[Dune] parallel alugrid and p1operator

[Bernd Flemisch]

Dear Dune,

I run into some problems when trying to use ALUGrid with dune-disc's 
P1Operator in parallel. The assembly of the matrix fails, because it 
cannot get the correct global id of some of the ghost nodes. This is 
apparently due to the fact that the ghost nodes belonging to two ghost 
elements are doubled, and that p1operator fails with
Dune reported error: GridError: MatEntryExchange::gather(): index not in map

In the attached test case, a 2x2x1 grid is used. After the load balance 
step, each process has 4 elements (2 real plus 2 ghost), but 20 instead 
of 18 vertices (doubling the two ghost vertices belonging to both ghost 
elements).

I guess there is a reason that the ghost nodes are doubled. Can you 
explain it to me? Can you maybe give me some ideas on what I have to do 
to make p1operator work with a parallel unstructured grid?

Thank you very much. All the best
Bernd

-- 
_____________________________________________________________________

Bernd Flemisch                               phone: +49 711 685 69162
IWS, Universität Stuttgart                   fax:   +49 711 685 60430
Pfaffenwaldring 61                  email: bernd at iws.uni-stuttgart.de
D-70569 Stuttgart                       url: www.iws.uni-stuttgart.de
_____________________________________________________________________

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