chtMultiRegionFoam on multiple cores, run-time increases?
 

Hello fellow foamers,

I am currently working on some heat transfer problems using the chtMultiRegionFoam solver. I want to speed up the solving process by running a decomposed case. To find out how much I would benefit from using multiple cores I tried to run a similar case in single core and multi-core mode. The results had the same quality (in terms of U, T and p), but the run time wasn't as I expected. Here are my results:

~20 000 cells
1 core -> 875s
2 cores -> 1022s


~225 000 cells
1 core -> 57046s
4 cores -> 58539s


Now I have some questions:
- is it possible, that I didnt use enough cells, per core? I read at about 50 000/core the time will reduce.
- is it important to decompose the case in a special way? I used the simple method.

Thank you already,
Vince.

Hi!


Try with scotch method. It will tries to decompose the case on a way that the communication between the processors is minimal.
Also a renumberMesh can help.


Based on my experiences OF is scaling pretty well.

scotch
 

Thank you for your reply simrego.

I decomposed with scotch and am currently running the case. It might take some time till I can update, as I only work with OF on one day per week.

Greetings