[petsc-users] Problem with DMRefine and DMLabel

[Santos Teixeira Frederico]

Hi Matt,

Thanks for your explanation.

The option -dm_refine worked for me because I could keep the effect of -dm_plex_separate_marker. I playing with Neumann and Dirichlet boundaries to solve the Poiseulle flow, so I need different ids.

The function DMPlexMarkBoundaryFace would set all the points with the same id, right?

Regards,
 Fred.


________________________________
From: Matthew Knepley [knepley at gmail.com]
Sent: 13 December 2017 12:15
To: Santos Teixeira Frederico
Cc: petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] Problem with DMRefine and DMLabel

On Wed, Dec 13, 2017 at 4:30 AM, Santos Teixeira Frederico <fsantost at student.ethz.ch<mailto:fsantost at student.ethz.ch>> wrote:
Hi folks,

In the example SNES/62.c, when I use "-simplex 1" and "-refinement_limit 0.05", it seems the refined DMPlex does not carry all the labels from the original DM.

This is correct. Here is the problem. When you use -refinement_limit (instead of -dm_refine), I call Triangle/TetGen to do
the refinement. They do not tell me how they changed the mesh to get there, so I have no way of propagating the labels.
There is a special name ("marker") that I was using for the boundary, which I automatically mark after generation.

We could choose to also mark boundary faces, but it seems redundant. If you want them marked, you can call
DMPlexMarkBoundaryFaces() on the new mesh. Does this seem reasonable?

  Thanks,

      Matt

You can see that if you place, in the function CreateMesh, one DMViewFromOptions right after the DMPlexCreateBoxMesh and another DMViewFromOptions after DMRefine. The first output is

DM Object: DM_0x84000000_0 1 MPI processes
  type: plex
DM_0x84000000_0 in 2 dimensions:
  0-cells: 9
  1-cells: 16
  2-cells: 8
Labels:
  Face Sets: 4 strata with value/size (1 (2), 4 (2), 2 (2), 3 (2))
  marker: 4 strata with value/size (4 (5), 1 (3), 2 (5), 3 (3))
  depth: 3 strata with value/size (0 (9), 1 (16), 2 (8))

which is correct w.r.t. the definition from DMPlexCreateBoxMesh. However, the second output is

DM Object: DM_0x84000000_1 1 MPI processes
  type: plex
DM_0x84000000_1 in 2 dimensions:
  0-cells: 145
  1-cells: 400
  2-cells: 256
Labels:
  marker: 4 strata with value/size (4 (3), 1 (57), 2 (3), 3 (1))
  depth: 3 strata with value/size (0 (145), 1 (400), 2 (256))

Note that the label "Face Sets" disappeared and that the label "marker" does not include all the boundary points.
The full set of options is:

-run_type full
-refinement_limit 0.005
-simplex 1
-dm_view
-dm_plex_separate_marker
-interpolate 1
-vel_petscspace_order 2
-pres_petscspace_order 1
-ksp_view
-ksp_monitor
-ksp_type fgmres
-ksp_gmres_restart 10
-ksp_rtol 1.0e-9
-pc_type fieldsplit
-pc_fieldsplit_type schur
-pc_fieldsplit_schur_factorization_type full
-fieldsplit_pressure_ksp_rtol 1e-10
-fieldsplit_velocity_ksp_type gmres
-fieldsplit_velocity_pc_type lu
-fieldsplit_pressure_pc_type jacobi
-snes_error_if_not_converged
-ksp_error_if_not_converged
-snes_view
-snes_monitor

Am I missing anything?

Regards,
 Fred.



--
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.caam.rice.edu/~mk51/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20171213/c53f4155/attachment-0001.html>