Re: [Getfem-users] write on global matrix with gmm

[Yves Renard]

On Monday 19 November 2007 11:15, mikael gueguen wrote:
> hi
> what is the good way to write global matrix for FEM with gmm?
> if i use a dense_matrix for writing the global matrix during the
> assembly procedure, i have problem with large scale problem,
> and if i use a col_matrix < gmm::wsvector<double> >, it 's not
> possible to access the rows, and i cannot insert boundary condition.
>
> How can i resolve that?
>

You mean you want to prescribe Dirichlet type boundary conditions (solution 
prescribed on the boundary) ?
It depends on how you prescribe the boundary conditions. There is at least 
three possibilities : Adapt the stiffness matrix cleaning some lines of the 
matrix, penalization or Lagrange multipliers.
For the first method, the optimal way if either to have a row matrix 
(row_matrix < gmm::wsvector<double> > or row_matrix < gmm::rsvector<double> > 
for instance) or if you have a column matrix, set to zero the potentialy non 
zero elements by considering the neighbor dofs (i.e. the dofs of the elements 
containing the dof to be prescribed).

Yves.


-- 

  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
  Pole de Mathematiques, INSA de Lyon          fax : (33) 04.72.43.85.29
  20, rue Albert Einstein
  69621 Villeurbanne Cedex, FRANCE
  http://math.univ-lyon1.fr/~renard

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