[petsc-dev] DMPlex + P_1 FE interpolation

[Pierre Jolivet]

Hello,
I’ve a hard time answering the following DMPlex questions by just looking at some of the examples and manual.
Considering two DMPlex dm and dma, as in petsc/src/dm/impls/plex/examples/tests/ex19.c, I’d like to interpolate a simple P_1 FE function from dm to dma.
The DMCreateInterpolation call gives me:
[0]PETSC ERROR: Invalid argument
[0]PETSC ERROR: Number of fine indices 0 != 4 dual basis vecs
[…]
[0]PETSC ERROR: #1 DMPlexComputeInterpolatorGeneral() line 2508 in petsc/src/dm/impls/plex/plexfem.c
[0]PETSC ERROR: #2 DMCreateInterpolation_Plex() line 7688 in petsc/src/dm/impls/plex/plex.c
[0]PETSC ERROR: #3 DMCreateInterpolation() line 1139 in petsc/src/dm/interface/dm.c
But the DMs look OK, don’t they, cf. below?
So I have three simple questions:
1) are all tests at the bottom of ex19.c broken because of PRAgMaTIc or because of DMPlex currently not supporting some operations? (I’m not using PRAgMaTIc to do mesh adaptation, so I was hoping to not run into an error)
2) is DMCreateInterpolation + MatInterpolate the correct way of transferring one Vec from a DMPlex onto another?
3) if yes, by looking at the names of the arguments in DMPlexComputeInterpolatorGeneral, dmc and dmf, could you comment on the performance of this function for unrelated meshes, e.g., if both DMs are “fine” and not one coarse and the other fine (albeit non-nested), for simple P_k spaces.

Thanks in advance for your help,
Pierre

$ mpirun -n 1 ./ex19 -msh in.msh -init_dm_view ::ascii_info -adapt_dm_view ::ascii_info -mat_view ::ascii_info -do_L2 -petscspace_degree 1
DM Object: DMinit 1 MPI processes
  type: plex
DMinit in 3 dimensions:
  0-cells: 1331
  1-cells: 7930
  2-cells: 12600
  3-cells: 6000
Labels:
  depth: 4 strata with value/size (0 (1331), 1 (7930), 2 (12600), 3 (6000))
  Face Sets: 6 strata with value/size (4 (200), 1 (200), 5 (200), 2 (200), 3 (200), 6 (200))
  Cell Sets: 1 strata with value/size (0 (6000))
DM Object: DMadapt (adapt_) 1 MPI processes
  type: plex
DMadapt in 3 dimensions:
  0-cells: 2905
  1-cells: 18888
  2-cells: 31368
  3-cells: 15384
Labels:
  depth: 4 strata with value/size (0 (2905), 1 (18888), 2 (31368), 3 (15384))
  Face Sets: 6 strata with value/size (1 (200), 4 (200), 6 (200), 2 (200), 5 (200), 3 (200))
  Cell Sets: 1 strata with value/size (0 (15384))