[petsc-dev] Best Way to Assign Cell Number to VTK Plot in DMPlex

[Matthew Knepley]

On Fri, Oct 4, 2019 at 7:46 PM Faibussowitsch, Jacob <
jfaibussowitsch at anl.gov> wrote:

> If you are requesting a Vec from a Plex, then the discretization in its DS
> determines its size.
>
> What if I have multiple fields on a single DM with varying numComponents
> per field (although each one has the same quadrature number and dimension I
> believe)? Does it just make the vec based on field 0?
>

No, the Vec holds everything in the DS.

  Thanks,

     Matt


> I have made a PetscFE,  and used it to set each field, then called
> DMCreateDS on the dm afterwards.
>
> Best,
>
> Jacob
>
> On Oct 4, 2019, at 4:59 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
> On Fri, Oct 4, 2019 at 3:09 PM Faibussowitsch, Jacob <
> jfaibussowitsch at anl.gov> wrote:
>
>> Note that Paraview already knows the cell number and can display it
>>
>> Now that would have been useful to know months ago.
>>
>> Here is me making a similar field containing the rank instead of the cell
>> number:
>>
>> Yes I ended up cannibalizing that function and this worked well enough.
>> One thing I noticed however is that it the global vector this creates is of
>> the size of number of cells, but when I create a global vector it is the
>> size of num vertices.
>>
>
> If you are requesting a Vec from a Plex, then the discretization in its DS
> determines its size. You need to
>
>   make a clone (DMClone) and set a P0 discretization
>
> This is what I do there.
>
>    Matt
>
>
>> I omitted the PETSc__rank_ options prefix part when creating the default
>> fe, is that responsible for setting the vec size here?
>>
>> Best,
>>
>> Jacob
>>
>> On Oct 4, 2019, at 9:42 AM, Matthew Knepley <knepley at gmail.com> wrote:
>>
>> On Thu, Oct 3, 2019 at 11:42 AM Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Tue, Oct 1, 2019 at 11:57 AM Faibussowitsch, Jacob via petsc-dev <
>>> petsc-dev at mcs.anl.gov> wrote:
>>>
>>>> Hello All,
>>>>
>>>> I am plotting an output value from a vecview, and want to show in a
>>>> separate plot which cells correspond to which values in the vec. I plan to
>>>> do this by making a field on the cells whose value is the global number of
>>>> that cell. I have 2 issues with this:
>>>>
>>>> 1. How do I guarantee that the ordering of the Vec I made corresponds
>>>> to the DMPlex cell ordering such that Vec(0) corresponds to Cells(0) etc.
>>>> (I make the Vec separately from the DM since using DMCreateLocalVector
>>>> makes a vector on the vertices)
>>>>
>>>> 2. I am trying to use DMPlexVTKWriteAll to make my output, so I am
>>>> adding my field to the DMPlexVTK using PetscViewerVTKAddField, but I can’t
>>>> seem to get PetscViewerVTKWriteFunction to work properly, and the man pages
>>>> don’t link to an example. Here is my code for this section:
>>>>
>>>> PetscErrorCode        (*PetscViewerVTKWriteFunction) (PetscObject,
>>>> PetscViewer);
>>>>
>>>> ierr = PetscViewerCreate(comm=PETSC_COMM_WORLD,
>>>> &vtkviewer);CHKERRQ(ierr);
>>>> ierr = PetscViewerVTKOpen(comm=PETSC_COMM_WORLD, "mesh.vtk",
>>>> FILE_MODE_WRITE, &vtkviewer);CHKERRQ(ierr);
>>>> ierr = PetscViewerSetUp(vtkviewer);CHKERRQ(ierr);
>>>>
>>>> PetscViewerVTKWriteFunction = (CellNum vtkviewer);
>>>>
>>>> ierr = PetscViewerVTKAddField(vtkviewer, (PetscObject) dm,
>>>> PetscViewerVTKWriteFunction, PETSC_VTK_CELL_FIELD, PETSC_TRUE,
>>>> CellNum);CHKERRQ(ierr);
>>>> ierr = DMPlexVTKWriteAll((PetscObject) dm, vtkviewer);CHKERRQ(ierr);
>>>>
>>>> Any help would be greatly appreciated!
>>>>
>>>
>>> I think what you want is to make a Section over cells with 1 dof, fill
>>> it with the cell number (from a global numbering), and then view that Vec.
>>>
>>
>> Here is me making a similar field containing the rank instead of the cell
>> number:
>>
>>
>> https://www.mcs.anl.gov/petsc/petsc-master/docs/manualpages/DMPLEX/DMPlexCreateRankField.html
>>
>> Note that Paraview already knows the cell number and can display it
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>>    Matt
>>>
>>>
>>>> Best,
>>>>
>>>> Jacob
>>>>
>>>>
>>>
>>> --
>>> 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/>
>>>
>>
>>
>> --
>> 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/>
>>
>>
>>
>
> --
> 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/>
>
>
>

-- 
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-dev/attachments/20191004/e0e67fa4/attachment.html>