<div dir="ltr"><div dir="ltr">On Mon, Feb 9, 2026 at 6:29 AM 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>Hi there,</p>
<p>I am trying to switch btw two different sections (section_l(1:2))
defined on the same DM (one section for the dependent variable,
the other for their gradient)</p>
<p>
</p><blockquote type="cite">
<span style="font-family:monospace"><span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">!</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">!
dependent variables and their nodal gradient</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">!</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)">
PetscCall(DMSetLocalSection(dm, section_l(</span><span style="color:rgb(178,24,24);background-color:rgb(255,255,255)">1</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">), ierr)) </span><span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">! dependent
variables</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)">
PetscCall(DMGetLocalVector(dm, localu, ierr)) </span><span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">! dependent
variables</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)">
PetscCall(DMGlobalto</span><span style="color:rgb(175,95,0);background-color:rgb(255,255,255)">Local</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">(dm, u,
INSERT_VALUES, localu, ierr))</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)">
PetscCall(VecSet(gradu, </span><span style="color:rgb(178,24,24);background-color:rgb(255,255,255)">0.d0</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">, ierr))</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)">
PetscCall(DMSetLocalSection(dm, section_l(</span><span style="color:rgb(178,24,24);background-color:rgb(255,255,255)">2</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">), ierr)) </span><span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">! gradient
of the dependent variables</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)">
PetscCall(DMGetLocalVector(dm, localdu, ierr)) </span><span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">! gradient
of the dependent variables</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)">
PetscCall(VecSet(localdu, </span><span style="color:rgb(178,24,24);background-color:rgb(255,255,255)">0.d0</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">, ierr))</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
<span style="color:rgb(24,24,178);background-color:rgb(255,255,255)">!</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)"> </span><span style="color:rgb(175,95,0);background-color:rgb(255,255,255)">call</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)"> </span><span style="color:rgb(24,178,178);background-color:rgb(255,255,255)">innerloop</span><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">(dm, localu,
localdu, section_l, ierr)</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
</span>
</blockquote>
subroutine innerloop is supposed to do work on both Vecs.<p></p>
<p>When trying to do so, I get the following error:</p>
<p>
</p><blockquote type="cite">
<span style="font-family:monospace"><span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">[0]PETSC
ERROR: --------------------- Error Message
--------------------------------------------------------------</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)">[0]PETSC
ERROR: Object is in wrong state</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)">[0]PETSC
ERROR: Clearing DM of local vectors that has a local vector
obtained with DMGetLocalVector()</span><br>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,255)">
</span><br>
</span>
</blockquote>
as if two sections living simultaneously on the same DM are not
allowed.<p></p>
<p>Should I instead clone the DM and create the "second" section of
the clone?</p>
<p></p></div></blockquote><div>Yes, this is exactly right. It is lightweight, and this is what clone is intended for.</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
web: <a href="https://urldefense.us/v3/__http://docenti.unibas.it/site/home/docente.html?m=002423__;!!G_uCfscf7eWS!YVPmxuMFuutpshSi89LXW-8W6oF1lauFcuN2HzqwcvecXbGkhDoRlhVqyIdHvFHEXN7_zUPSCbdoeElWRBtO1fQ_1q-v4pzF0QU$" target="_blank">http://docenti.unibas.it/site/home/docente.html?m=002423</a></pre>
</div>
</blockquote></div><div><br clear="all"></div><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener</div><div><br></div><div><a href="https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!aoLehySjF-RiaGi_oyCRn_dYj6QvTlk5w028Xwvyvfl42tLcztJ0dySq0cpcEjn2g2b_md_LL-09JYjpzJhA$" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>