[petsc-users] DMPlex periodic face coordinates

[Matteo Semplice]

Dear petsc-users,

     I am playing with DMPlexGetCellCoordinates and observing that it 
returns correct periodic coordinates for cells, but not for faces.

More precisely, adding

PetscCall(DMPlexGetHeightStratum(dm, 1, &fStart, &fEnd));
     for (f = fStart; f < fEnd; ++f) {
       const PetscScalar *array;
       PetscScalar       *x = NULL;
       PetscInt           ndof;
       PetscBool          isDG;

       PetscCall(DMPlexGetCellCoordinates(dm, f, &isDG, &ndof, &array, &x));
       PetscCheck(ndof % cdim == 0, PETSC_COMM_SELF, 
PETSC_ERR_ARG_INCOMP, "ndof not divisible by cdim");
       PetscCall(PetscPrintf(PETSC_COMM_SELF, "Face #%" PetscInt_FMT " 
coordinates\n", f - fStart));
       for (PetscInt i = 0; i < ndof; i += cdim) 
PetscCall(PetscScalarView(cdim, &x[i], PETSC_VIEWER_STDOUT_SELF));
       PetscCall(DMPlexRestoreCellCoordinates(dm, f, &isDG, &ndof, 
&array, &x));
     }

to src/dm/impls/plex/tutorials/ex8.c, I get

$ ./ex8 -dm_plex_dim 2 -petscspace_degree 1 -dm_plex_simplex 0 
-dm_plex_box_faces 3,2 -dm_plex_box_bd periodic,none -dm_view -view_coord
DM Object: box 1 MPI process
   type: plex
box in 2 dimensions:
   Number of 0-cells per rank: 9
   Number of 1-cells per rank: 15
   Number of 2-cells per rank: 6
Periodic mesh (PERIODIC, NONE) coordinates localized

[...]

Element #2 coordinates
  0:   6.6667e-01   0.0000e+00
  0:   1.0000e+00   0.0000e+00 <<<----- correct
  0:   1.0000e+00   5.0000e-01
  0:   6.6667e-01   5.0000e-01
[...]

Face #0 coordinates
  0:   0.0000e+00   0.0000e+00
  0:   3.3333e-01   0.0000e+00
Face #1 coordinates
  0:   3.3333e-01   0.0000e+00
  0:   6.6667e-01   0.0000e+00
Face #2 coordinates
  0:   6.6667e-01   0.0000e+00
  0:   0.0000e+00   0.0000e+00  <<<---- should be (0.66,0.00) and 
(1.00,0.00)

Is there a way to recover correct periodic coordinates in the case of 
periodic DMPLex?

Thanks in advance

Matteo
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