[petsc-dev] questions on new include organization

[Barry Smith]

On Feb 12, 2013, at 11:24 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> 
> On Tue, Feb 12, 2013 at 11:17 PM, Matthew Knepley <knepley at gmail.com> wrote:
> Yes. PetscSection represents groups of numbers, and you can see the grouping.
> 
> IS is a map from (int) -> (int), but PetscSection is a map from (int) -> (int,int) where the pair is interpreted to mean an interval of non-negative extent. If it's any use, an IS could be thought of as the special case (int) -> (int,1).

   Is it? Maybe a more general definition of PetscSection would be better as map from (int) -> IS   Matt's current usage is very restricted to only contiguous blocks of elements in a group. Need that be it? Should that be it? 

   Barry

>  
>  
>    What queries "do not just return members of this list" in PETSc section? (That is queries we wish to retain anyways).
> 
> For example, you can ask "how many items are in group p?". This is crucial, and the whole point of the structure.
> I don't see how you can recover that information from just the list of dof numbers.
> 
>