Hi Matt and Jed,
Thanks for your replies. I did not consider that distinction Matt, that makes clearer. Maybe it's time to the DAG-stuff on the documentation another attempt... Jed, could you point me in the direction of a possible solution to this, if there exists one? In my (FEM) application I'm not using the weak-form stuff, but do I use PetscFE to describe my data layout and access it with DMPlexVec(Mat)Set(Get)Closure and friends. Thanks! Vilmer ________________________________ Från: Matthew Knepley <[email protected]> Skickat: den 15 maj 2023 15:42:20 Till: Jed Brown Kopia: Vilmer Dahlberg; [email protected] Ämne: Re: [petsc-users] Issues creating DMPlex from higher order mesh generated by gmsh On Mon, May 15, 2023 at 9:30 AM Jed Brown <[email protected]<mailto:[email protected]>> wrote: Matthew Knepley <[email protected]<mailto:[email protected]>> writes: > On Fri, May 5, 2023 at 10:55 AM Vilmer Dahlberg via petsc-users < > [email protected]<mailto:[email protected]>> wrote: > >> Hi. >> >> >> I'm trying to read a mesh of higher element order, in this example a mesh >> consisting of 10-node tetrahedral elements, from gmsh, into PETSC. But It >> looks like the mesh is not properly being loaded and converted into a >> DMPlex. gmsh tells me it has generated a mesh with 7087 nodes, but when I >> view my dm object it tells me it has 1081 0-cells. This is the printout I >> get >> > > Hi Vilmer, > > Plex makes a distinction between topological entities, like vertices, edges > and cells, and the function spaces used to represent fields, like velocity > or coordinates. When formats use "nodes", they mix the two concepts > together. > > You see that if you add the number of vertices and edges, you get 7087, > since for P2 there is a "node" on every edge. Is anything else wrong? Note that quadratic (and higher order) tets are broken with the Gmsh reader. It's been on my todo list for a while. As an example, this works when using linear elements (the projection makes them quadratic and visualization is correct), but is tangled when holes.msh is quadratic. $ $PETSC_ARCH/tests/dm/impls/plex/tutorials/ex1 -dm_plex_filename ~/meshes/holes.msh -dm_view cgns:s.cgns -dm_coord_petscspace_degree 2 Projection to the continuous space is broken because we do not have the lexicographic order on simplicies done. Are you sure you are projecting into the broken space? Thanks, Matt -- 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/>
