Re: [Getfem-users] Getfem-users Digest, Vol 116, Issue 6

[Sebastien . Court]

Hi Andrew,

I already had this error message, a long time ago. If I remember well,
this message can appear when the degree of the level-set is wrong, in view
of the way the level-set is defined and/or used. This degree must be 1
when it is a curve (in 2D), or 2 when it is a surface (in 3D):

getfem::level_set ls(mesh, degree = 1, with_secondary = false);

http://download.gna.org/getfem/html/homepage/userdoc/xfem.html

In your code, by default the degree of the level-set is equal to 1, and in
what follows it seems that we are in a 3D context.

Maybe the problem comes also from the fact that you may have to specify
secondary level-set functions. In that case your level-set object is not a
scalar-type anymore, but a vector.

Sincerely,

S.C



https://online.uni-graz.at/kfu_online/visitenkarte.show_vcard?pPersonenId=8E061E23CBE613F4&pPersonenGruppe=3




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> Today's Topics:
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>    1. Re: "level is zero!" (Andrew Roberts)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 14 Jun 2016 16:35:59 -0500
> From: Andrew Roberts <address@hidden>
> To: Yves Renard <address@hidden>
> Cc: address@hidden
> Subject: Re: [Getfem-users] "level is zero!"
> Message-ID:
>       <address@hidden>
> Content-Type: text/plain; charset="utf-8"
>
> Hello again,
>    I've been working diligently to understand as to why I receive "level
> is
> zero" error.  I'd appreciate any code review and advice.  The purpose is
> just to demonstrate basic xfem behavior in the compact specimen mesh
> (v4.gmsh.msh).
>
> Thank you,
> Andy
>
>
> /address@hidden compact.cc
>    @brief compact specimen problem.
>
> */
>
> #include "getfem/getfem_model_solvers.h"
> #include "getfem/getfem_export.h"
> #include "gmm/gmm.h"
> #include "getfem/getfem_import.h"
> #include "getfem/getfem_assembling.h"
> #include "getfem/getfem_generic_assembly.h"
> #include "getfem/getfem_mesh_im_level_set.h"
> #include "getfem/getfem_mesh_fem_level_set.h"
> #include "getfem/getfem_mesh_fem_product.h"
> #include "getfem/getfem_mesh_fem_global_function.h"
> #include "getfem/getfem_mesh_fem_sum.h"
> #include <string>
> #include <cstring>
> #include <sstream>
> #include <iostream>
>
> using std::endl; using std::cout; using std::cerr;
> using std::ends; using std::cin;
>
> using bgeot::size_type;
> using bgeot::base_node;
> using bgeot::base_small_vector;
> typedef getfem::model_real_plain_vector plain_vector;
>
>
> using bgeot::scalar_type; /* = double */
>
>
>
> int main(void) {
>
>
> double E = 21E6;     // Young Modulus (N/cm^2)
> double nu = 0.3;     // Poisson ratio
> double clambda = E*nu/((1+nu)*(1-2*nu));
> double cmu = E/(2*(1+nu));
> double clambdastar = 2*clambda*cmu/(clambda+2*cmu);
>
>
> double residual = 1E-9;
>
>
> getfem::mesh mesh;
> getfem::import_mesh("gmsh:v4.gmsh.msh",mesh);
>
>
> getfem::mesh_fem mf(mesh);
>
>
> getfem::level_set ls(mesh);
> getfem::mesh_level_set mls(mesh);
> mls.add_level_set(ls);
>
>
> std::vector<getfem::pglobal_function> vfunc(4);
>   for (unsigned j=0; j < 4; ++j) {
