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Out of curiosity, what is the rationale for _reading_ high order gmsh meshes?
<div>Is it so that one can write data back in native gmsh format? </div>
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<div>Regards,</div>
<div>Blaise</div>
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<div>On Jan 12, 2023, at 7:13 PM, Matthew Knepley <knepley@gmail.com> wrote:</div>
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<div dir="ltr">On Thu, Jan 12, 2023 at 1:33 PM Jed Brown <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>> wrote:<br>
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It's confusing, but this line makes high order simplices always read as discontinuous coordinate spaces. I would love if someone would revisit that, perhaps also using DMPlexSetIsoperiodicFaceSF(),</blockquote>
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<div>Perhaps as a switch, but there is no way I am getting rid of the current periodicity. As we have discussed before, breaking the topological relation is a non-starter for me.</div>
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<div>It does look like higher order Gmsh does read as DG. We can just project that to CG for non-periodic stuff.</div>
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<div> Thanks,</div>
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<div> Matt</div>
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which should simplify the code and avoid the confusing cell coordinates pattern. Sadly, I don't have time to dive in.<br>
<br>
<a href="https://gitlab.com/petsc/petsc/-/commit/066ea43f7f75752f012be6cd06b6107ebe84cc6d#3616cad8148970af5b97293c49492ff893e25b59_1552_1724" rel="noreferrer" target="_blank">https://gitlab.com/petsc/petsc/-/commit/066ea43f7f75752f012be6cd06b6107ebe84cc6d#3616cad8148970af5b97293c49492ff893e25b59_1552_1724</a><br>
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"Daniel R. Shapero" <<a href="mailto:shapero@uw.edu" target="_blank">shapero@uw.edu</a>> writes:<br>
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> Sorry either your mail system or mine prevented me from attaching the file,<br>
> so I put it on pastebin:<br>
><span class="Apple-converted-space"> </span><a href="https://pastebin.com/awFpc1Js" rel="noreferrer" target="_blank">https://pastebin.com/awFpc1Js</a><br>
><br>
> On Wed, Jan 11, 2023 at 4:54 PM Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>> wrote:<br>
><br>
>> Can you send the .msh file? I still have not installed Gmsh :)<br>
>><br>
>> Thanks,<br>
>><br>
>> Matt<br>
>><br>
>> On Wed, Jan 11, 2023 at 2:43 PM Daniel R. Shapero <<a href="mailto:shapero@uw.edu" target="_blank">shapero@uw.edu</a>> wrote:<br>
>><br>
>>> Hi all -- I'm trying to read in 2nd-order / piecewise quadratic meshes<br>
>>> that are generated by gmsh and I don't understand how the coordinates are<br>
>>> stored in the plex. I've been discussing this with Matt Knepley here<br>
>>> <<a href="https://urldefense.com/v3/__https://github.com/firedrakeproject/firedrake/issues/982__;!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2gOStva7A$" rel="noreferrer" target="_blank">https://urldefense.com/v3/__https://github.com/firedrakeproject/firedrake/issues/982__;!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2gOStva7A$</a>><br>
>>> as it pertains to Firedrake but I think this is more an issue at the PETSc<br>
>>> level.<br>
>>><br>
>>> This code<br>
>>> <<a href="https://urldefense.com/v3/__https://gist.github.com/danshapero/a140daaf951ba58c48285ec29f5973cc__;!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2hho2eD1g$" rel="noreferrer" target="_blank">https://urldefense.com/v3/__https://gist.github.com/danshapero/a140daaf951ba58c48285ec29f5973cc__;!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2hho2eD1g$</a>><br>
>>> uses gmsh to generate a 2nd-order mesh of the unit disk, read it into a<br>
>>> DMPlex, print out the number of cells in each depth stratum, and finally<br>
>>> print a view of the coordinate DM's section. The resulting mesh has 64<br>
>>> triangles, 104 edges, and 41 vertices. For 2nd-order meshes, I'd expected<br>
>>> there to be 2 degrees of freedom at each node and 2 at each edge. The<br>
>>> output is:<br>
>>><br>
>>> ```<br>
>>> Depth strata: [(64, 105), (105, 209), (0, 64)]<br>
>>><br>
>>> PetscSection Object: 1 MPI process<br>
>>> type not yet set<br>
>>> 1 fields<br>
>>> field 0 with 2 components<br>
>>> Process 0:<br>
>>> ( 0) dim 12 offset 0<br>
>>> ( 1) dim 12 offset 12<br>
>>> ( 2) dim 12 offset 24<br>
>>> ...<br>
>>> ( 62) dim 12 offset 744<br>
>>> ( 63) dim 12 offset 756<br>
>>> ( 64) dim 0 offset 768<br>
>>> ( 65) dim 0 offset 768<br>
>>> ...<br>
>>> ( 207) dim 0 offset 768<br>
>>> ( 208) dim 0 offset 768<br>
>>> PetscSectionSym Object: 1 MPI process<br>
>>> type: label<br>
>>> Label 'depth'<br>
>>> Symmetry for stratum value 0 (0 dofs per point): no symmetries<br>
>>> Symmetry for stratum value 1 (0 dofs per point): no symmetries<br>
>>> Symmetry for stratum value 2 (12 dofs per point):<br>
>>> Orientation range: [-3, 3)<br>
>>> Symmetry for stratum value -1 (0 dofs per point): no symmetries<br>
>>> ```<br>
>>><br>
>>> The output suggests that there are 12 degrees of freedom in each<br>
>>> triangle. That would mean the coordinate field is discontinuous across cell<br>
>>> boundaries. Can someone explain what's going on? I tried reading the .msh<br>
>>> file but it's totally inscrutable to me. I'm happy to RTFSC if someone<br>
>>> points me in the right direction. Matt tells me that the coordinate field<br>
>>> should only be discontinuous if the mesh is periodic, but this mesh<br>
>>> shouldn't be periodic.<br>
>>><br>
>><br>
>><br>
>> --<br>
>> What most experimenters take for granted before they begin their<br>
>> experiments is infinitely more interesting than any results to which their<br>
>> experiments lead.<br>
>> -- Norbert Wiener<br>
>><br>
>><span class="Apple-converted-space"> </span><a href="https://www.cse.buffalo.edu/~knepley/" rel="noreferrer" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br>
>> <<a href="https://urldefense.com/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2go23tjRg$" rel="noreferrer" target="_blank">https://urldefense.com/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2go23tjRg$</a>><br>
>><br>
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<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>
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Canada Research Chair in Mathematical and Computational Aspects of Solid Mechanics (Tier 1)</div>
<div>Professor, Department of Mathematics & Statistics<br>
Hamilton Hall room 409A, McMaster University<br>
1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada <br>
https://www.math.mcmaster.ca/bourdin | +1 (905) 525 9140 ext. 27243</div>
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