On Mon 10. Feb 2020 at 13:09, Matthew Knepley <knep...@gmail.com> wrote:
> On Sun, Feb 9, 2020 at 11:11 PM Pierre Jolivet <pierre.joli...@enseeiht.fr> > wrote: > >> >> >> On 10 Feb 2020, at 6:20 AM, Matthew Knepley <knep...@gmail.com> wrote: >> >> On Sun, Feb 9, 2020 at 3:23 PM Pierre Jolivet <pierre.joli...@enseeiht.fr> >> wrote: >> >>> 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 >>> […] >>> >> >> It looks like your fine grid has no discretization, since 0 is >> numFIndices from >> >> ierr = DMPlexGetClosureIndices(dmf, fsection, globalFSection, cell, >> &numFIndices, &findices, NULL);CHKERRQ(ierr); >> >> >>> [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) >>> >> >> I don't think its broken. >> >> >> Oh, OK. Could you help me figure out what’s the problem then, e.g., with >> a slight (command line) variation of test #6, please? >> > > Sure. I am at SIAM this week, but as soon as I can I will get you the fix. > > >> $ cd src/dm/impls/plex/examples/tests >> $ git diff ex19.c >> $ make ex19 >> $ mpirun ./ex19 -dim 3 -nbrVerEdge 10 -dm_plex_separate_marker 0 -met 0 >> -hmin 0.1 -hmax 0.3 -init_dm_view -adapt_dm_view -do_L2 -petscspace_degree >> 1 -petscfe_default_quadrature_order 1 -dm_plex_hash_location >> [0]PETSC ERROR: Nonconforming object sizes >> [0]PETSC ERROR: The section point closure size 0 != dual space dimension 4 >> […] >> [0]PETSC ERROR: #1 DMProjectLocal_Generic_Plex() line 633 in >> src/dm/impls/plex/plexproject.c >> [0]PETSC ERROR: #2 DMProjectFunctionLocal_Plex() line 771 in >> src/dm/impls/plex/plexproject.c >> [0]PETSC ERROR: #3 DMProjectFunctionLocal() line 7809 in >> src/dm/interface/dm.c >> [0]PETSC ERROR: #4 DMProjectFunction() line 7766 in src/dm/interface/dm.c >> >> If I comment the DMProjectFunction() call, I end up with the same error >> as in my first message in DMCreateInterpolation(). >> >> 2) is DMCreateInterpolation + MatInterpolate the correct way of >>> transferring one Vec from a DMPlex onto another? >>> >> >> That is the intent. >> >> >>> 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. >>> >> >> In general, it is going to be horrible. Here is what it does: locate the >> fine quadrature points in the coarse grid and interpolate to them. This >> quadrature can have huge errors if it falls across multiple cells. This is >> why the nested version works perfectly, and also why Patrick Farrell and >> James Maddison have the Supermesh library, which makes a refinement of the >> mesh until the quadrature is accurate everywhere. That way they guarantee >> that at least the zeroth moment is preserved. >> >> >> Two subquestions if I may: >> 1) are there any plans to have this integrated through an external >> package? >> > > In the absence of a plan, there is a hope. I would really like it to > happen. > > >> 2) if I understand you correctly, you answered about the numerical >> performance of the function. I can live with high interpolation errors if >> both meshes are “far" from each other. I was mostly interested in the >> parallel performance of the function. >> > > Everything is purely local except for point location. Since it has never > really been tested in this mode, I am sure the > scaling can be bad. I believe the default is to extrapolate if the point > is not covered, which makes sense for mostly > matching meshes. There is parallel point location, but it is intended for > a few points where we are sampling the solution, > rather than lots of points everywhere which you would get for non-matching > meshes with different distributions. Could > you say what kind of situation you are trying to optimize for? > Matt, probably clarifying the parallel point location algorithm is helpful. 1/ Does it broadcast all off rank points to every rank? Or 2/ Does it broadcast sub domain bounding boxes to every rank, and then scatter points to candidate owning ranks based on the bounding boxes containing off rank points? I recall the method (years ago) did what’s described in (1) > Thanks, > > Matt > > >> Thanks, >> Pierre >> >> Thanks, >> >> Matt >> >> >>> 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)) >>> >>> >>> >> >> -- >> 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/> >> >> >> > > -- > 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/> >