>     getfem::crack_singular_xy_function *s =
>       new getfem::crack_singular_xy_function(j);
>     vfunc[j] = getfem::global_function_on_level_set(ls, *s);
>   }
>
>
> getfem::mesh_fem_level_set mfls(mls, mf);
>
>
> getfem::mesh_fem_global_function mf_sing(mesh);
>
>
> mf_sing.set_functions(vfunc);
>
>
> getfem::mesh_fem_sum mfu(mesh);
>
>
> mfu.set_mesh_fems(mf_sing, mfls);
>
> getfem::mesh_im_level_set mim(mls,
> getfem::mesh_im_level_set::INTEGRATE_ALL,
> getfem::int_method_descriptor("IM_TETRAHEDRON(6)"),
> getfem::int_method_descriptor("IM_QUASI_POLAR(IM_TETRAHEDRON(8), 2)"));
>
>
> mls.adapt();
> mfls.adapt();
> mim.adapt();
>
>
> getfem::mesh_fem mfvm(mesh, 1);
>
> mfvm.set_classical_discontinuous_finite_element(1);
>
>
> getfem::model md;
> md.add_fem_variable("u", mfu);
>
>
> md.add_initialized_scalar_data("cmu", cmu);
> md.add_initialized_scalar_data("clambdastar", clambdastar);
>
>
> getfem::add_isotropic_linearized_elasticity_brick
>     (md, mim, "u", "clambdastar", "cmu");
>
>
>
> getfem::add_normal_Dirichlet_condition_with_multipliers(md,mim,"u", 1,
> 109);
>
> getfem::add_source_term_brick(md,mim,"u","[0,1640,0]", 108);
>
>
> gmm::iteration iter(residual, 1, 50);
> getfem::standard_solve(md, iter,
> getfem::rselect_linear_solver(md,"superlu"));
>
>
>
> plain_vector U(mfu.nb_dof()); gmm::copy(md.real_variable("u"), U);
> plain_vector VM(mfvm.nb_dof());
> getfem::compute_isotropic_linearized_Von_Mises_or_Tresca
>     (md, "u", "clamabdastar", "cmu", mfvm, VM, false);
>
>
> getfem::vtk_export exp2("d_w_vm.vtk", false);
> exp2.exporting(mfu);
> exp2.write_point_data(mfu, U, "displacement");
> exp2.write_point_data(mfvm, VM, "Von Mises stress");
>
>
> }
>
> On Mon, Jun 13, 2016 at 7:03 AM, Yves Renard <address@hidden>
> wrote:
>
>>
>> Dear Andrew,
>>
>> This message appear when the level_set function is identically zero on
>> an
>> element (the level set function have to be "close" to a signed
>> distance).
>> Are you sure you initialized your level-set function with a correct
>> value ?
>>
>> Best regards,
>>
>> Yves.
>>
>>
>> Le 12/06/2016 23:33, Andrew Roberts a écrit :
>>
>> Working to demo 3d XFEM crack propagation of a steel compact specimen
>> top-half (gmsh import).
>>
>> It compiles fine but the executable throws a "level is zero" error which
>> I'm uncertain of the source of this error.  Code attached below.
>>
>> /address@hidden compact.cc
>>>    @brief three-dimensional XFEM crack propagation.
>>>
>>> */
>>>
>>> #include "getfem/getfem_model_solvers.h"
>>> #include "getfem/getfem_export.h"
>>> #include "gmm/gmm.h"
>>> #include "getfem/getfem_import.h"
>>> #include "getfem/getfem_assembling.h"
>>> #include "getfem/getfem_generic_assembly.h"
>>> #include "getfem/getfem_mesh_im_level_set.h"
>>> #include "getfem/getfem_mesh_fem_level_set.h"
>>> #include "getfem/getfem_mesh_fem_product.h"
>>> #include "getfem/getfem_mesh_fem_global_function.h"
>>> #include "getfem/getfem_mesh_fem_sum.h"
>>> #include <string>
>>> #include <cstring>
>>> #include <sstream>
>>> #include <iostream>
>>>
>>> using std::endl; using std::cout; using std::cerr;
>>> using std::ends; using std::cin;
>>>
>>> using bgeot::size_type;
