Dear FreeFem users, when I run FreeFem in parallel on e.g., 5 processes, it also starts 10 sleeping processes. These processes seem to consume memory. Should I be worried about this? That is the reason for this? See also the attached image. I experience this behaviour on ubuntu 18.04, either mount…

I must admit, I have no idea what the FreeFem compilation process does, so it is likely what I am not looking at the right place. I am sending you the config.log file from the FreeFem-sources directory. Could you please help me out how can i check the BLAS version? config.log (347.1 KB)

It’s in the file you sent or in PETSc configure.log. But it looks alright. I think it’s OK, are you getting bad performance?

The speed of the calculation is fine I suppose. I am trying out the steady-state mAL preconditioner NS solver , and I seems to run out of memory quite fast (at least compared to other commercial CFD software with about the same mesh size). I found that changing the last part of string paramsV = "-k…

What’s the size of the problem?

This run just dpes not run out of ram on a virtual machine with 12 GB ram. number of triangles: 244925,number of vertices: 47183 total ndof: 1183721 (in FreeFem numbering) I am also sending you the output of the -log_view option. Nonlinear-solver_Re350.log (14.3 KB)

This is a tiny problem, why not use plain LU?

For this mesh size the mAL preconditioned GMRES method seems to outperform plain LU factorization considering lower memory usage, but LU is slightly faster. The thing is, we want to run this on our desktop machine, or even if we will use a cluster, we would like to use only a few processes (4-6/case…

If you’ll stick to low process counts, you could try PCASM + PCLU for subdomain solvers (maybe with MUMPS instead of the default PETSc LU factorisation). For the sleeping processes, I don’t know, sorry.

Thanks for the helpful comments. Just to be sure, you mean by PCASM+PCLU for the subdomain solver the following: -pc_type asm -pc_asm_overlap 1 -sub_pc_type asm -sub_sub_pc_type lu -sub_sub_pc_factor_mat_solver_type mumps? (this seems to run and converge)

Number of processes and memory usage

General Discussion

aszaboa May 20, 2022, 1:16pm 16

Regarding the additional sleeping processes, changing openmpi to mpich helped; see this post for more detail.

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Number of processes and memory usage

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