[petsc-users] Correct use of PCFactorSetMatOrderingType

[Edoardo alinovi]

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
Tel: +39 010 353 2540




Il giorno mar 6 nov 2018 alle ore 16:04 Zhang, Hong <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
>> Tel: +39 010 353 2540
>>
>>
>>
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