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<p class="MsoNormal" style="margin-left:.5in"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Matthew Knepley <knepley@gmail.com><br>
<b>Date: </b>Wednesday, December 1, 2021 at 5:57 PM<br>
<b>To: </b>"Brown, Jedediah A (VISIT)" <jed@jedbrown.org><br>
<b>Cc: </b>"Abhyankar, Shrirang G" <shrirang.abhyankar@pnnl.gov>, PETSc Development <petsc-dev@mcs.anl.gov>, Getnet Betrie <gbetrie@anl.gov><br>
<b>Subject: </b>Re: [petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?<o:p></o:p></span></p>
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<span style="font-family:"Arial",sans-serif;color:black">Check twice before you click! This email originated from outside PNNL.</span><span style="font-family:"Arial",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in">On Wed, Dec 1, 2021 at 6:55 PM Jed Brown <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>> writes:<br>
<br>
> On Wed, Dec 1, 2021 at 5:17 PM Abhyankar, Shrirang G <<br>
> <a href="mailto:shrirang.abhyankar@pnnl.gov" target="_blank">shrirang.abhyankar@pnnl.gov</a>> wrote:<br>
><br>
>> “You can certainly have many fields on a given edge, but I don't know<br>
>> what it would mean to have two edges since no topological query could tell<br>
>> the difference.”<br>
>><br>
>><br>
>><br>
>> The two edges in a power grid represent two parallel power lines that are<br>
>> connected between two locations (vertices). There are line ids (stored in<br>
>> the component data) to distinguish the two lines.<br>
>><br>
><br>
> Yes, so you can tell the difference in the function space (since difference<br>
> current passes down each one), but _topologically_ you cannot. If you put<br>
> duplicate cells in, then<br>
> some topological queries will give unexpected results, like the join of the<br>
> two vertices.<br>
<br>
This could be modeled with some ghost vertices. So instead of<br>
<br>
a ------ b<br>
\_____/<br>
<br>
you would set up<br>
<br>
a ---o---- b<br>
\___o___/<br>
<br>
Those ghost vertices don't have to "do" anything, but they make the edges topologically distinct.<br>
<br>
Shri, what problems might this cause?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">I don’t understand the figure you’ve drawn above. Sorry.
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">As a user, would I need to add anything to the way I am setting up the network/plex or any additional equations in the residual evaluation?
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif">I do not have any issue right now for the power grid problem since I don’t require DMNetwork or DMPLEX to do the topological distinction between parallel edges. There are
unique edge identifiers in my dataset through which I can make this distinction.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in">Yes, this would work, but it looks like the multiple cells are not causing them problems right now with the questions they are asking the mesh.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"> Matt<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">-- <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in">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<o:p></o:p></p>
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