>>> using bgeot::base_node;
>>> using bgeot::base_small_vector;
>>> typedef getfem::model_real_plain_vector plain_vector;
>>>
>>>
>>> using bgeot::scalar_type; /* = double */
>>>
>>> int main(void) {
>>>
>>> double E = 21E6;     // Young Modulus (N/cm^2)
>>> double nu = 0.3;     // Poisson ratio
>>> double clambda = E*nu/((1+nu)*(1-2*nu));
>>> double cmu = E/(2*(1+nu));
>>> double clambdastar = 2*clambda*cmu/(clambda+2*cmu);
>>>
>>> double residual = 1E-9;
>>>
>>> getfem::mesh mesh;
>>> getfem::import_mesh("gmsh:v4.gmsh.msh",mesh);
>>>
>>>
>>> getfem::mesh_fem mf(mesh, 3);
>>>
>>> getfem::mesh_fem mfvm(mesh, 1);
>>>
>>> mf.set_finite_element(mesh.convex_index(),
>>> getfem::fem_descriptor("FEM_PK(3,2)"));
>>>
>>> mfvm.set_classical_discontinuous_finite_element(1);
>>>
>>> getfem::level_set ls(mesh, 1, true);
>>> getfem::mesh_level_set mls(mesh);
>>> mls.add_level_set(ls);
>>> mls.adapt();
>>>
>>> std::vector<getfem::pglobal_function> vfunc(6);
>>> for (unsigned i = 0; i < vfunc.size(); ++i){
>>>     getfem::abstract_xy_function *s =
>>>         new getfem::crack_singular_xy_function(i);
>>>     getfem::abstract_xy_function *c =
>>>         new getfem::cutoff_xy_function(0, .2,.01,.49);
>>>     s = new getfem::product_of_xy_functions(*s, *c);
>>>       vfunc[i] = getfem::global_function_on_level_set(ls, *s);
>>> }
>>>
>>> getfem::mesh_fem_level_set mfls(mls, mf);
>>>
>>> getfem::mesh_fem_global_function mf_sing(mesh,3);
>>>
>>> mf_sing.set_functions(vfunc);
>>>
>>> getfem::mesh_fem_product mf_asympt(mfls, mf_sing);
>>>
>>> getfem::mesh_fem_product mfu(mf_asympt);
>>>
>>> getfem::mesh_im_level_set mim(mls,
>>> getfem::mesh_im_level_set::INTEGRATE_ALL,
>>> getfem::int_method_descriptor("IM_TETRAHEDRON(6)"),
>>> getfem::int_method_descriptor("IM_QUASI_POLAR(IM_TETRAHEDRON(8), 2)"));
>>>
>>>
>>>
>>> getfem::model md;
>>> md.add_fem_variable("u", mfu);
>>>
>>>
>>> md.add_initialized_scalar_data("cmu", cmu);
>>> md.add_initialized_scalar_data("clambdastar", clambdastar);
>>>
>>> getfem::add_isotropic_linearized_elasticity_brick
>>>     (md, mim, "u", "clambdastar", "cmu");
>>>
>>>
>>> getfem::add_normal_Dirichlet_condition_with_multipliers(md,mim,"u", 1,
>>> 109);
>>>
>>> getfem::add_source_term_brick(md,mim,"u","[0,1640,0]", 108);
>>>
>>> gmm::iteration iter(residual, 1, 50);
>>> getfem::standard_solve(md, iter,
>>> getfem::rselect_linear_solver(md,"superlu"));
>>>
>>> getfem::standard_solve(md, iter);
>>>
>>> plain_vector U(mfu.nb_dof()); gmm::copy(md.real_variable("u"), U);
>>> plain_vector VM(mfvm.nb_dof());
>>> getfem::compute_isotropic_linearized_Von_Mises_or_Tresca
>>>     (md, "u", "clamabdastar", "cmu", mfvm, VM, false);
>>>
>>>
>>> getfem::vtk_export exp2("d_w_vm.vtk", false);
>>> exp2.exporting(mfu);
>>> exp2.write_point_data(mfu, U, "displacement");
>>> exp2.write_point_data(mfvm, VM, "Von Mises stress");
>>>
>>>
>>> }
>>>
>>
>> Thank you for any help in advance,
>>
>> Andy
>>
>>
>> _______________________________________________
>> Getfem-users mailing
>> address@hidden
>>
>>
>>
>> --
>>
>>   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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