Sorry either your mail system or mine prevented me from attaching the file, so I put it on pastebin: https://pastebin.com/awFpc1Js
On Wed, Jan 11, 2023 at 4:54 PM Matthew Knepley <[email protected]> wrote: > Can you send the .msh file? I still have not installed Gmsh :) > > Thanks, > > Matt > > On Wed, Jan 11, 2023 at 2:43 PM Daniel R. Shapero <[email protected]> wrote: > >> Hi all -- I'm trying to read in 2nd-order / piecewise quadratic meshes >> that are generated by gmsh and I don't understand how the coordinates are >> stored in the plex. I've been discussing this with Matt Knepley here >> <https://urldefense.com/v3/__https://github.com/firedrakeproject/firedrake/issues/982__;!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2gOStva7A$> >> as it pertains to Firedrake but I think this is more an issue at the PETSc >> level. >> >> This code >> <https://urldefense.com/v3/__https://gist.github.com/danshapero/a140daaf951ba58c48285ec29f5973cc__;!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2hho2eD1g$> >> uses gmsh to generate a 2nd-order mesh of the unit disk, read it into a >> DMPlex, print out the number of cells in each depth stratum, and finally >> print a view of the coordinate DM's section. The resulting mesh has 64 >> triangles, 104 edges, and 41 vertices. For 2nd-order meshes, I'd expected >> there to be 2 degrees of freedom at each node and 2 at each edge. The >> output is: >> >> ``` >> Depth strata: [(64, 105), (105, 209), (0, 64)] >> >> PetscSection Object: 1 MPI process >> type not yet set >> 1 fields >> field 0 with 2 components >> Process 0: >> ( 0) dim 12 offset 0 >> ( 1) dim 12 offset 12 >> ( 2) dim 12 offset 24 >> ... >> ( 62) dim 12 offset 744 >> ( 63) dim 12 offset 756 >> ( 64) dim 0 offset 768 >> ( 65) dim 0 offset 768 >> ... >> ( 207) dim 0 offset 768 >> ( 208) dim 0 offset 768 >> PetscSectionSym Object: 1 MPI process >> type: label >> Label 'depth' >> Symmetry for stratum value 0 (0 dofs per point): no symmetries >> Symmetry for stratum value 1 (0 dofs per point): no symmetries >> Symmetry for stratum value 2 (12 dofs per point): >> Orientation range: [-3, 3) >> Symmetry for stratum value -1 (0 dofs per point): no symmetries >> ``` >> >> The output suggests that there are 12 degrees of freedom in each >> triangle. That would mean the coordinate field is discontinuous across cell >> boundaries. Can someone explain what's going on? I tried reading the .msh >> file but it's totally inscrutable to me. I'm happy to RTFSC if someone >> points me in the right direction. Matt tells me that the coordinate field >> should only be discontinuous if the mesh is periodic, but this mesh >> shouldn't be periodic. >> > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > > https://www.cse.buffalo.edu/~knepley/ > <https://urldefense.com/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!K-Hz7m0Vt54!hL9WLR51ieyHFZx8N9AjhDwJCRpvmQto9CL1XOTkkAxFfUbtsabHuBDOATnWyP6lQszhA2go23tjRg$> >
