[petsc-dev] PetscSection

[Jed Brown]

On Fri, Nov 9, 2012 at 8:34 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

> > I think so. I think Matt wants still to pull "fields" in, as well as
> perhaps constraints (for BCs).
>
>    He is wrong, that all belongs in DMs.
>

I agree, though it may be reasonable to return an IS describing one field,
then be able to get the closure with respect to that IS.


> >
> > 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.)
>
>    Accessing from an array? Maybe
>
>     Accessing from a vector? Unlikely since the destroys the hierarchy of
> IS below Vec. So that part may need to be in the Vec,  maybe
> VecGetSection(vec,index tag,is,&values)


Good, that also removes dependence on VecGetArray, which I hate.
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