &domains
> ...snip...
>   numtiles                            = 1,
>   nproc_x                             = 3,
>   nproc_y                             = 2,
>   num_metgrid_levels                  = 40,
> /
>
> I set OMP_NUM_THREADS to 6 in my run script that calls wrf.exe.
>
> And yet, when I look in the resulting wrf.out file I see:
>
>   WRF NUMBER OF TILES FROM OMP_GET_MAX_THREADS =   6
>   WRF NUMBER OF TILES =   6
>
> Hey! I told you to use 1 tile and split it 3 by 2!
>
I think nproc_x and nproc_y only applies to MPI processes. By telling it 
to use only 1 tile I think you'll end up with 5 threads not doing 
anything! You can leave ntiles out to have it set to OMP_NUM_THREADS by 
default or you can set it > OMP_NUM_THREADS to see whether that fits 
things into cache more successfully.

God bless,

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