[petsc-users] DMPlex with spring elements

[Miguel Angel Salazar de Troya]

Thanks. I had another question about the DM and SNES and TS. There are
similar routines to assign the residual and jacobian evaluation to both
objects. For the SNES case are:

DMSNESSetFunctionLocal
DMSNESSetJacobianLocal

What are the differences of these with:

SNESSetFunction
SNESSetJacobian

and when should we use each? With "Local", it is meant to evaluate the
function/jacobian for the elements in the local processor? I could get the
local edges in DMNetwork by calling DMNetworkGetEdgeRange?

Miguel

On Thu, Sep 25, 2014 at 5:17 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Sep 25, 2014 at 5:15 PM, Miguel Angel Salazar de Troya <
> salazardetroya at gmail.com> wrote:
>
>> > 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)
>>
>> I admit to not completely understanding DMNetwork. However, it eventually
> builds a PetscSection for data layout, which
> you could get from DMGetDefaultSection(). The right thing to do is find
> where it builds the Section, and put in your BC
> there, but that sounds like it would entail coding.
>
>   Thanks,
>
>      Matt
>
>
>> 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
>>
>>
>
>
> --
> 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
>



-- 
*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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