[petsc-dev] Adjacency relations in Sieve and stencils

[Jed Brown]

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).


>
> 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
>
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