1: static char help[] = "Define a simple field over the mesh\n\n";

  3: #include <petscdmplex.h>

  5: int main(int argc, char **argv)
  6: {
  7:   DM           dm;
  8:   Vec          u;
  9:   PetscSection section;
 10:   PetscInt     dim, numFields, numBC;
 11:   PetscInt     numComp[3];
 12:   PetscInt     numDof[12];
 13:   PetscInt     bcField[1];
 14:   IS           bcPointIS[1];

 16:   PetscFunctionBeginUser;
 17:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));
 18:   /* Create a mesh */
 19:   PetscCall(DMCreate(PETSC_COMM_WORLD, &dm));
 20:   PetscCall(DMSetType(dm, DMPLEX));
 21:   PetscCall(DMSetFromOptions(dm));
 22:   PetscCall(DMViewFromOptions(dm, NULL, "-dm_view"));
 23:   PetscCall(DMGetDimension(dm, &dim));
 24:   /* Create a scalar field u, a vector field v, and a surface vector field w */
 25:   numFields  = 3;
 26:   numComp[0] = 1;
 27:   numComp[1] = dim;
 28:   numComp[2] = dim - 1;
 29:   for (PetscInt i = 0; i < numFields * (dim + 1); ++i) numDof[i] = 0;
 30:   /* Let u be defined on vertices */
 31:   numDof[0 * (dim + 1) + 0] = 1;
 32:   /* Let v be defined on cells */
 33:   numDof[1 * (dim + 1) + dim] = dim;
 34:   /* Let w be defined on faces */
 35:   numDof[2 * (dim + 1) + dim - 1] = dim - 1;
 36:   /* Setup boundary conditions */
 37:   numBC = 1;
 38:   /* Prescribe a Dirichlet condition on u on the boundary
 39:        Label "marker" is made by the mesh creation routine */
 40:   bcField[0] = 0;
 41:   PetscCall(DMGetStratumIS(dm, "marker", 1, &bcPointIS[0]));
 42:   /* Create a PetscSection with this data layout */
 43:   PetscCall(DMSetNumFields(dm, numFields));
 44:   PetscCall(DMPlexCreateSection(dm, NULL, numComp, numDof, numBC, bcField, NULL, bcPointIS, NULL, &section));
 45:   PetscCall(ISDestroy(&bcPointIS[0]));
 46:   /* Name the Field variables */
 47:   PetscCall(PetscSectionSetFieldName(section, 0, "u"));
 48:   PetscCall(PetscSectionSetFieldName(section, 1, "v"));
 49:   PetscCall(PetscSectionSetFieldName(section, 2, "w"));
 50:   PetscCall(PetscSectionViewFromOptions(section, NULL, "-mysection_view"));
 51:   /* Tell the DM to use this data layout */
 52:   PetscCall(DMSetLocalSection(dm, section));
 53:   /* Create a Vec with this layout and view it */
 54:   PetscCall(DMGetGlobalVector(dm, &u));
 55:   PetscCall(PetscObjectSetName((PetscObject)u, "Solution"));
 56:   PetscCall(VecSet(u, 1.));
 57:   PetscCall(VecViewFromOptions(u, NULL, "-vec_view"));
 58:   PetscCall(DMRestoreGlobalVector(dm, &u));
 59:   /* Cleanup */
 60:   PetscCall(PetscSectionDestroy(&section));
 61:   PetscCall(DMDestroy(&dm));
 62:   PetscCall(PetscFinalize());
 63:   return 0;
 64: }

 66: /*TEST

 68:   test:
 69:     suffix: 0
 70:     requires: triangle
 71:     args: -mysection_view -vec_view vtk:sol.vtu -info :~sys,mat

 73:   test:
 74:     suffix: 1
 75:     requires: ctetgen
 76:     args: -dm_plex_dim 3 -mysection_view -info :~sys,mat

 78:   test:
 79:     suffix: filter_0
 80:     args: -dm_plex_simplex 0 -dm_plex_box_faces 3,3 -dm_plex_label_lower 0,1,2,3,4,6 \
 81:       -dm_refine 1 -dm_plex_transform_type transform_filter -dm_plex_transform_active lower \
 82:       -dm_view

 84:   test:
 85:     suffix: submesh_0
 86:     requires: triangle
 87:     args: -dm_plex_label_middle 9,12,15,23,31 -dm_plex_submesh middle -dm_view

 89: TEST*/