[petsc-dev] Adjacency relations in Sieve and stencils

[Chris Eldred]

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.

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