[Dune] Features of Ghost-Elements

Martin Nolte nolte at mathematik.uni-freiburg.de
Sat Jun 11 20:20:39 CEST 2011


Hi Jö,

browsing through your feature list, I would expect ALU to support all of them
with a small exception: The same element might be represented by multiple copies
of the ghost if more than one face of the element touches a process border, one
copy for each face intersecting a process border. This is a tribute to the fact
that ALU does not natively support ghost elements. Apart from that, everything
should work as expected and you should file a bug report, if ALU fails to comply
with one of your assumptions.

Best,

Martin

On 06/11/2011 07:46 PM, Jö Fahlke wrote:
> Hi!
> 
> I'm trying to determine whether my method can do with ghosts instead of
> overlap, which brings me to the question what features are supported by
> ghosts.  Specifically I am interested in the support provided by UG<3>,
> ALUSimplex<3,3> and ALUCube<3,3>.
> 
> Features that are essential or very hard to avoid:
> 
>   1. For a ghost element e, gv.ibegin(e) and gv.iend(e) should iterate over
>      all intersections with interior elements.  Intersections with other
>      ghosts or the domain boundary may or may not be included, I don't care.
> 
>   2. For an interior element e, gv.ibegin(e) and gv.iend(e) should iterate
>      over all intersections which other interior elements, ghosts and the
>      domain boundary.
> 
>   3. For any ghost element e, gv.indexSet().index(e) must be a valid
>      expression and yield a correct index.
> 
>   4. For any intersection i, *i.inside() should always work and yield a valid
>      and correct element, even if that element is a ghost.
> 
>   5. For any intersection i except domain boundary intersections, *i.outside()
>      should always work and yield a valid and correct element, even if that
>      element is a ghost.
> 
>   6. For any intersection i, i.geometryInInside() should always work and yield
>      the expected geometry, even if the inside element is a ghost.
> 
>   7. For any intersection i except domain boundary intersections,
>      i.geometryInOutside() should always work and yield the expected geometry,
>      even if the outside element is a ghost.
> 
>   8. For any intersection i, i.geometry() should always work and yield the
>      expected geometry, even if the inside and/or the outside elements are
>      ghosts.
> 
> Features that are currently used but could possibly be avoided:
> 
>   9. For any ghost element e, e.type() must be a valid expression and yield
>      the correct GeometryType.
> 
> Features that would be good to have in the future but may be possible to
> avoid:
> 
>  10. For any ghost element e, e.geometry() must be a valid expression and
>      yield the expected geometry.
> 
> Thanks,
> Jö.
> 
> 
> 
> 
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-- 
Martin Nolte <nolte at mathematik.uni-freiburg.de>

Universität Freiburg                                   phone: +49-761-203-5642
Abteilung für angewandte Mathematik                    fax:   +49-761-203-5632
Hermann-Herder-Straße 10
79104 Freiburg, Germany



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