[petsc-users] R: AMG Variable block preconditioner

[Matthew Knepley]

On Mon, Oct 28, 2019 at 12:37 PM Marco Cisternino via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hi Stefano,
> thanks for your interest.
> Mainly, elliptic operators both in the context of methods in NS solvers
> and in the context of mesh deformation.
> I didn't think about AMG on each block. What I was thinking about is an
> AMG preconditioner aware about the variable size blocks.
> I hope it is clearer than before.
>

If you want AMG to somehow respect the variable blocksize in coarsening, we
do not have that ability now.
Mark might know how much would be involved in changing this, but naively I
would say its a lot of work.

  Thanks,

    Matt


> Thanks,
>
>
> Marco Cisternino, PhD
> marco.cisternino at optimad.it
> _______________________________
> OPTIMAD Engineering srl
> Via Giacinto Collegno 18, Torino, Italia.
> +3901119719782
> www.optimad.it
>
>
> ________________________________________
> Da: Stefano Zampini <stefano.zampini at gmail.com>
> Inviato: lunedì 28 ottobre 2019 17:09
> A: Marco Cisternino
> Cc: petsc-users
> Oggetto: Re: [petsc-users] AMG Variable block preconditioner
>
> Marco,
>
> you should define what do you mean by "AMG block preconditioning";
> separate AMG on each block? What operator do you plan to precondition?
> AFAIK, MatSetVariableBlockSizes is just exploited by the Jacobi solver .
>
> Thanks
> Stefano
>
> Il giorno lun 28 ott 2019 alle ore 19:05 Marco Cisternino via petsc-users <
> petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>> ha scritto:
> Hello everybody.
> We would like to setup an algebraic multi-grid block preconditioner and I
> would like to be able to define custom blocks of variable sizes. Reading
> the documentation, it seems that this can be achieved using the "PCGAMG"
> preconditioner and defining the blocks with the function
> "MatSetVariableBlockSizes". Is this correct?
> Are the variable blocks exploited by PCGAMG algorithms? We suppose this PC
> structure is already exploited in PCVPBJACOBI.
> Are the different options like PCHYPRE (setting "-pc_hypre_type" to
> "boomeramg") suitable for AMG preconditioner with variable size blocks?
> If none of the above solutions are available, could anyone suggest any
> other strategy in order to get a preconditioner like this using PETSc?
> Any help is much appreciated.
> Thanks.
>
> Best regards,
>
> Marco Cisternino
>
>
> --
> Stefano
>


-- 
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20191028/fa1834c0/attachment.html>