build problem with ocen model

[cbasu@nsc_liu_se]

Hi,

I am testing ccsm4 on linux cluster using openmpi and intel compiler for f19_g16 with B_1850_CN. I was able to build and run ccsm4 on 448 procs with 192 procs for ocen model.

When I try to build ccsm4 with pe count for ocen model as 200. I get the following error

pop decomp not set for gx1v6 on 200 x 1 procs

What is the meaning of this error?

I also tried to use openmp for ocean model. However although the model compiles at run time the ocean model does not spawn multiple threads. What is the reason for that?

Regards,

Chandan Basu
National Supercomputer Center
Linköping University
S-581 83 Linköping
email: cbasu@nsc.liu.se

 

[njn01]

As you discovered, the number of processors that can be assigned to the cesm active ocean model (pop2) is restricted to certain values. In your example, the gx1v6 pop2 can be assigned to 192 pes, but not 200. While it is theoretically possible to assign cesm pop2 to 200 processors, the domain size is such that this decomposition would result in domain "padding" and therefore extra, unnecessary computations, so we do not support this as an out-of-the-box configuration.

Supported decompositions for the gx1v6 grid include, among others, 192, 240, and 256. If you really want to assign gx1v6 pop2 to 200 processors, you can do this by adding the appropriate lines to your $CASE/Tools/Template/pop_decomp.xml file. Presently, this tool is undocumented, but you can probably figure out how to modify it by looking at the file contents.

When modifying the number of pes assigned to the ocean model in your $CASE, you should follow the steps outlined in the cesm User's Guide.