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    <div class="moz-cite-prefix">Ok, I think what I will do is the
      following:<br>
      <br>
      <div>
        <div>void top_bc(const PetscReal x[], PetscScalar *u, void *ctx)</div>
        <div>{</div>
        <div>  *u = 0.2;</div>
        <div>}</div>
      </div>
      <div>
        <div>
          <div>void bottom_bc(const PetscReal x[], PetscScalar *u, void
            *ctx)</div>
          <div>{</div>
          <div>  *u = 0.0;</div>
          <div>}</div>
        </div>
      </div>
      <br>
      <br>
      ierr = DMPlexAddBoundary(dm, PETSC_TRUE,"bottom","Face
      Sets",0,(void (*)())bottom_bc,1,ids[0],&user);CHKERRQ(ierr);<br>
      ierr = DMPlexAddBoundary(dm, PETSC_TRUE,"top","Face Sets",0,(void
      (*)())top_bc,1,ids[1],&user);CHKERRQ(ierr);<br>
      <br>
      Matt, have you started writing some documentation for these
      function?<br>
      If not I could probably get something started since I'm reading
      them.<br>
      <br>
      Another question, how do I explain to my DMPlex that I am solving
      an elasticity problem and hence my solution field will be a 2
      components vector and not a scalar? I haven't seen where you set
      this info in snes example 12...<br>
      <pre class="moz-signature" cols="72">Best,
Luc</pre>
      On 01/22/2015 05:19 PM, Matthew Knepley wrote:<br>
    </div>
    <blockquote
cite="mid:CAMYG4G=4P-QvO2xxXAMEeDRDKsCmqHmH35Mm37wq8WAJpNfDQQ@mail.gmail.com"
      type="cite">
      <div dir="ltr">
        <div class="gmail_extra">
          <div class="gmail_quote">On Thu, Jan 22, 2015 at 4:17 PM, Luc
            Berger-Vergiat <span dir="ltr"><<a
                moz-do-not-send="true" href="mailto:lb2653@columbia.edu"
                target="_blank">lb2653@columbia.edu</a>></span>
            wrote:<br>
            <blockquote class="gmail_quote" style="margin:0 0 0
              .8ex;border-left:1px #ccc solid;padding-left:1ex">
              <div bgcolor="#FFFFFF" text="#000000">
                <div>Yes you are right, I corrected for the machine
                  epsilon.<br>
                  I also looked deeper in Petsc's source code and I
                  think I understand better how you implemented the GMSH
                  reader.<br>
                  For instance the label I really care about is "Face
                  Sets" since it detects automatically the BC's for me.<br>
                  An issue is that "Face Sets" contains 4 strata and I
                  only care about two of these strata.<br>
                  How can I get the names of the Strata and how can I
                  loop over the strata to assign my BCs?<br>
                </div>
              </div>
            </blockquote>
            <div><br>
            </div>
            <div>Instead of "marker" give "Face Sets"</div>
            <div><br>
            </div>
            <div>Instead of 1, give 2</div>
            <div><br>
            </div>
            <div>Instead of &id give ids, where PetscInt ids[2] =
              {stratumValue1, stratumValue2}</div>
            <div><br>
            </div>
            <div>  Thanks,</div>
            <div><br>
            </div>
            <div>    Matt</div>
            <div> </div>
            <blockquote class="gmail_quote" style="margin:0 0 0
              .8ex;border-left:1px #ccc solid;padding-left:1ex">
              <div bgcolor="#FFFFFF" text="#000000">
                <div>
                  <pre cols="72">Best,
Luc</pre>
                  On 01/22/2015 05:12 PM, Matthew Knepley wrote:<br>
                </div>
                <blockquote type="cite">
                  <div dir="ltr">
                    <div class="gmail_extra">
                      <div class="gmail_quote">On Thu, Jan 22, 2015 at
                        12:08 PM, Luc Berger-Vergiat <span dir="ltr"><<a
                            moz-do-not-send="true"
                            href="mailto:lb2653@columbia.edu"
                            target="_blank">lb2653@columbia.edu</a>></span>
                        wrote:<br>
                        <blockquote class="gmail_quote"
                          style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Hi

                          all,<br>
                          I'm trying to test some functionalities in
                          DMPlex, specifically I want to do a 2d fem
                          simulation using a mesh generated by GMSH.<br>
                          At this point I am trying to understand how
                          Dirichlet BC can be applied.<br>
                          <br>
                          Can you explain to me what arguments I have to
                          pass to:<br>
                          DMPlexAddBoundary()?<br>
                        </blockquote>
                        <div><br>
                        </div>
                        <div>
                          <div>  ierr = DMPlexAddBoundary(dm,
                            PETSC_TRUE,"wall","marker",(void
                            (*)())top_displacement,1,&id,user)</div>
                        </div>
                        <div><br>
                        </div>
                        <div>PETSC_TRUE means that these unknowns will
                          be eliminated from the global system</div>
                        <div><br>
                        </div>
                        <div>"wall" is the name of the BC</div>
                        <div><br>
                        </div>
                        <div>"marker" is the name of the DMLabel that
                          you want to use to identify the mesh points</div>
                        <div><br>
                        </div>
                        <div>1 is the number of label IDs that identify
                          constrained mesh points</div>
                        <div><br>
                        </div>
                        <div>id is the label ID which identifies
                          constrained mesh points</div>
                        <div><br>
                        </div>
                        <div>top_displacement is the function used to
                          set boundary values</div>
                        <div> </div>
                        <blockquote class="gmail_quote"
                          style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">I
                          am attaching a little bit of c code and my
                          mesh.geo and mesh.msh so that you understand
                          the context.<br>
                          The BCs I want to apply are displacement of
                          0.2 in the y direction if y==1.0<br>
                          0.0 in the x direction if y==0.0</blockquote>
                        <div><br>
                        </div>
                        <div>I might do this:</div>
                        <div><br>
                        </div>
                        <div>
                          <div>void top_displacement(const PetscReal
                            x[], PetscScalar *u, void *ctx)</div>
                          <div>{</div>
                          <div>  *u = x[1] < PETSC_MACHINE_EPSILON ?
                            0.0 : 0.2;</div>
                          <div>}</div>
                        </div>
                        <div><br>
                        </div>
                        <div>  Thanks,</div>
                        <div><br>
                        </div>
                        <div>     Matt</div>
                        <div> </div>
                        <blockquote class="gmail_quote"
                          style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><span><font
                              color="#888888"><br>
                              <span class="HOEnZb"><font color="#888888">
                                  -- <br>
                                  Best,<br>
                                  Luc<br>
                                  <br>
                                </font></span></font></span></blockquote>
                        <span class="HOEnZb"><font color="#888888"> </font></span></div>
                      <span class="HOEnZb"><font color="#888888"> <br>
                          <br clear="all">
                          <div><br>
                          </div>
                          -- <br>
                          <div>What most experimenters take for granted
                            before they begin their experiments is
                            infinitely more interesting than any results
                            to which their experiments lead.<br>
                            -- Norbert Wiener</div>
                        </font></span></div>
                  </div>
                </blockquote>
                <br>
              </div>
            </blockquote>
          </div>
          <br>
          <br clear="all">
          <div><br>
          </div>
          -- <br>
          <div class="gmail_signature">What most experimenters take for
            granted before they begin their experiments is infinitely
            more interesting than any results to which their experiments
            lead.<br>
            -- Norbert Wiener</div>
        </div>
      </div>
    </blockquote>
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