[petsc-users] DMPlexCreateFromCellList and hybrid meshes

[Matthew Knepley]

On Fri, Jan 3, 2014 at 10:30 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Fri, Jan 3, 2014 at 9:57 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>
>> Cedric Doucet <cedric.doucet at inria.fr> writes:
>>
>> > I could use DMPlexCreateFromDAG but there are several drawbacks:
>> > 1. DMPlexCreateFromDAG is not well documented;
>> > 2. other developers will have to understand a tricky data structure
>> > (DAG) to modify my code (see point 1 to understand why it is a
>> > problem);;
>>
>> Every public function is supposed to have a man page.  Matt neglected
>> this rule in DMPlexCreateFromDAG and it's perfectly valid to complain
>> about that.  However, I think DMPlexCreateFromDAG provides the
>> functionality you need, and is sufficiently general to deal with things
>> like boundary faces which are needed for most real simulations.
>>
>> > 3. DMPlexCreateFromDAG looks like a low-level function in comparison
>> > with DMPlexCreateFromCellList which acts at a higher level: if you
>> > modify this structure, I or someone else will have to modify my code
>> > (see point 2 to understand why it is a problem);
>>
>> It only uses complicated words; the data structure is basically the same
>> as what you're asking for, with the added flexibility of being able to
>> represent meshes containing cells with more than one topological
>> dimension (e.g., volumes and faces).
>>
>> > You proposed to modify DMPlexCreateFromCellList function for me and I
>> > decided to accept it after thinking about it.  Did you change your
>> > mind?
>>
>> I didn't propose that.  Maybe Matt did and of course he's welcome to
>> generalize the function.
>>
>
> DMPlexCreateFromDAG() is exactly that generalization. What is different
> from
> CreateFrmCellList()?
>

I'm sorry, I am sick today. Here is a fuller explanation. A 1-level DAG is
exactly the same
as the cell-vertex input for CellList() EXCEPT that all numbering is
contiguous. I also added
a gmsh reader, although it is not fully functional. He could not have
chosen a worse format
for preallocating, and the boundary handling is insane, so I am delaying
writing the full thing.
I am so disappointed with the gmsh format, I am not anxious to work with
anything they do.

    Matt


>    Matt
>
>
> --
> 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
>



-- 
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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