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All,</div>
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I'm forwarding Aidan's comments on this issue (see below). Aidan has done extensive study on DMPlex and has been working on hyperbolic flow applications. </div>
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Satish:</div>
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Please add Aidan to petsc-dev mailing list.</div>
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Hong</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Aidan Hamilton <aidan@udel.edu><br>
<b>Sent:</b> Thursday, December 2, 2021 2:34 PM<br>
<b>To:</b> Zhang, Hong <hzhang@mcs.anl.gov><br>
<b>Cc:</b> Sundermann, Rylee Edwin - SDSU Student <rylee.sundermann@jacks.sdstate.edu><br>
<b>Subject:</b> Re: [petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?</font>
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Hong, </p>
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I am not on petsc-dev, I guess I should be. Also you can push, you’re always free to push changes.
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And it doesn’t matter for anything on my end. Each edge is distinct topological entity, so I have the directed graph
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V0 ---- E0 -<span style="font-family:Wingdings"></span> V1 ----- E1 ----<span style="font-family:Wingdings"></span> V0
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I don’t need any special identification. And it works in parallel with globaltolocal seemingly working . Now this is not a standard graph, it follows the more general notion of directed graph, see Diestel page 25, that allows for multi-edges.
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Now for my case I don’t need to distinguish between the two edges at all beyond each one having their own unique edge id. In all of our use cases for traffic I don’t think we need to care (and honestly I’m not sure if Shri actually needs to care either).
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Now we do have the topological distinction of direction for all of our graphs, which we can use to assign direction to traffic flow. And that will always work. And this notion of direction is the only distinction we need to care about, and we have it.
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It’s worth noting that a CW-Complex does support this notion of multiedges, no reason for it not to, so DMPlex should be supporting its topological operations with this case in mind.
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If DMplex can’t support this then dmplex isn’t doing what it claims it does. </p>
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As long as you as the user know that you are dealing with a multi-edge graph, I don’t see why there would be any issues. Any topological query of a multi-edge graph should behave as you would expect a multi-edge graph to behave, though it may behave differently
than single edge graphs, as long as you are aware of the difference when you code your residuals and other functions on dmnetwork it should be fine.
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Best, </p>
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Aidan </p>
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<b><span style="font-size:12.0pt; color:black">From: </span></b><span style="font-size:12.0pt; color:black">Zhang, Hong <hzhang@mcs.anl.gov><br>
<b>Date: </b>Thursday, December 2, 2021 at 1:56 PM<br>
<b>To: </b>Aidan Hamilton <aidan@udel.edu><br>
<b>Cc: </b>Sundermann, Rylee Edwin - SDSU Student <rylee.sundermann@jacks.sdstate.edu><br>
<b>Subject: </b>Fw: [petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?</span></p>
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<span style="font-size:12.0pt; color:black">Aidan,</span></p>
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<span style="font-size:12.0pt; color:black">Are you on petsc-dev email list? </span></p>
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<span style="font-size:12.0pt; color:black">How do you distinguish two parallel edges connecting the same junctions in your traffic code? Do you use </span></p>
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<span style="font-size:12.0pt; color:black">offset_vto, offset_vfrom in EdgeFE?</span></p>
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<span style="font-size:12.0pt; color:black">I removed white spaces in dgnet.c and dgnet.h. Can I push the changes?</span></p>
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<span style="font-size:12.0pt; color:black">Hong</span></p>
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<b><span style="color:black">From:</span></b><span style="color:black"> petsc-dev <petsc-dev-bounces@mcs.anl.gov> on behalf of Barry Smith <bsmith@petsc.dev><br>
<b>Sent:</b> Wednesday, December 1, 2021 7:41 PM<br>
<b>To:</b> Abhyankar, Shrirang G <shrirang.abhyankar@pnnl.gov><br>
<b>Cc:</b> petsc-dev <petsc-dev@mcs.anl.gov>; Betrie, Getnet <gbetrie@anl.gov><br>
<b>Subject:</b> Re: [petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?</span>
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Shri, </p>
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If you provided your graph in parallel I suspect that the GlobalToLocal and LocalToGlobal would not work as you expect and put everything in the appropriate place.</p>
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I'll set up a simple code that takes exactly Get's configuration and send it out so everyone can run it and see exactly what happens.</p>
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Barry</p>
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On Dec 1, 2021, at 8:00 PM, Abhyankar, Shrirang G via petsc-dev <<a href="mailto:petsc-dev@mcs.anl.gov">petsc-dev@mcs.anl.gov</a>> wrote:</p>
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<b><span style="font-size:12.0pt">From:<span class="x_xapple-converted-space"> </span></span></b><span style="font-size:12.0pt">Matthew Knepley <<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>><br>
<b>Date:<span class="x_xapple-converted-space"> </span></b>Wednesday, December 1, 2021 at 5:57 PM<br>
<b>To:<span class="x_xapple-converted-space"> </span></b>"Brown, Jedediah A (VISIT)" <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>><br>
<b>Cc:<span class="x_xapple-converted-space"> </span></b>"Abhyankar, Shrirang G" <<a href="mailto:shrirang.abhyankar@pnnl.gov">shrirang.abhyankar@pnnl.gov</a>>, PETSc Development <<a href="mailto:petsc-dev@mcs.anl.gov">petsc-dev@mcs.anl.gov</a>>, Getnet Betrie
<<a href="mailto:gbetrie@anl.gov">gbetrie@anl.gov</a>><br>
<b>Subject:<span class="x_xapple-converted-space"> </span></b>Re: [petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?</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></p>
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On Wed, Dec 1, 2021 at 6:55 PM Jed Brown <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>> wrote:</p>
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Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>> writes:<br>
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> On Wed, Dec 1, 2021 at 5:17 PM Abhyankar, Shrirang G <<br>
><span class="x_xapple-converted-space"> </span><a href="mailto:shrirang.abhyankar@pnnl.gov" target="_blank">shrirang.abhyankar@pnnl.gov</a>> wrote:<br>
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>> “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>
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This could be modeled with some ghost vertices. So instead of<br>
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a ------ b<br>
\_____/<br>
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you would set up<br>
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a ---o---- b<br>
\___o___/<br>
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Those ghost vertices don't have to "do" anything, but they make the edges topologically distinct.<br>
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Shri, what problems might this cause?</p>
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<span style="font-size:12.0pt; font-family:"Times New Roman",serif">I don’t understand the figure you’ve drawn above. Sorry.</span></p>
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<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?</span></p>
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<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.</span></p>
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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.</p>
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Matt</p>
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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</p>
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<a href="https://www.google.com/url?q=https://gcc02.safelinks.protection.outlook.com/?url%3Dhttp%253A%252F%252Fwww.cse.buffalo.edu%252F~knepley%252F%26data%3D04%257C01%257Cshrirang.abhyankar%2540pnnl.gov%257Cbcbb40fc51f6428ac17708d9b5264361%257Cd6faa5f90ae240338c0130048a38deeb%257C0%257C0%257C637739998211230005%257CUnknown%257CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%253D%257C3000%26sdata%3DSg7eEbjzkSqVd6Sjg8IpTN3iXxMAvih0UNV0fkolO8w%253D%26reserved%3D0&source=gmail-imap&ust=1639079810000000&usg=AOvVaw2q1URmUrcN7rBglSVGeqIH" target="_blank">https://www.cse.buffalo.edu/~knepley/</a></p>
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