<div dir="ltr"><div dir="ltr">On Mon, Oct 6, 2025 at 1:11 PM Aldo Bonfiglioli <<a href="mailto:aldo.bonfiglioli@unibas.it">aldo.bonfiglioli@unibas.it</a>> wrote:</div><div class="gmail_quote gmail_quote_container"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<p>Dear all,</p>
<p>what is the best approach for defining vectors that "sit" on the
(vertices and/or faces) of a given stratum of the "Face Sets" of a
DMPlex?</p>
<p>
</p><blockquote type="cite">
<span style="font-family:monospace"><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">DM Object:
3D plex 1 MPI process</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> type:
plex</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">3D plex
in 3 dimensions:</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> Number
of 0-cells per rank: 9261</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> Number
of 1-cells per rank: 59660</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> Number
of 2-cells per rank: 98400</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> Number
of 3-cells per rank: 48000</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">Labels:</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
marker: 1 strata with value/size (1 (14402))</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
celltype: 4 strata with value/size (0 (9261), 1 (59660), 3
(98400), 6 (48000))</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> depth:
4 strata with value/size (0 (9261), 1 (59660), 2 (98400), 3
(48000))</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> Face
Sets: 6 strata with value/size (1 (800), 2 (800), 3 (800), 4
(800), 5 (800), 6 (800))</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
</span>
</blockquote>
These vectors are going to be used (for example) to store stresses
and heat flux on solid surfaces.<p></p>
<p>To be more specific: suppose stratum 3 of the "Face Sets" is a
solid wall. </p>
<p>I want to create a vector that that stores quantities computed on
the (800) faces of that wall OR the vertices of that wall.</p></div></blockquote><div><br></div><div>It should be simple to just create such vectors. You request a submesh using that label</div><div><br></div><div> DM subdm;</div><div> DMLabel label, sublabel;</div><div><br></div><div> DMGetLabel(dm, "Face Sets", &label);</div><div> DMLabelDuplicate(label, &sublabel);</div><div> DMPlexLabelComplete(dm, sublabel);</div><div> DMPlexCreateSubmesh(dm, sublabel, 3, PETSC_TRUE, &subdm)</div><div> DMLabelDestroy(&sublabel);</div><div><br></div><div>Now you can define a PetscFE over this submesh in the same way as any other mesh. Moreover, the subdm contains a mapping back to the original DM, from which you can create a mapping of dofs, so that you can inject the subvector into a larger field if you wish.</div><div><br></div><div>If you want to use fields on submeshes inside a PetscDS, so that the Plex manages the solve, the procedure is slightly different, but I can detail it if you want.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div>
<p>Thanks,</p>
<p>Aldo </p>
<pre cols="72">--
Dr. Aldo Bonfiglioli
Associate professor of Fluid Mechanics
Dipartimento di Ingegneria
Universita' della Basilicata
V.le dell'Ateneo Lucano, 10 85100 Potenza ITALY
tel:+39.0971.205203 fax:+39.0971.205215
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</blockquote></div><div><br clear="all"></div><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><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><div><br></div><div><a href="https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!agxuKTesyLfH3uplL5jGjn6KTo6lQTqlAtD7aN9x4Nao7Q1B1yi933LeiaBDdRvOl-Eusg-tJFIjzd0H4x8r$" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>