[petsc-users] DMPlex and Boundary facets

[Lawrence Mitchell]

> On 19 May 2021, at 14:46, Karin&NiKo <niko.karin at gmail.com> wrote:
> 
> Dear Matthew,
> 
> You are (again) right. This Gmsh test file is "dirty" : some triangles do not belong to tests. Sorry for that.
> I have tried with another geo file (which is clean in that sense) and PETSc reads with no error.
> 
> I take this opportunity to ask my initial question : are the labels of the Physical Entities saved somewhere ? 
> A gmsh test file with several Physical entities is attached to this email. 

Yes, plex represents Physical entities as "labels". In particular, for facets, they are loaded as the "Face Sets" label, plex also loads markers on cells in the "Cell Sets" label.

e.g. here's the DMView output of your mesh.

DM Object: DM_0x84000000_0 1 MPI processes
  type: plex
DM_0x84000000_0 in 3 dimensions:
  0-cells: 64
  1-cells: 279
  2-cells: 378
  3-cells: 162
Labels:
  celltype: 4 strata with value/size (0 (64), 6 (162), 3 (378), 1 (279))
  depth: 4 strata with value/size (0 (64), 1 (279), 2 (378), 3 (162))
  Cell Sets: 1 strata with value/size (7 (162))
  Face Sets: 6 strata with value/size (3 (18), 6 (18), 2 (18), 5 (18), 1 (18), 4 (18))


Lawrence