[petsc-users] Schur complement preconditioner

[Matthew Knepley]

On Tue, Oct 1, 2019 at 3:33 PM Salazar De Troya, Miguel via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hello,
>
>
>
> I am trying to understand the difference between the commands
> -pc_fieldsplit_schur_precondition and -fieldsplit_1_pc_type when we use
> -pc_fieldsplit_type schur. The first one I know from the manual that it is
> the preconditioner for the Schur complement matrix. The second command
> seems to also be a preconditioner for the Schur complement matrix, as said
> here
> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCFIELDSPLIT.html
> , what’s the motivation to have the first command then ? I might not be
> understanding some of the mechanics of PETSc
>

The first command determines what will be used as the _preconditioning
matrix_. The second command determines what preconditioner
will be built from the preconditioning matrix.

  Thanks,

    Matt


> Thanks
>
> Miguel
>
>
>
> Miguel A. Salazar de Troya
>
> Postdoctoral Researcher, Lawrence Livermore National Laboratory
>
> B141
>
> Rm: 1085-5
>
> Ph: 1(925) 422-6411
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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