Re: [Getfem-users] Data for piecewise constant coefficients

[Jehanzeb Hameed]

I just did a test, and they seem to be equal.

-Jehanzeb

On Wed, Jul 8, 2009 at 1:29 PM, Jehanzeb Hameed<address@hidden> wrote:
> Dear Yves,
>
> I just started using getfem, so I am afraid my questions quite
> trivial. I wanted to ask/confirm a couple of more things:
>
>> mf.ind_dof_of_element(icv) gives the dof number of element icv
>
> I was wondering if the same thing can be achieved by another method.
> Since the subdomains are defined by mesh_regions, looking again at
> interpolation functions, they take in a mesh_region as argument. So,
> if I call interpolation_function multiple times (once  for each
> mesh_region) and pass in the same vector,  each interpolation_function
> will only fill in the part of the vector corresponding to its dof's.
> This way I should be able to get piecewise constant coefficients for
> each region. Is this correct?
>
> Thanks,
> -Jehanzeb
>
>
> On Wed, Jul 8, 2009 at 11:24 AM, Yves Renard<address@hidden> wrote:
>>
>> Dear Jehanzeb,
>>
>> This is the same of all finite element method. The function
>>
>> mf.ind_dof_of_element(icv)
>>
>> gives the dof number of element icv (a unique dof for the P0 method), and the
>> function
>>
>> mf.point_of_dof(idof)
>>
>> gives the coordinate of the finite element node. With this, is is not
>> difficult to fill the vector of dof (without any additional storage).
>>
>> Yves.
>>
>>
>>
>> On mercredi 8 juillet 2009, Jehanzeb Hameed wrote:
>>> Is there a simple way in getfem to map points to convexes, that is:
>>> > the interpolation point for each element is the barycenter. So you
>>> > can discriminate in wich part of your domain is the point.
>>>
>>> Given the particular barycenter, say 'b', do I have to build a list of
>>> all barycenters in the beginning, and then search for 'b' in that
>>> list? Or is there some already builtin way to go about it.
>>>
>>> Thanks,
>>> -Jehanzeb
>>>
>>> On Wed, Jul 8, 2009 at 4:50 AM, Yves Renard<address@hidden> wrote:
>>> > On mardi 7 juillet 2009, Jehanzeb Hameed wrote:
>>> >> Hello,
>>> >>
>>> >> In laplacian.cc  "getfem::classical_fem(pgt,0))" is used to represent
>>> >> the fem space for coefficient function (mf_coef). This coefficient
>>> >> function is constant on each convex. It is not used in laplacian.cc,
>>> >> and is set to one by creating a vector ones (
>>> >> std::vector<scalar_type>(mf_coef.nb_dof(), 1.0) ).
>>> >>
>>> >> Now say, I want to this coefficient to be piecewise constant, that is
>>> >> constant on each of (say two) subdomains. It seems I cant use
>>> >> interpolation for it, as interpolation functions use coordinates of
>>> >> points, and dont seem to indicate which convex they come from.
>>> >
>>> > Indeed you can. If you represent your coefficient on a P0 method
>>> > (piecewise constant), the interpolation point for each element is the
>>> > barycenter. So you can discriminate in wich part of your domain is the
>>> > point. If you want to fill the corresponding vector by hand, you can use
>>> > the method
>>> > mf.point_of_dof(i) for the P0 method which will give you the coordinates
>>> > of the corresponding barycenter. Otherwise, you can also use the
>>> > interpolation functions.
>>> >
>>> > Yves.
>>> >
>>> >> One way
>>> >> I can think of doing it, is to loop for mesh convexes, look up which
>>> >> region the convex belongs to, and then set the corresponding entry in
>>> >> the coefficient vector. However I am not sure if this is the way to
>>> >> go, as numbering of convexes in the mesh  may not correspond to
>>> >> numbering of dof's of the vector passed as data for assembly.
>>> >>
>>> >> Is the above method the one to use, or is there a more elegant way
>>> >> around this?
>>> >>
>>> >> Thanks,
>>> >> -Jehanzeb
>>> >>
>>> >> _______________________________________________
>>> >> Getfem-users mailing list
>>> >> address@hidden
>>> >> https://mail.gna.org/listinfo/getfem-users
>>> >
>>> > --
>>> >
>>> >  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
>>> >  Pole de Mathematiques, INSA-Lyon             fax : (33) 04.72.43.85.29
>>> >  20, rue Albert Einstein
>>> >  69621 Villeurbanne Cedex, FRANCE
>>> >  http://math.univ-lyon1.fr/~renard
>>> >
>>> > ---------
>>
>>
>>
>> --
>>
>>  Yves Renard (address@hidden)       tel : (33) 04.72.43.87.08
>>  Pole de Mathematiques, INSA-Lyon             fax : (33) 04.72.43.85.29
>>  20, rue Albert Einstein
>>  69621 Villeurbanne Cedex, FRANCE
>>  http://math.univ-lyon1.fr/~renard
>>
>> ---------
>>
>