Re: [Getfem-users] new_interpolated_fem problem

[Yves Renard]

Le Mercredi 28 Février 2007 14:20, Andriy Andreykiv a écrit :
> Good day gentlemen,
>
>       I'm having problems with interpolating a finite element method from one
> mesh to the other (getfem::new_interpolated_fem). What I want to do is the
> following, below there is a code that first defines two quad elements (in
> 2D space) and a line elemnet that crosses it arbitrarily in the middle
> (there is a picture bellow). I want to calculate a mass matrix (used for
> fictitious domain method) which is evaluated on that segment  element, but
> in fact is calculated as a product of shape functions from the quads and
> the segment element (and the integration is over the segment):
>
> M=\int_{segment} Base(the setment) X Base(the quads) dx
>
> I'm getting an error:
>
> interpolated_fem::update from context : convex_index = [0]
> ============================================
>
> |      An error has been detected !!!      |
>
> ============================================
> Error in ./gmm_opt.h, line 76 :
> non invertible matrix
>
> I would really appreciate the help.
> Best regards,
>                       Andriy


Hi Andriy,

I see two errors in your program.
The addition of the two quad element in the mesh should be writen:

     ind1[0]=quad_mesh.add_point(bgeot::base_node(0.0,0.0));
     ind1[1]=quad_mesh.add_point(bgeot::base_node(1.0,0.0)); 
     ind1[2]=quad_mesh.add_point(bgeot::base_node(0.0,1.0));
     ind1[3]=quad_mesh.add_point(bgeot::base_node(1.0,1.0));
     ind2[0]=ind1[1];
     ind2[1]=quad_mesh.add_point(bgeot::base_node(2.0,0.0));
     ind2[2]=ind1[3];
     ind2[3]=quad_mesh.add_point(bgeot::base_node(2.0,1.0)); 
     ind3[0]=line_mesh.add_point(bgeot::base_node(0.5,0.5));
     ind3[1]=line_mesh.add_point(bgeot::base_node(1.5,0.5));
     quad_mesh.add_parallelepiped(2,ind1.begin());
     quad_mesh.add_parallelepiped(2,ind2.begin());

this particular numeration of the vertex come from the fact that 
quadrilaterons are defined as tensorial product of two segments in Getfem.

Also, th line
getfem::mesh_fem mq_interpolate(mq.linked_mesh());

should be replaced by
getfem::mesh_fem mq_interpolate(ml.linked_mesh());

With this modifications, the program seems to  work !

Best regards,

Yves.

-------------------------------------------------------------------------
  Yves Renard (address@hidden)       tel : (33) 04.72.43.80.11
  Pole de Mathematiques, INSA de Lyon          fax : (33) 04.72.43.85.29
  Institut Camille Jordan - CNRS UMR 5208
  20, rue Albert Einstein
  69621 Villeurbanne Cedex, FRANCE
  http://math.univ-lyon1.fr/~renard
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