[vienloer]

I tried to use 20 cores for simulation, but my cpu utilization was just 5%. what should I do to increase CPU usage? My cpu has 16 logical cores and 32 physical cores.


File "decomposeParDict",

numberOfSubdomains 20;

method simple;

coeffs
{
n (2 10 1);
}


The code,
~$ mpirun -np 20 icoFoam -parallel

Thank you for help!

[LeeRuns]

Try to have number of cores same as number subdomains. Reduced cross core communication.

[cyss38]

How many cells do you have in the mesh?
The recommendation and the tests that I have been able to perform show that a good choice is to have about a minimum of 15,000 cells per process to be efficient.
Thus for 20 cores, the mesh would have to consider 300,000 cells.
In addition, I recommend the scotch mesh decomposition method.

[LeeRuns]

Also pretty important to have cells evenly distributed. If one section is way complex for solver the use more cells there, but make domain smaller. Sorry about wording typing fast between tasks....try to think about your geometry and make sure that each section of the domain has a similar workload (complexity, number of cells)

Also is it really cpu that is holding you back I often find that goal io is pretty tough on machines with OF

[vienloer]

Thank you for your reply. So the total mesh number is important，right? I just have 10,000 meshes, the core number can not be 20 or more, if I still try to use too many cores, the system will break, right?

[vienloer]

Thank you! I will try more cases to learn more.