[petsc-users] DMPlex with spring elements

[Miguel Angel Salazar de Troya]

> If you need a symmetric Jacobian, you can use the BC facility in
> PetscSection, which eliminates the
> variables completely. This is how the FEM examples, like ex12, work.

Would that be with PetscSectionSetConstraintDof ? For that I will need the
PetscSection, DofSection, within DMNetwork, how can I obtain it? I could
cast it to DM_Network from the dm, networkdm,  declared in the main
program, maybe something like this:

DM_Network     *network = (DM_Network*) networkdm->data;

Then I would loop over the vertices and call
PetscSectionSetConstraintDof if it's a boundary node (by checking the
corresponding component)

Thanks for your responses.

Miguel



On Thu, Sep 25, 2014 at 2:42 PM, Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
>
> > On Thu, Sep 25, 2014 at 1:46 PM, Abhyankar, Shrirang G. <
> abhyshr at mcs.anl.gov
> >> wrote:
> >
> >> You are right. The Jacobian for the power grid application is indeed
> >> non-symmetric. Is that a problem for your application?
> >>
> >
> > If you need a symmetric Jacobian, you can use the BC facility in
> > PetscSection, which eliminates the
> > variables completely. This is how the FEM examples, like ex12, work.
>
> You can also use MatZeroRowsColumns() or do the equivalent
> transformation during assembly (my preference).
>



-- 
*Miguel Angel Salazar de Troya*
Graduate Research Assistant
Department of Mechanical Science and Engineering
University of Illinois at Urbana-Champaign
(217) 550-2360
salaza11 at illinois.edu
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