<html><head></head><body>Oh yes, Oli is right. You are assembling a nested matrix. On the BC setup you set the entry diagonal entry to 1, but the diagonal entry is a 3x3 matrix, which is the yet to 1 componentwise.<br><br>Best<br>Christian<br><br><div class="gmail_quote">Am 16. April 2020 11:30:10 MESZ schrieb HELFER Thomas 202608 <thomas.helfer@cea.fr>:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<pre class="k9mail">Hi Olivier,<br>I am sorry, I did not understand your point here. I did not want to replace the matrix by a diagonal one,<br>just erase the row corresponding to the component upon which this boundary conditions acts.<br>Have I missed something ?<br>Thomas<hr>De : Dune [dune-bounces@lists.dune-project.org] de la part de Oliver Sander [oliver.sander@tu-dresden.de]<br>Envoyé : jeudi 16 avril 2020 11:11<br>À : dune@lists.dune-project.org<br>Objet : Re: [Dune] Help requested for my first test case in non linear mechanics<br><br>Hi Thomas,<br><br>AFAICT, your method apply_boundary_conditions contains a classic mistake:<br>You are not setting the matrix diagonals correctly. See Chapter 7.3.2.1<br>in my book for details.<br><br>Best,<br>Oliver<br><br>On 16.04.20 09:39, HELFER Thomas 202608 wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> Hi Oliver,<br><br> thanks for this feedback. I will compare my stiffness matrix to the one get with another code,<br> that probably the best way to go. But I felt rather confident...<br><br> But it does seems like something nasty is happening in my code.<br><br> Something is itching me about the linear solver: the defect becomes very high but the solver<br> converges to the given criterion (a reduction to 1.e-5). However, my Dirichlet boundary<br> conditions are not met.<br><br> So either my handling of the Dirichlet boundaryd condtions is wrong, or my usage of the linear solver is<br> (or both).<br><br> Is there an example of how to replace the linear solver by a direct solver ?<br><br> Regards,<br><br> Thomas<hr></blockquote></pre></blockquote></div></body></html>