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Re: [Getfem-users] gmres did not converge!

From: Zhenghuai Guo
Subject: Re: [Getfem-users] gmres did not converge!
Date: Thu, 2 May 2019 13:52:02 +0000

Hi Kostas,


Thank you for the advice.


Sorry to be stupid. But I have not use MUMPS before. And I haven’t fond any example showing how to use/call it in a getfem code. As I understand, in order to use it I should


  1. Add the following in ./configure stage when install getfem


--with-mumps-include-dir=" -I /path/to/MUMPS/include "
--with-mumps=" F90 libraries and libs of MUMPS to be linked "


              (as indicated in page 5 in getfem User Documentation version5.3)



  1. Then I can use it



Is this procedure correct? Or do I need to install MUMPS separately?


Thank you very much


Zhenghuai Guo


From: Konstantinos Poulios <address@hidden>
Sent: Thursday, May 2, 2019 11:04 PM
To: Zhenghuai Guo <address@hidden>
Cc: Yves Renard <address@hidden>; getfem-users <address@hidden>
Subject: Re: [Getfem-users] gmres did not converge!


Dear Zhenghuai Guo,


Why don't you use a direct solver (MUMPS)? Direct solvers are much more robust, especially if your model contains Lagrange multipliers.





On Thu, May 2, 2019 at 2:57 PM Zhenghuai Guo <address@hidden> wrote:

Hi, Andriy and Yves and Konstantinos,

I loaded two meshes, totally about 350000 elements.

I only added elasticity bricks:
  getfem::add_isotropic_linearized_elasticity_brick(model, mim_1, "u_1", "lambda_1", "mu_1");
  getfem::add_isotropic_linearized_elasticity_brick(model, mim_2, "u_2", "lambda_2", "mu_2");

and four pointwise_constraints (two more each mesh):
  getfem::add_pointwise_constraints_with_multipliers(model,"u_1","point_1_1","point_1_1_unitx", "point_1_1_valuex");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_1","point_1_1","point_1_1_unity", "point_1_1_valuey");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_1","point_1_2","point_1_2_unitx", "point_1_2_valuex");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_1","point_1_2","point_1_2_unity", "point_1_2_valuey");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_2","point_2_1","point_2_1_unitx", "point_2_1_valuex");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_2","point_2_1","point_2_1_unity", "point_2_1_valuey");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_2","point_2_2","point_2_2_unitx", "point_2_2_valuex");
  getfem::add_pointwise_constraints_with_multipliers(model,"u_2","point_2_2","point_2_2_unity", "point_2_2_valuey");

 The values for the pointwise_constraints are simply the same as -1. This means the two meshes should just be translated parallelly by -1 in both x and y direction.

My solver is
  gmm::iteration iter(1E-9, 1, 100);
  getfem::standard_solve(model, iter);

But I get warning of not convergence:
iter   0 residual            1
 iter 500 residual  6.17288e-05
Level 2 Warning in getfem/getfem_model_solvers.h, line 127: gmres did not converge!

I am quite sure that my mesh looks good and have no strange shape elements. When I use small simply meshes, the code runs ok.
Could you please advise to me how to improve?

Zhenghuai Guo

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