[petsc-dev] PetscSection

[Jed Brown]

On Fri, Nov 9, 2012 at 7:58 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

> Just an implementation issue. To me the correct abstract model is "indices
> of an element" etc and whether this is done via a "closure" or listing them
> etc is just an implementation issue.
>

Right, I don't think it should be visible in the access interface whether
the implementation has built an Index (in the DB sense) providing the
closure directly or whether it's constructed on the fly from whatever
indirect information. There is a meaningful distinction between getting the
dofs associated with the element or face _interior_ versus its closure.


>    I realize this is different than Matt's abstract model. I am not saying
> my model is better than Matt's (from an abstract mathematicians Matt's is
> probably better) but I believe my model is much more sellable to the masses
> (remember very few abstract mathematicians use PETSc :-)).
>

Just a few months ago, you were arguing that (u,v) = \int u conj(v) since
that was the Math Convention and PETSc was for Mathematicians.


>    So we are set? We design and implement a better, more general IS
> concept?
>

I think so. I think Matt wants still to pull "fields" in, as well as
perhaps constraints (for BCs).

Now where do we put the convenience interface of accessing a chunk of data
in a Vec or array? Or does the new IS interface only give use the index
range associated with the block and we as the caller must do the indexing?
(I'm not opposed to the latter. It's slight clutter but removes more from
the inner loop.)
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