On Thu, Jan 12, 2023 at 3:57 PM Blaise Bourdin <[email protected]> wrote:
> Out of curiosity, what is the rationale for _reading_ high order gmsh > meshes? > Is it so that one can write data back in native gmsh format? > So we can use meshes that other people design I think. Matt > Regards, > Blaise > > > On Jan 12, 2023, at 7:13 PM, Matthew Knepley <[email protected]> wrote: > > On Thu, Jan 12, 2023 at 1:33 PM Jed Brown <[email protected]> wrote: > >> 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(), > > > 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. > > It does look like higher order Gmsh does read as DG. We can just project > that to CG for non-periodic stuff. > > Thanks, > > Matt > > which should simplify the code and avoid the confusing cell coordinates >> pattern. Sadly, I don't have time to dive in. >> >> >> https://gitlab.com/petsc/petsc/-/commit/066ea43f7f75752f012be6cd06b6107ebe84cc6d#3616cad8148970af5b97293c49492ff893e25b59_1552_1724 >> >> "Daniel R. Shapero" <[email protected]> writes: >> >> > 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$ >> > >> >> >> > > > -- > 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/ > <http://www.cse.buffalo.edu/~knepley/> > > > — > Canada Research Chair in Mathematical and Computational Aspects of Solid > Mechanics (Tier 1) > Professor, Department of Mathematics & Statistics > Hamilton Hall room 409A, McMaster University > 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada > https://www.math.mcmaster.ca/bourdin | +1 (905) 525 9140 ext. 27243 > > -- 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/ <http://www.cse.buffalo.edu/~knepley/>
