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<div class="moz-cite-prefix">On 10/6/25 20:10, Matthew Knepley
wrote:<br>
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cite="mid:CAMYG4G=ayJck4N0ZF1cQEM+P47DNoRpZm-a8SdSmbLn0P2xLRw@mail.gmail.com">
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<div dir="ltr">On Mon, Oct 6, 2025 at 1:11 PM Aldo Bonfiglioli
<<a href="mailto:aldo.bonfiglioli@unibas.it"
moz-do-not-send="true" class="moz-txt-link-freetext">aldo.bonfiglioli@unibas.it</a>>
wrote:</div>
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<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>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>
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<div><br>
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<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>
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<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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<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>
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<div><a href="https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!Yk-uGKnWGfd4b87jjp07cII-ta6Rld0p_kmImii1ZuYnG2DCFwjpUQkeQ8z3mrWOHPd6-oKoBkZsW8rkoKSWFblHNxPy-jdNsBo$" target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
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<p>Matthew,</p>
<p>I followed your suggestions, but I face a deadlock when the
enclosed demonstrator is run in parallel (for the attached
dotfile, deadlock occurs when nproc = 3).</p>
<p>I suspect it might be due to the fact that in a parallel
environment the various strata of the "Face Sets" are not
necessarily available to all processes.</p>
<p>Therefore, not all processes are going to call
DMPlexCreateSubmesh with a given "value". </p>
<p>The attached piece of code links with petsc-3.24.0.</p>
<p>Thanks,</p>
<p>Aldo</p>
<p><br>
</p>
<pre class="moz-signature" cols="72">--
Dr. Aldo Bonfiglioli
Associate professor of Fluid Mechanics
Dipartimento di Ingegneria
Universita' della Basilicata
V.le dell'Ateneo Lucano, 10 85100 Potenza ITALY
tel:+39.0971.205203 fax:+39.0971.205215
web: <a class="moz-txt-link-freetext" href="https://urldefense.us/v3/__http://docenti.unibas.it/site/home/docente.html?m=002423__;!!G_uCfscf7eWS!Yk-uGKnWGfd4b87jjp07cII-ta6Rld0p_kmImii1ZuYnG2DCFwjpUQkeQ8z3mrWOHPd6-oKoBkZsW8rkoKSWFblHNxPyamZ0CHI$">http://docenti.unibas.it/site/home/docente.html?m=002423</a></pre>
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