[petsc-users] Distributing data along with DMPlex

[Alejandro D Otero]

Thanks,
The problem then is that after DMPlexDistribute the DMPlex 'points' are
renumbered. So if the values are related to each point in the original
numbering how do I set the values after the distribution. I know the
property stored in the vector related to the entities with the numbering of
the original mesh which I use to create the first DMPlex.

Ideally for me, I would like to set the values in the vector before
DMPlexDistribute and get the vector components renumbered and redistributed
accordingly in a global vector. And then, get the local vector.

Hope it could be more clear now.
Regards,

Alejandro



On Wed, Dec 16, 2015 at 7:01 PM, Justin Chang <jychang48 at gmail.com> wrote:

> I think you would follow this order:
>
> 1*) create a DMPlex (depth, chart, etc) on rank 0. Other ranks have an
> empty DM
>
> 2) DMPlexDistribute()
>
> 3*) Create the PetscSection
>
> 4) DMCreateGlobalVector()
>
> 5) DMCreateLocalVector()
>
> Now you have a global vector and a local vector for your distributed
> DMPlex. The mapping/ghosting/etc of dofs is already taken care of.
>
> * if you're using standard Galerkin FE then in SNES examples 12 and 62
> (and maybe others?) the first step is handled through the mesh generation
> functions and step 3 is handled through step 4
>
> Thanks,
> Justin
>
> On Wednesday, December 16, 2015, Alejandro D Otero <aotero at fi.uba.ar>
> wrote:
>
>> Hi, I need some help understanding how to distribute data together with a
>> dmplex representing a FE mesh.
>> At the beginning I define the structure of the dmplex assigning certain
>> number of DoF to cells, edges and vertexes, in one process (the dmplex in
>> the rest is empty)
>> I create a petscsecton and I create an associated global vector with the
>> quantities I want to store.
>> Then I distribute the dmplex over all the processes.
>> * Although this does not perform well it is just a starting point. I know
>> it has to be improved.
>>
>> I would like to have the global vector distributed accordingly so that
>> each process has access to the corresponding local part with its DoF
>> (possibly adding some ghost values corresponding to the shared DoF not
>> taken care by it).
>>
>> Is there any 'correct' way to do that in PETSc?
>>
>> Thanks in advance,
>>
>> Alejandro
>>
>
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