[Dune] Gridcheck asks for geometry.local() outside the element?

Jö Fahlke jorrit at jorrit.de
Thu Feb 26 17:25:16 CET 2015


Am Thu, 26. Feb 2015, 16:58:38 +0100 schrieb Aleksejs Fomins:
> I am now trying to make the gridcheck run with curvilinear grid.
> 
> It seems that at some point gridcheck calls the geometry.local() method for one of tetrahedra in the provided mesh. And it calls the method with a global coordinate that is clearly outside the element. I previously assumed this was an illegal action, so I throw an error there...
> 
> Questions:
> 1) Is this expected behaviour of gridcheck?
> 2) If yes, what is the expected return value?
> 3) If no, then the problem is elsewhere. To search for it, I need debug output. Does gridcheck have debug output and if yes how to switch it on?

Without having looked at what the grid check does: It is kind-of legal to
stuff a coordinate outside the element into local().  This can happen
e.g. during a hierarchic search, when you try to find the element that
contains a certain Coordinate.  You (as a grid implementor) can
however declare that this is not supported for your grid, as hierarchic search
is just a utility class.

Another instance where local() receives outside coordinates is due to rounding
errors.  You should allow that, but you can take advantage of the fact that
these coordinate will only be very slightly outside.

If you can smoothly extend the local() mapping to the outside of the element,
then you should return the result according to this smooth extension.
Otherwise you probably already have singularities on the boundary of the
element, and we have to think about that some more.

Regards,
Jö.

-- 
Jorrit (Jö) Fahlke, Institute for Computational und Applied Mathematics,
University of Münster, Orleans-Ring 10, D-48149 Münster
Tel: +49 251 83 35146 Fax: +49 251 83 32729

Das Erststudium soll bis zum berufsqualifizierenden Abschluss
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