[petsc-users] DMPlex with spring elements

[Matthew Knepley]

On Fri, Sep 26, 2014 at 10:26 AM, Miguel Angel Salazar de Troya <
salazardetroya at gmail.com> wrote:

> Yeah, but doesn't it only work with the local vectors localX and localF?
>

I am telling you what the interface for the functions is. You can do
whatever you want inside.

  Matt


> Miguel
>
> On Fri, Sep 26, 2014 at 10:10 AM, Matthew Knepley <knepley at gmail.com>
> wrote:
>
>> On Fri, Sep 26, 2014 at 10:06 AM, Miguel Angel Salazar de Troya <
>> salazardetroya at gmail.com> wrote:
>>
>>> That means that if we call SNESSetFunction() we don't build the
>>> residual vector in parallel? In the pflow example (
>>> http://www.mcs.anl.gov/petsc/petsc-as/petsc-current/src/snes/examples/tutorials/network/pflow/pf.c.html)
>>> the function FormFunction() (Input for SNESSetFunction() works with the
>>> local vectors. I don't understand this.
>>>
>>
>> FormFunction() in that link clearly takes in a global vector X and
>> returns a global vector F. Inside, it
>> converts them to local vectors. This is exactly what you would do for a
>> function given to SNESSetFunction().
>>
>>   Matt
>>
>>
>>>
>>> Thanks
>>> Miguel
>>>
>>> On Fri, Sep 26, 2014 at 9:34 AM, Matthew Knepley <knepley at gmail.com>
>>> wrote:
>>>
>>>> On Fri, Sep 26, 2014 at 9:31 AM, Miguel Angel Salazar de Troya <
>>>> salazardetroya at gmail.com> wrote:
>>>>
>>>>> 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
>>>>>
>>>>
>>>> SNESSetFunction() expects the user to construct the entire parallel
>>>> residual vector. DMSNESSetFunctionLocal()
>>>> expects the user to construct the local pieces of the residual, and
>>>> then it automatically calls DMLocalToGlobal()
>>>> to assembly the full residual. It also converts the input from global
>>>> vectors to local vectors, and in the case of
>>>> DMDA multidimensional arrays.
>>>>
>>>>   Thanks,
>>>>
>>>>     Matt
>>>>
>>>>
>>>>> 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
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> 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
>>>
>>>
>>
>>
>> --
>> 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
>
>


-- 
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
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