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Re: [Getfem-users] How_to_update_im_data_in_each_loop

From: Andriy Andreykiv
Subject: Re: [Getfem-users] How_to_update_im_data_in_each_loop
Date: Fri, 10 May 2019 10:20:39 +0200

Dear Zhenghuai Guo,

There are several ways. A very concise way is using interpolation functions with _expression_

Interpolation on an im_data object (on the Gauss points of an integration method):

void getfem::ga_interpolation_im_data(md, expr, im_data &imd,
 base_vector &result, const mesh_region &rg=mesh_region::all_convexes());
However, if this, for some reason doesn't work for you, you can simply iterate over elements (or faces) of a region of interest and set
the data on each Gauss point in a loop:

  getfem::mesh mesh;
  getfem::mesh_im im(mesh);
  bgeot::multi_index matrixSize(2, 2);
  auto regionA = 1;
  ImData imDataA(im, matrixSize, regionA);
  PlainVector data(imDataA.nb_tensor_elem() * imDataA.nb_filtered_index());
  for (auto v = getfem::mr_visitor{mesh.region(regionA)}; !v.finished(); ++v)
    for (size_t point = 0; point != imDataA.nb_points_of_element(; ++point)
      bgeot::base_matrix M(2, 2);
      // fill in M
      imDataA.set_matrix(data,, point, M);

you can also set this way ImData for vectors and scalars, of course.

Best regards,

On Fri, 10 May 2019 at 06:21, Zhenghuai Guo <address@hidden> wrote:

Hi, Konstantinos and Yves  and Andriy,

I add a im_data “previous_cauthy_1” to the model. Then in each step of a loop from 1 to 10, I would like to update this im_data. The code sample is as below. Could you please teach me how to update values of the im_data?


getfem::im_data previous_cauthy_1(mim_1);

model.add_im_data("previous_cauthy_1", previous_cauthy_1);

getfem::add_nonlinear_term(model, mim_1,"(lambda_1*Trace(Grad_u_1-previous_cauthy_1)*Id(qdim(u_1)) + mu_1*(Grad_u_1+Grad_u_1'-previous_cauthy_1-previous_cauthy_1')):Grad_Test_u_1" );


for i = 1 to 10:


 getfem::standard_solve(model, iter, solver_name, ls);


update im_data "previous_cauthy_1", for the next loop step




Thank you very much


Zhenghuai Guo

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