Re: [Getfem-users] bilaplacian

[Jano]

Hi Yves,

Yes I did try IM_GAUSS1D(5) with no success.

When I use " add_normal_derivative_Dirichlet_condition_with_multipliers
" I get " sub matrix too large ",

I made some test with the bilaplacian.cc example, the 1d case seams to
have some problem I'm not sure but looks like a bug.
The 2d case looks ok, but I'm not sure about the analytical solution.
(The test I made was: bilaplacian(u) = const, u=0 and u'=0 in the borders)

any ideas?

Jano

On Sun, Sep 5, 2010 at 3:38 PM, Renard Yves <address@hidden> wrote:
>
>
> Dear Jano,
>
> IM_GAUSS1D(3) represent a (small) sub-integration. Did you try with
> IM_GAUSS1D(5) ?
>
>
> Yves.
>
>
>
>
> Jano <address@hidden> a écrit :
>
>> Hi,
>>
>> I just started using the getfem++ lib, made some tests but I'm getting
>> some weird results.
>> I wanted to test the equation:
>> d4u/dx4 = f
>> u = variable
>> f = constant = 2
>> b.c.
>>
>> u(0) = u(1) = 0
>> du(0) = du(1) = 0
>>
>> using FEM_HERMITE(1), simplex_geotrans(1,1) and IM_GAUSS1D(3),
>>
>> for what I know it is a well conditioned problem and should give the
>> exact solution.
>> It compiles, run, but give a huge condition number and nothing even
>> near the exact solution.
>>
>> thanks if anyone can help,
>> Jano
>>
>> ps: sorry if the email is duplicated
>>
>>
>> Here is my code if someone can find what i did wrong:
>>
>> #include <stdlib.h>
>> #include <string>
>> #include <getfem/getfem_mesh.h>
>> #include <getfem/getfem_mesh_fem.h>
>> #include <getfem/getfem_import.h>
>> #include <getfem/getfem_regular_meshes.h>
>> #include <getfem/getfem_mesh_im.h>
>> #include <getfem/getfem_models.h>
>> #include <gmm/gmm.h>
>> #include <getfem/getfem_export.h>
>> #include <getfem/getfem_model_solvers.h>
>> #include <getfem/getfem_fourth_order.h>
>>
>> bgeot::scalar_type condicaoDirichlet(const bgeot::base_node &x) {
>>    return 0.0;
>> }
>>
>> bgeot::scalar_type DcondicaoDirichlet(const bgeot::base_node &x) {
>>    return 0.0;
>> }
>>
>> bgeot::scalar_type D = 1.0;
>> bgeot::scalar_type f = -2.0;
>>
>>
>> /*
>>  *
>>  */
>> int main(int argc, char** argv) {
>>
>>    //FEM_HERMITE(n)-Elemento de Hermite com n dimensões.
>>    std::string femName = "FEM_HERMITE(1)";
>>    //Flag para a regiao de contorno
>>    int DIRICHLET_BOUNDARY_NUM = 0;
>>    //Malha
>>    getfem::mesh malha;
>>    //getfem::import_mesh(string FILENAME, string FORMAT, mesh m)
>>    //Geracao e refinamento da malha
>>    std::vector<getfem::size_type> nsubdiv(1);
>>    nsubdiv[0] = 50;
>>    //nsubdiv[1] = 100;
>>    getfem::regular_unit_mesh(malha, nsubdiv,
>> bgeot::simplex_geotrans(1,1));
>>    //mesh_fem representando U e f
>>    getfem::mesh_fem meshFem(malha);
>>    getfem::mesh_fem meshFemRightHandSide(malha);
>>    //Define o tipo de elemento finito
>>    meshFem.set_finite_element(getfem::fem_descriptor(femName));
>>
>>  meshFemRightHandSide.set_finite_element(getfem::fem_descriptor(femName));
>>    //IM_NC(n,k)-Integracao numerica com Newton-Cotes
>>    getfem::mesh_im meshIm(malha);
>>
>>  
>> meshIm.set_integration_method(getfem::int_method_descriptor("IM_GAUSS1D(3)"));
>>    //Instanciacao do modelo
>>    getfem::model modelo;
>>    //Atribui U e o metodo de integracao
>>    modelo.add_fem_variable("u", meshFem);
>>    //getfem::add_Laplacian_brick(modelo, meshIm, "u");
>>    modelo.add_initialized_scalar_data("D", D);
>>    getfem::add_bilaplacian_brick(modelo, meshIm, "u", "D");
>>    modelo.add_initialized_scalar_data("f", f);
>>    getfem::add_source_term_brick(modelo, meshIm, "u", "f");
>>    //Define a regiao de contorno com a flag DIRICHLET_BOUNDARY_NUM
>>    getfem::mesh_region border_faces;
>>    getfem::outer_faces_of_mesh(malha, border_faces);
>>    for (getfem::mr_visitor i(border_faces); !i.finished(); ++i) {
>>        malha.region(DIRICHLET_BOUNDARY_NUM).add(i.cv(), i.f());
>>    }
>>    //Condicoes de contorno de Dirichlet
>>    std::vector<bgeot::scalar_type> F(meshFemRightHandSide.nb_dof());
>>    std::vector<bgeot::scalar_type> F2(meshFemRightHandSide.nb_dof());
>>    getfem::interpolation_function(meshFemRightHandSide, F,
>> condicaoDirichlet);
>>    getfem::interpolation_function(meshFemRightHandSide, F2,
>> DcondicaoDirichlet);
>>    modelo.add_initialized_fem_data("DirichletData",
>>            meshFemRightHandSide, F);
>>    modelo.add_initialized_fem_data("derivadaDirichletData",
>>            meshFemRightHandSide, F2);
>>    getfem::add_Dirichlet_condition_with_multipliers(
>>        modelo, meshIm, "u", meshFem, DIRICHLET_BOUNDARY_NUM,
>> "DirichletData");
>>    getfem::add_normal_derivative_Dirichlet_condition_with_multipliers(
>>            modelo, meshIm, "u", meshFem, DIRICHLET_BOUNDARY_NUM,
>> "derivadaDirichletData");
>>
>>
>>    //Define o residuo maximo e um iterator
>>    bgeot::scalar_type maxResidualIterativeSolver = pow(10, -5);
>>     gmm::iteration iter(maxResidualIterativeSolver, 1, 40000);
>>    //Solver
>>    getfem::standard_solve(modelo, iter);
>>    //Guarda a solucao em u
>>    std::vector<bgeot::scalar_type> u = modelo.real_variable("u");
>>
>>    std::fstream solucao("solucao.txt",std::ios::out);
>>    for (unsigned i=0; i < gmm::vect_size(u); ++(++i))
>>        solucao << u[i] << "\t" << u[i+1] << "\n";
>>
>>    // when the 2nd arg is true, the mesh is saved with the |mf|
>>    meshFem.write_to_file("solucao.mf", true);
>>
>>
>>    //Exporta
>>    getfem::dx_export exp_dx("solucao.dx");
>>    exp_dx.exporting(malha);
>>    exp_dx.write_point_data(meshFem, u, "deslocamento");
>>
>>    getfem::vtk_export exp_vtk("solucao.vtk");
>>    exp_vtk.exporting(malha);
>>    exp_vtk.write_point_data(meshFem, u, "deslocamento");
>>
>>    return (EXIT_SUCCESS);
>> }
>>
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>>
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