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<p>Hi Matthew,</p>
<p>I have joined the ex44.c example so you can see that we see.</p>
<p>The problem is about the "f" field number which I can't see any clue in the documentation to what to put there... We are missing some information maybe written elsewhere?</p>
<p>I have tried 3 different calls (lines 180-182) with comments aside:
</p>
<p> //ierr = DMSetBasicAdjacency(ddm, PETSC_TRUE, PETSC_FALSE); CHKERRQ(ierr); //This works: it give only 2 cells for the overlap
//ierr = DMSetAdjacency(ddm, 0, PETSC_TRUE, PETSC_FALSE); CHKERRQ(ierr); //This works too, but why do I have to use field #0 ??? Is it a convention?
ierr = DMSetAdjacency(ddm, PETSC_DEFAULT, PETSC_TRUE, PETSC_FALSE); CHKERRQ(ierr); //This does not works: it give 3 cells for the overlap instead of 2.
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;">Also, do you think your gitlab/knepley/fix-plex-g2n branch will find it's way into next or main? ;)</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;">Thanks,</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;">Eric</p>
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<div class="moz-cite-prefix">On 2021-11-10 3:26 p.m., Matthew
Knepley wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAMYG4G=69JUcemHUi9_B6ajtqHhp5knqEt2svkRf_ktHv2Jw9A@mail.gmail.com">
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<div dir="ltr">Okay, so the PETSC_DEFAULT one is what is used for
topology. There are two separate uses for adjacency info.
<div class="gmail_quote">
<div>First, for this kind of topological extension, and the
second is for calculating Jacobians. You should be able to
see</div>
<div>the difference between FEM and FVM in just the case of a
2x2 mesh where each process gets 1 cell. With FEM,</div>
<div>the overlap is the whole mesh, whereas with FVM it leaves
out the diagonal partner.</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
</div>
</div>
</blockquote>
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