Re: [Getfem-users] Example of a simple mixed-problem, or problem with two variables

[Jehanzeb Hameed]

Dear Renard,

I cant seem to find the function "gf_asm" to use in C++ code. I see it
in a .cc file in the source code for getfem, but there seems to be no
prototype for it in a header file.

Do you mean that I should use getfem::generic_assembly in the way you
have described?

Thanks,
-Jehanzeb

On Sun, Jul 5, 2009 at 3:39 PM, Renard Yves<address@hidden> wrote:
>
>
> Dear Jehanzeb,
>
> You have to use a volumic assembly . An example  for the matrix of the
> Laplace operator is
>
> gf_asm('volumic',['a=data(#2); ',...
>       'M(#1,#1)+=sym(comp(Grad(#1).Grad(#1).Base(#2))(:,i,:,i,j).a(j))'],
> mim, mf, mf_data, A);
>
> A matrix for a mixed term can be obtained in a same way with two mf :
>
>  gf_asm('volumic', 'M(#1,#1)+=comp(Grad(#1).Base(#2))(:,i,i,:)', mim, mf1,
> mf2);
>
> where mf1 should be a vectorial fem (for more details see the Getfem++
> documentation).
>
> Yves.
>
>
> Jehanzeb Hameed <address@hidden> a écrit :
>
>> I had a look at the Stokes example. It uses model bricks to form the
>> system. From the documentation, it seems using model bricks implicitly
>> chooses the bilinear variational form. I would like to define my own
>> bilinear form to form the matrix, in which I can define terms like
>> div(q) + c u  (q = vector, c = constant, u = another variable besides
>> q). How would I go about this?
>>
>> Thanks,
>> -Jehanzeb
>>
>> On Sun, Jul 5, 2009 at 11:05 AM, Iago Barbeiro<address@hidden>
>> wrote:
>>>
>>> Dear Jehanzeb,
>>>
>>> I think you may start by looking the Stokes example.
>>> It deals with two variables (û=uî+v^j and p) and has the term div(û).dp.
>>> Bon courage!
>>>
>>> Iago
>>>
>>> On Sun, Jul 5, 2009 at 6:07 AM, Jehanzeb Hameed <address@hidden>
>>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Is there a simple example in getfem where assembly is for two
>>>> variables? E.g. we may want to solve for "u" and "q" (with an equation
>>>> defining the relationship between u and q) . Such a case arises in
>>>> mixed methods.  Is there an example for mixed-poisson problem
>>>> somewhere? I know mixed-elasticity problem is given with getfem, but I
>>>> am not familiar with that particular problem.
>>>>
>>>> In particular, I am not sure how to refer to "q" and "u" in
>>>> generic_assembly routines. Say my weak form involves div(q) . v ? How
>>>> will I write this in "assem.set" routine? (I am guessing thats what I
>>>> am supposed to do).
>>>>
>>>> Thanks,
>>>> -Jehanzeb
>>>>
>>>> _______________________________________________
>>>> Getfem-users mailing list
>>>> address@hidden
>>>> https://mail.gna.org/listinfo/getfem-users
>>>
>>>
>>
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