[petsc-dev] Ghost values in sieve

[Chris Eldred]

I need the adjacency relations discussed in my other post- the only
one that is not part of closure(p) U star(p) is: U
cone(support(edge)). Given an edge p, I need all of the edges that
cover the same cell as edge p.

On Thu, Aug 23, 2012 at 12:17 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Thu, Aug 23, 2012 at 12:26 PM, Chris Eldred <chris.eldred at gmail.com>
> wrote:
>>
>> Yes- I am implementing the TriSK scheme
>> (www.mmm.ucar.edu/people/skamarock/Ringler_et_al_JCP_2009.pdf) on
>> arbitrary Voronoi meshes. In order to do wind/flux reconstruction at
>> the cell edges, it needs to know about the edges of adjacent cells-
>> which are outside of closure(p) U star(p).
>
>
> Great! Stuff that cannot be done with that structured crap. However, from
> quickly looking at
> the paper, there is nothing beyond the neighbors, so we can reuse the code
> from
> Jacobian preallocation. If you could tell me exactly what adjacency you
> need, we might be
> able to do it even more simply.
>
>    Matt
>
>>
>> On Thu, Aug 23, 2012 at 11:16 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>> > On Thu, Aug 23, 2012 at 12:12 PM, Chris Eldred <chris.eldred at gmail.com>
>> > wrote:
>> >>
>> >> Thanks- that helps a lot. If I need stencils that are larger than
>> >> closure(p) U star(p) (for a higher-order finite difference method, for
>> >> example), I assume that I need to create my own PetscSF's that
>> >> describe which points need to be ghosted?
>> >
>> >
>> > Is this still a fully unstructured method? The Sieve formalism doesn't
>> > give
>> > you a very efficient way to do this for structured or semi-structured
>> > grids.
>> >
>> > Even so, if wider stencils are to be supported, I think it should be
>> > implemented within the library. Doing it outside with the current
>> > infrastructure is going to be quite a rabbit hole.
>> >
>> >>
>> >> Is there some documentation or example code that explains the theory
>> >> behind star forests?
>> >
>> >
>> > Docs for the basic operations:
>> >
>> > http://59A2.org/files/StarForest.pdf
>>
>>
>>
>> --
>> Chris Eldred
>> DOE Computational Science Graduate Fellow
>> Graduate Student, Atmospheric Science, Colorado State University
>> B.S. Applied Computational Physics, Carnegie Mellon University, 2009
>> chris.eldred at gmail.com
>
>
>
>
> --
> 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



-- 
Chris Eldred
DOE Computational Science Graduate Fellow
Graduate Student, Atmospheric Science, Colorado State University
B.S. Applied Computational Physics, Carnegie Mellon University, 2009
chris.eldred at gmail.com