[petsc-users] realCoords for DOFs

[Mark Adams]

PETSc does not store the coordinates for high order elements (ie, the
"midside nodes").
I get them by projecting a f(x) = x, function.
Not sure if that is what you want but I can give you a code snippet if
there are no better ideas.

Mark


On Mon, Dec 12, 2022 at 6:06 PM Yann Jobic <yann.jobic at univ-amu.fr> wrote:

> Hi all,
>
> I'm trying to get the coords of the dofs of a DMPlex for a PetscFE
> discretization, for orders greater than 1.
>
> I'm struggling to run dm/impls/plex/tutorials/ex8.c
> I've got the following error (with option -view_coord) :
>
> [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> [0]PETSC ERROR: Object is in wrong state
> [0]PETSC ERROR: DMGetCoordinatesLocalSetUp() has not been called
> [0]PETSC ERROR: See https://petsc.org/release/faq/ for trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.18.2, unknown
> [0]PETSC ERROR:
> /home/jobic/projet/fe-utils/petsc/fetools/cmake-build-debug/ex_closure_petsc
>
> on a  named luke by jobic Mon Dec 12 23:34:37 2022
> [0]PETSC ERROR: Configure options
> --prefix=/local/lib/petsc/3.18/p3/gcc/nompi_hdf5 --with-mpi=0
> --with-debugging=1 --with-blacs=1 --download-zlib,--download-p4est
> --download-hdf5=1 --download-triangle=1 --with-single-library=0
> --with-large-file-io=1 --with-shared-libraries=0 -CFLAGS=" -g -O0"
> -CXXFLAGS=" -g -O0" -FFLAGS=" -g -O0" PETSC_ARCH=nompi_gcc_hdf5
> [0]PETSC ERROR: #1 DMGetCoordinatesLocalNoncollective() at
> /home/devel/src_linux/petsc-3.18.0/src/dm/interface/dmcoordinates.c:621
> [0]PETSC ERROR: #2 DMPlexGetCellCoordinates() at
> /home/devel/src_linux/petsc-3.18.0/src/dm/impls/plex/plexgeometry.c:1291
> [0]PETSC ERROR: #3 main() at
> /home/jobic/projet/fe-utils/petsc/fetools/src/ex_closure_petsc.c:86
> [0]PETSC ERROR: PETSc Option Table entries:
> [0]PETSC ERROR: -dm_plex_box_faces 2,2
> [0]PETSC ERROR: -dm_plex_dim 2
> [0]PETSC ERROR: -dm_plex_simplex 0
> [0]PETSC ERROR: -petscspace_degree 1
> [0]PETSC ERROR: -view_coord
> [0]PETSC ERROR: ----------------End of Error Message -------send entire
> error message to petsc-maint at mcs.anl.gov----------
>
> Maybe i've done something wrong ?
>
>
> Moreover, i don't quite understand the function DMPlexGetLocalOffsets,
> and how to use it with DMGetCoordinatesLocal. It seems that
> DMGetCoordinatesLocal do not have the coords of the dofs, but only the
> nodes defining the geometry.
>
> I've made some small modifications of ex8.c, but i still have an error :
> [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> [0]PETSC ERROR: Invalid argument
> [0]PETSC ERROR: Wrong type of object: Parameter # 1
> [0]PETSC ERROR: WARNING! There are option(s) set that were not used!
> Could be the program crashed before they were used or a spelling
> mistake, etc!
> [0]PETSC ERROR: Option left: name:-sol value: vtk:sol.vtu
> [0]PETSC ERROR: See https://petsc.org/release/faq/ for trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.18.2, unknown
> [0]PETSC ERROR:
> /home/jobic/projet/fe-utils/petsc/fetools/cmake-build-debug/view_coords
> on a  named luke by jobic Mon Dec 12 23:51:05 2022
> [0]PETSC ERROR: Configure options
> --prefix=/local/lib/petsc/3.18/p3/gcc/nompi_hdf5 --with-mpi=0
> --with-debugging=1 --with-blacs=1 --download-zlib,--download-p4est
> --download-hdf5=1 --download-triangle=1 --with-single-library=0
> --with-large-file-io=1 --with-shared-libraries=0 -CFLAGS=" -g -O0"
> -CXXFLAGS=" -g -O0" -FFLAGS=" -g -O0" PETSC_ARCH=nompi_gcc_hdf5
> [0]PETSC ERROR: #1 PetscFEGetHeightSubspace() at
> /home/devel/src_linux/petsc-3.18.0/src/dm/dt/fe/interface/fe.c:1692
> [0]PETSC ERROR: #2 DMPlexGetLocalOffsets() at
> /home/devel/src_linux/petsc-3.18.0/src/dm/impls/plex/plexceed.c:98
> [0]PETSC ERROR: #3 ViewOffsets() at
> /home/jobic/projet/fe-utils/petsc/fetools/src/view_coords.c:28
> [0]PETSC ERROR: #4 main() at
> /home/jobic/projet/fe-utils/petsc/fetools/src/view_coords.c:99
> [0]PETSC ERROR: PETSc Option Table entries:
> [0]PETSC ERROR: -heat_petscspace_degree 2
> [0]PETSC ERROR: -sol vtk:sol.vtu
> [0]PETSC ERROR: ----------------End of Error Message -------send entire
> error message to petsc-maint at mcs.anl.gov----------
>
>
> Is dm/impls/plex/tutorials/ex8.c a good example for viewing the coords
> of the dofs of a DMPlex ?
>
>
> Thanks,
>
> Yann
>
>
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