[petsc-users] Correct use of PCFactorSetMatOrderingType

[Zhang, Hong]

Edoardo:
Interesting. I thought it would not affect performance much. What happens if you use -sub_pc_type lu'?
Hong

Dear Hong and Matt,

thank you for your kind replay. I have just tested your suggestions and applied " -sub_pc_type ilu -sub_pc_factor_mat_ordering_type nd/rcm" and, in both cases, I have found  a deterioration of performances with respect to doing nothing (thus just putting default PCBJACOBI). Is it normal? However, I guess this is very problem dependent.
------

Edoardo Alinovi, Ph.D.

DICCA, Scuola Politecnica
Universita' di Genova
1, via Montallegro
16145 Genova, Italy

email: edoardo.alinovi at dicca.unige.it<mailto:edoardo.alinovi at dicca.unige.it>
Tel: +39 010 353 2540




Il giorno mar 6 nov 2018 alle ore 16:04 Zhang, Hong <hzhang at mcs.anl.gov<mailto:hzhang at mcs.anl.gov>> ha scritto:
Edoardo:
You can test runtime option '-sub_pc_factor_mat_ordering_type' and use '-log_view' to get performance on different orderings, e.g.,petsc/src/ksp/ksp/examples/tutorials/ex2.c:
mpiexec -n 2 ./ex2 -ksp_view -sub_pc_type ilu -sub_pc_factor_mat_ordering_type nd

I do not think the ordering inside block for ilu would affect performance much. Let us know what you will get.
Hong

Dear users,

I have a question about the correct use of the option  "PCFactorSetMatOrderingType" in PETSc.

I am solving a problem with 2.5M of unknowns distributed along 16 processors and  I am using the block jacobi preconditioner and MPIAIJ matrix format. I cannot figure out if the above option can be useful or not in decreasing the computational time. Any suggestion or tips?

Thank you very much for the kind help

------

Edoardo Alinovi, Ph.D.

DICCA, Scuola Politecnica
Universita' di Genova
1, via Montallegro
16145 Genova, Italy

email: edoardo.alinovi at dicca.unige.it<mailto:edoardo.alinovi at dicca.unige.it>
Tel: +39 010 353 2540


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