<div dir="ltr"><div dir="ltr">On Tue, May 17, 2022 at 6:47 PM Toby Isaac <<a href="mailto:toby.isaac@gmail.com">toby.isaac@gmail.com</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>A leaf point is attached to a root point (in a star forest there are only leaves and roots), so that means that a root point would be the point that owns a degree of freedom and a leaf point would have a ghost value.</div><div><br></div><div>For a "point SF" of a DMPlex:</div><div><br></div><div>- Each process has a local numbering of mesh points (cells + edges + faces + vertices): they are all potential roots, so the number of these is what is returned by `nroots`.</div><div><br></div><div>- The number of ghost mesh points is `nleaves`.</div><div><br></div><div>- `ilocal` would be a list of the mesh points that are leaves (using the local numbering).</div><div><br></div><div>- For each leaf in `ilocal`, `iremote` describes the root it is attached to: which process it belongs to, and its id in *that* process's local numbering.</div><div><br></div><div>If you're trying to create dof numberings on your own, please consider PetscSectionCreateGlobalSection: <<a href="https://petsc.org/main/docs/manualpages/PetscSection/PetscSectionCreateGlobalSection/" target="_blank">https://petsc.org/main/docs/manualpages/PetscSection/PetscSectionCreateGlobalSection/</a>>. You supply the PetscSF and a PetscSection which says how many dofs there are for each point and whether any have essential boundary conditions, and it computes a global PetscSection that tells you what the global id is for each dof on this process.</div></div></blockquote><div><br></div><div>Toby is exactly right. Also, if you want global numbering of points you can use</div><div><br></div><div> <a href="https://petsc.org/main/docs/manualpages/DMPLEX/DMPlexCreatePointNumbering/">https://petsc.org/main/docs/manualpages/DMPLEX/DMPlexCreatePointNumbering/</a></div><div><br></div><div>and there is a similar thing for jsut cells or vertices.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, May 17, 2022 at 7:26 PM Ferrand, Jesus A. <<a href="mailto:FERRANJ2@my.erau.edu" target="_blank">FERRANJ2@my.erau.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Dear PETSc team:<br>
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I am working with a non-overlapping distributed plex (i.e., when I call DMPlexDistribute(), I input overlap = 0), so only vertices and edges appear as ghosts to the local ranks.</div>
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For preallocation of a parallel global stiffness matrix for FEA, I want to determine which locally owned vertices are ghosts to another rank.<br>
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>From reading the paper on PetscSF (<a href="https://ieeexplore.ieee.org/document/9442258" id="gmail-m_-7288957893647796504gmail-m_2804447925891900737LPlnkOWALinkPreview" target="_blank">https://ieeexplore.ieee.org/document/9442258</a>) I think I can answer my question by inspecting the PetscSF returned by DMPlexDistribute() with
PetscSFGetGraph(). I am just confused by the root/leaf and ilocal/iremote terminology.
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I read the manual page on PetscSFGetGraph() (<a href="https://petsc.org/release/docs/manualpages/PetscSF/PetscSFGetGraph.html" id="gmail-m_-7288957893647796504gmail-m_2804447925891900737LPlnk343018" target="_blank">https://petsc.org/release/docs/manualpages/PetscSF/PetscSFGetGraph.html</a>) and that gave me the impression that
I need to PetscSFBcast() the point IDs from foreign ranks to the local ones. <br>
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Is this correct?<br>
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<a id="gmail-m_-7288957893647796504gmail-m_2804447925891900737LPImageAnchor149289" href="https://ieeexplore.ieee.org/document/9442258" target="_blank"><img id="gmail-m_-7288957893647796504gmail-m_2804447925891900737LPThumbnailImageId149289" alt="" style="display: block;" src="https://ieeexplore.ieee.org/assets/img/ieee_logo_smedia_200X200.png" width="160" height="160"></a></div>
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<a id="gmail-m_-7288957893647796504gmail-m_2804447925891900737LPUrlAnchor149289" href="https://ieeexplore.ieee.org/document/9442258" style="text-decoration:none" target="_blank">The PetscSF Scalable Communication Layer | IEEE Journals & Magazine | IEEE Xplore</a></div>
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PetscSF, the communication component of the Portable, Extensible Toolkit for Scientific Computation (PETSc), is designed to provide PETSc's communication infrastructure suitable for exascale computers that utilize GPUs and other accelerators. PetscSF provides
a simple application programming interface (API) for managing common communication patterns in scientific computations by using a star ...</div>
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<span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">Sincerely:</span></p>
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<span style="margin:0px;color:red;font-family:"Courier New",monospace;font-size:14pt"><b><span style="font-family:"Courier New",monospace">J.A. Ferrand</span></b></span><u><span style="margin:0px;color:red;font-family:"Swis721 BlkCn BT",sans-serif;font-size:12pt"></span></u></p>
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<span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">Embry-Riddle Aeronautical University - Daytona Beach FL</span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">M.Sc.</span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">
Aerospace Engineering | May 2022</span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">B.Sc.</span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">
Aerospace Engineering</span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">B.Sc.</span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">
Computational Mathematics</span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:rgb(0,0,0);font-family:"Times New Roman",Times,serif;font-size:12pt"> </span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:black;font-family:Courant;font-size:12pt"><span style="color:rgb(0,0,0);font-family:"Times New Roman",Times,serif;font-size:12pt;display:inline;background-color:rgb(255,255,255)">Sigma
Gamma Tau</span><span style="color:rgb(0,0,0);font-family:"Times New Roman",Times,serif;font-size:12pt;display:inline;background-color:rgb(255,255,255)"> </span><br>
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<span style="margin:0px;color:rgb(0,0,0);font-family:"Times New Roman",Times,serif;font-size:12pt">Tau Beta Pi</span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt"> </span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><u><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">Phone:</span></u><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">
(386)-843-1829</span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><u><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">Email(s):</span></u><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt">
<a href="mailto:ferranj2@my.erau.edu" target="_blank">ferranj2@my.erau.edu</a></span></p>
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<span style="font-family:"Times New Roman",Times,serif"></span><span style="margin:0px;color:black;font-family:Courant;font-size:12pt"><span style="margin:0px;font-family:"Times New Roman",Times,serif">
</span></span><span style="margin:0px;color:black;font-family:"Times New Roman",Times,serif;font-size:12pt"><a href="mailto:jesus.ferrand@gmail.com" target="_blank">jesus.ferrand@gmail.com</a></span></p>
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</blockquote></div><br clear="all"><div><br></div>-- <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="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>