Re: [Getfem-users] Bug? in enumerating DOFs on region and faces

[Yves Renard]

Dear Roman,

The policy for which a dof is on a face or not is rather clear : A dof should 
be declared on a face if the corresponding shape function is nonzero on that 
face. 
Surprisingly, the belonging on faces of the derivative dof of the segment 
hermite element was explicitely disabled (getfem_fem.cc lines 1471 and 1477). 
This was not correct, of course and I don't remember why it is so !

Thank you for this bug report !

Yves.


On vendredi 16 juillet 2010, Roman Putanowicz wrote:
> Dear Yves,
> 
> I think I have found a bug in accessing DOFs on regions and faces.
> 
> The setup is as follows : single segment mesh with HERMITE fem.
> I create two mesh regions (for the left end node and for the right end
> node).
> 
> The output of the demo program (sent in attachment) is as follows:
> 
> -----------------------------------
> $ ./dofs_of_region
> DOFs on the left end : [0]
> DOFs on the right end : [2]
> DOFs on convex : 0 1 2 3
> DOFs on face 0 of convex : 2
> DOFs on face 1 of convex 0
> -----------------------------------
> 
> DOFs on convex are listed properly as 0 1 2 3.
> I would expect DOFs on left end region as well as dofs on face 1 of the
> convex to be [0,1] and not just [0]. So it seems that the dofs for
> derivative degrees of freedom are missing.
> 
> I have looked at code for dal::bit_vector mesh_fem::basic_dof_on_region()
> but I do not see there provision for non-Lagrangian elements.
> 
> I can check if the fem of a convex is Lagrangian but what should be done
> if it is not?
> 
> I am afraid that this can be a little pandora box :( but hope that this is
> not) (in particular I have in mind the code for setting Dirichlet boundary
> condition on Hermite elements).
> 
> In attachment there is mentioned test code to reproduce the bug.
> 
> Regards
> 
> Roman


-- 

  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
  Pole de Mathematiques, INSA-Lyon             fax : (33) 04.72.43.85.29
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  http://math.univ-lyon1.fr/~renard

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