[petsc-dev] PetscSection

[Matthew Knepley]

On Sat, Nov 10, 2012 at 2:16 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> On Sat, Nov 10, 2012 at 12:45 PM, Matthew Knepley <knepley at gmail.com> wrote:
>>
>> It just depends on what you want your assumptions to be. I am all for
>> experimenting. The
>> foregoing strategy is good because closure continues to work as
>> advertised, and all our
>> integration code is still dim-independent, but the assumption that
>> height 0 things are all
>> cells breaks down. This is not so bad, since we usually want to group
>> cells by material
>> anyway, using a Label, so I am fine with this.
>
>
> Okay, my complaint is that "stratum" is an additional concept that has no
> established use in the current lexicon and the generality of which doesn't
> really help the user because they have to do different things for codim 0
> and codim 1 anyway. If we are not causing extreme hardship or irreparably
> crippling the flexibility of their code, I think the interface should give
> access to by codim instead of by stratum.

I do not understand. Codim 0 and 1 are handled in an identical way.

I am not against some convenience interface for dim/co-dim, however it would
just be implemented by making a label, since we have many equivalent structural
things which would map to it.

   Matt

> Now in the P1 case, the faces do not store any data, therefore
> closure(some_cell) returns the same thing going directly to vertices as if
> the intermediate dimensions were populated. I think that by definition, this
> sort of mesh does not support getting faces of a cell, therefore it's
> correct to not store the cell -> boundary-face relation. The user can ask to
> interpolate the mesh if they want.
>
> I'm not sure about the multi-domain case where the user wants a high-order
> discretization in one domain and a P1 with non-interpolated mesh in another.
> The benefit of non-interpolated doesn't seem so clear in this case.



--
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