[petsc-dev] Adjacency relations in Sieve and stencils

[Matthew Knepley]

On Thu, Aug 23, 2012 at 5:59 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Thu, Aug 23, 2012 at 5:50 PM, Chris Eldred <chris.eldred at gmail.com>wrote:
>
>> For the extended operators, I was going to write:
>>
>> 1) DMComplexGetLabelClosure- returns the points from a transitive
>> closure with a given value for a given label (this will implement both
>> star(vertex) \ support(vertex) and closure(cell) \ cone(cell); along
>> with many other operators)
>> 2) DMComplexGetNeighbors- returns U cone(support()) OR  U
>> support(cone()) by setting a Boolean flag
>>
>> These two operators should cover "nearest neighbors" of all types.
>>
>
> What about having
>
> typedef enum {DMCOMPLEX_VERTEX = 0x1,DMCOMPLEX_EDGE = 0x2,DMCOMPLEX_FACE =
> 0x4,DMCOMPLEX_CELL = 0x8} DMComplexPointType;
>
> DMComplexGetClosure(dm,point_type,label,array,basepoint,&npoints,&values)
>
> You can always use point_type = my_type-1 to get values from all points in
> the closure, but this allows you to jump directly to particular levels.
> Similar for Support. Then you could get rid of cone and star because nobody
> can remember those anyway. You just have Closure and Support with results
> restricted to points of a given type (topological dimension).
>

Never.

   Matt


>
>> On Thu, Aug 23, 2012 at 12:39 PM, Chris Eldred <chris.eldred at gmail.com>
>> wrote:
>> > Sounds good- I will write the extended topological operators (
>> > star(vertex) \ support(vertex) ; closure(cell) \ cone(cell) and U
>> > cone(support(edge)) ) and let you know if I have questions/run into
>> > issues!
>> >
>> > -Chris
>> >
>> > On Thu, Aug 23, 2012 at 12:22 PM, Matthew Knepley <knepley at gmail.com>
>> wrote:
>> >> On Thu, Aug 23, 2012 at 12:19 PM, Chris Eldred <chris.eldred at gmail.com
>> >
>> >> wrote:
>> >>>
>> >>> I am working with a 2D unstructured mesh using sieve and I wanted to
>> >>> get some advice on how to determine adjacency relations using the
>> >>> topological operators provided by Sieve (cone, support, closure,
>> >>> star). I have figured out the following:
>> >>>
>> >>> Vertices for a given edge: cone(edge)
>> >>> Cells for a given edge: support(edge)
>> >>>
>> >>> Cells for a given vertex: star(vertex) \ support(vertex)
>> >>> Edges for a given vertex: support(vertex)
>> >>>
>> >>> Edges for a given cell: cone(cell)
>> >>> Vertices for a given cell: closure(cell) \ cone(cell)
>> >>>
>> >>> The set of edges associated with the cells for a given edge: U
>> >>> cone(support(edge)) - ie the union of the cones of the support of the
>> >>> edge
>> >>>
>> >>> Are there other topological operators that more naturally express
>> >>> these relations (especially the ones involving unions or complements)?
>> >>
>> >>
>> >> The only other builtin operations are meet and join. You are correct
>> that
>> >> you
>> >> want to use union there. We could add routines like
>> >>
>> >>   DMComplexGetConeUnion(dm, [p], &unionSize, &unionArray);
>> >>
>> >> but it was not clear that would do anything other than bloat the
>> interface.
>> >> I
>> >> think the best way to procede is to write these convenience routines
>> using
>> >> the lower level primitives, and move them into PETSc if they turn out
>> to be
>> >> useful. I can help you write them.
>> >>
>> >>    Matt
>> >>
>> >>>
>> >>>
>> >>> --
>> >>> 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
>>
>>
>>
>> --
>> 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
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