Re: [Getfem-users] High level generic assembly procedures

[Yves Renard]

Dear Marco,

Concerning your question on Grad_u for a vector field, it is usually an
order two  tensor (a matrix) except in 1D.
I tried to to the best to make the most operations "dimension
indepedent" so there is some permitivity in the langage (components of
size 1 are sometimes ignored).
Remember also that you can have the expression of any term with the
commant Print. For instance "Print( Grad_u).Test_p" will print the
gradient of u on each Gauss point. It does a lot of print, but at least,
you can see the format of the term.

Yves.


Le 02/04/2014 17:21, Marco Pischedda a écrit :
> Hi,
>
> I have other questions:
>
> - I tried to assemble separately the following terms:
>   "Grad_u.Test_p" , "p.Grad_Test_u", "p.Test_u" and the code works correctly.
>   Then I want to assemble the sum of this terms, i.e: "Grad_u.Test_p +
> p.Grad_Test_u+p.Test_u"
>   but I receive the following error:
>
>    Addition or substraction of incompatible expressions or of different sizes
>    terminate called after throwing an instance of 'gmm::gmm_error'
>    what():  Error in getfem_generic_assembly.cc, line 3591 :
>    Error in assembly string
>    Aborted
>
> - I'm working in 1d problem with vectors as unknowns. Grad_u is
> therefore a vector or is a        tensor? When I do Grad_u.Test_p the
> result is a scalar or a vector? Test_p is a vector or a scalar?
>
> Thanks in Advance
>
> Marco
>
>
>
> 2014-04-01 17:51 GMT+02:00 Marco Pischedda <address@hidden>:
>> Ok thank you,
>>
>> I tried it and it works. I will let you know if there are other problems.
>>
>> Thanks
>>
>> Marco
>>
>> 2014-04-01 17:16 GMT+02:00 Yves Renard <address@hidden>:
>>> Dear Marco,
>>>
>>> All seems to me correct in your implementation. This is probably just
>>> the test line 2074 of getfem_generic_assembly.cc
>>> which is not correct for one-dimensionnal problems.
>>>
>>> I think the test should be
>>>
>>>  GA_DEBUG_ASSERT((qdim == 1 && t.sizes()[0] == N) ||
>>>                       (t.sizes()[1] == N && t.sizes()[0] == qdim) ||
>>>                       (N == 1 && t.sizes()[0] == qdim),
>>>                       "dimensions mismatch");
>>>
>>> May be you can try this. I will validate it if it works.
>>>
>>> Regards,
>>>
>>> Yves.
>>>
>>>
>>>
>>> Le 01/04/2014 16:56, Marco Pischedda a écrit :
>>>> Dear Yves,
>>>>
>>>> thank you for your fast answer.
>>>>
>>>> I have another question:
>>>>
>>>> - I have a monodimensional problem but the unknowns are vectorial. I
>>>> set the vectorial
>>>> dimension of the unknows with mf_u.set_qdim(3) and with mf_p.set_qdim(3).
>>>> When I define the expression " Grad_u.Test_p "  i receive the following 
>>>> error:
>>>>
>>>> terminate called after throwing an instance of 'gmm::gmm_error'
>>>>   what():  Error in
>>>> ../../getfem-svn/getfem/src/getfem_generic_assembly.cc, line 2074 :
>>>> dimensions mismatch
>>>>
>>>> Grad_u should be a 2nd order tensor, while Test_p should be a vector.
>>>> I suppose the
>>>> problem is that Grad_u is interpreted as a vector while Test_p is
>>>> interpreted as a scalar.
>>>> How can I use the high level generic assembly procedures on vectorial 
>>>> problems
>>>> defined on a monodimensional computational domain?
>>>>
>>>> Thanks in advance
>>>>
>>>> Marco
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> 2014-04-01 8:42 GMT+02:00 Yves Renard <address@hidden>:
>>>>> Dear Marco,
>>>>>
>>>>> Yes, your code is correct and it should work correctly.
>>>>> Note that you can also use the high level generic assembly with the
>>>>> model object using a generic assembly brick.
>>>>> Note also that high level assembly is only available in the svn
>>>>> repository version of Getfem
>>>>> (and a very recent version, at least r4570 because a bug have been
>>>>> corrected on coupled problems recently).
>>>>>
>>>>> Yves.
>>>>>
>>>>>
>>>>> Le 31/03/2014 14:00, Marco Pischedda a écrit :
>>>>>> Dear all,
>>>>>>
>>>>>> I want to use the high level generic assembly procedures in order to
>>>>>> use the automatic differentation for calculating the Jacobian of a
>>>>>> non-linear problem.
>>>>>>
>>>>>> For example I want to calculate the Jacobian of two vectorial
>>>>>> equations in the unknowns "u" and "p". The first vectorial equation is
>>>>>> (u+p).Test_u while the second is (u+p).Test_p.
>>>>>>
>>>>>>  It is correct the following code?
>>>>>>
>>>>>>  gmm::sub_interval Iu(0, ndofs_u);
>>>>>>  gmm::sub_interval Ip(ndofs_u,ndofs_p);
>>>>>>  workspace.add_fem_variable("u", mf_u, Iu, U);
>>>>>>  workspace.add_fem_variable("p", mf_p, Ip, P);
>>>>>>  workspace.add_expression("(u+p).Test_u + (u+p).Test_p",mim);
>>>>>>  getfem::model_real_sparse_matrix Jac(ndofs_u+ndofs_p, ndofs_u+ndofs_p);
>>>>>>  workspace.set_assembled_matrix(Jac);
>>>>>>  workspace.assembly(2);
>>>>>>
>>>>>> In the matrix Jac I have the Jacobian of the system?
>>>>>>
>>>>>>
>>>>>> Thanks in advance
>>>>>>
>>>>>> Marco
>>>>>>
>>>>>> _______________________________________________
>>>>>> 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
>>>
>>> ---------
>>>


-- 

  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

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