[petsc-dev] Ghost values in sieve

[Matthew Knepley]

On Thu, Aug 23, 2012 at 2:08 PM, Chris Eldred <chris.eldred at gmail.com>wrote:

> Awesome- that is easy. How do I access that SF?


I destroy it inside DMComplexPreallocateOperator(), but we can preserve it.

   Matt


> On Thu, Aug 23, 2012 at 12:54 PM, Matthew Knepley <knepley at gmail.com>
> wrote:
> > On Thu, Aug 23, 2012 at 1:42 PM, Chris Eldred <chris.eldred at gmail.com>
> > wrote:
> >>
> >> 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.
> >
> >
> > Okay, then for parallelism, I think you need nothing more than the SF we
> get
> > from Jacobian preallocation.
> >
> >   Thanks,
> >
> >      Matt
> >
> >>
> >> 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
> >
> >
> >
> >
> > --
> > 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
>



-- 
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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