[dune-fem] How to get DoFs for Dirichlet nodes with vector-valued unknowns

[Tobias Malkmus]

Hi Andrea

try this :

const SubEntityIteratorType endFaceIt = pointSet.template
endSubEntity<1>( localFaceNumber );
for( SubEntityIteratorType faceDofIt = pointSet.template
beginSubEntity<1>( localFaceNumber );
              faceDofIt != endFaceIt; ++faceDofIt )
{
   for( int i = 0; i < RangeType::dimension; ++i )
   {
       const int index = (*faceDofIt ) * RangeType::dimension + i;
       local[ index ] = ...
    }
}

where local is a local Lagrange discrete function.
In the same way you can modify the local stiffness matrix in the
index-th row/column.



Best Tobias


On 04/11/2013 07:12 PM, Sacconi, Andrea wrote:
> Hi all,
>
> I have a quick question for you.
>
> Suppose you need to find the global DoFs associated to the Dirichlet
> nodes. The purpose is, of course, to modify the rows of the stiffness
> matrix in the standard way, as well as the corresponding components on
> the rhs.
> When the unknown is a scalar variable, I don't have problems: I loop
> over the entities, extract the LagrangePointSetType set for each
> entity, use FaceDofIteratorType, ...
>
> But when the unknown is a vector-valued function, how do I proceed? I
> have tried to do exactly the same, and I noticed that the same node
> can refer to two different DoFs.
> The problem is, how do I prescribe the value for the function? Since
> it's a vector-valued function, where do I prescribe the first
> component and where the second?
> In other words, how is the DoFs set created?
>
> Thanks in advance for your help!
>
> Cheers,
> Andrea
>
>
> __________________________________________________________
>
> Andrea Sacconi
> PhD student, Applied Mathematics
> AMMP Section, Department of Mathematics, Imperial College London,
> London SW7 2AZ, UK
> a.sacconi11 at imperial.ac.uk
>
>
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> dune-fem at dune-project.org
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-- 
Tobias Malkmus                 <tomalk at mathematik.uni-freiburg.de>

Mathematisches Institut               Tel: +49 (0) 761 203 5651
Abt. für Angewandte Mathematik        Universität Freiburg
Hermann-Herder-Str. 10
79104 Freiburg
     

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