Date: 2022-03-04T17:38:30+00:00

Actual source code: ex1.c

      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:   PetscViewer    viewer;
     11:   PetscInt       dim, numFields, numBC, i;
     12:   PetscInt       numComp[3];
     13:   PetscInt       numDof[12];
     14:   PetscInt       bcField[1];
     15:   IS             bcPointIS[1];

     18:   PetscInitialize(&argc, &argv, NULL,help);if (ierr) return ierr;
     19:   /* Create a mesh */
     20:   DMCreate(PETSC_COMM_WORLD, &dm);
     21:   DMSetType(dm, DMPLEX);
     22:   DMSetFromOptions(dm);
     23:   DMViewFromOptions(dm, NULL, "-dm_view");
     24:   DMGetDimension(dm, &dim);
     25:   /* Create a scalar field u, a vector field v, and a surface vector field w */
     26:   numFields  = 3;
     27:   numComp[0] = 1;
     28:   numComp[1] = dim;
     29:   numComp[2] = dim-1;
     30:   for (i = 0; i < numFields*(dim+1); ++i) numDof[i] = 0;
     31:   /* Let u be defined on vertices */
     32:   numDof[0*(dim+1)+0]     = 1;
     33:   /* Let v be defined on cells */
     34:   numDof[1*(dim+1)+dim]   = dim;
     35:   /* Let w be defined on faces */
     36:   numDof[2*(dim+1)+dim-1] = dim-1;
     37:   /* Setup boundary conditions */
     38:   numBC = 1;
     39:   /* Prescribe a Dirichlet condition on u on the boundary
     40:        Label "marker" is made by the mesh creation routine */
     41:   bcField[0] = 0;
     42:   DMGetStratumIS(dm, "marker", 1, &bcPointIS[0]);
     43:   /* Create a PetscSection with this data layout */
     44:   DMSetNumFields(dm, numFields);
     45:   DMPlexCreateSection(dm, NULL, numComp, numDof, numBC, bcField, NULL, bcPointIS, NULL, &section);
     46:   ISDestroy(&bcPointIS[0]);
     47:   /* Name the Field variables */
     48:   PetscSectionSetFieldName(section, 0, "u");
     49:   PetscSectionSetFieldName(section, 1, "v");
     50:   PetscSectionSetFieldName(section, 2, "w");
     51:   PetscSectionView(section, PETSC_VIEWER_STDOUT_WORLD);
     52:   /* Tell the DM to use this data layout */
     53:   DMSetLocalSection(dm, section);
     54:   /* Create a Vec with this layout and view it */
     55:   DMGetGlobalVector(dm, &u);
     56:   PetscViewerCreate(PETSC_COMM_WORLD, &viewer);
     57:   PetscViewerSetType(viewer, PETSCVIEWERVTK);
     58:   PetscViewerFileSetName(viewer, "sol.vtu");
     59:   VecView(u, viewer);
     60:   PetscViewerDestroy(&viewer);
     61:   DMRestoreGlobalVector(dm, &u);
     62:   /* Cleanup */
     63:   PetscSectionDestroy(&section);
     64:   DMDestroy(&dm);
     65:   PetscFinalize();
     66:   return ierr;
     67: }

     69: /*TEST

     71:   test:
     72:     suffix: 0
     73:     requires: triangle
     74:     args: -info :~sys,mat
     75:   test:
     76:     suffix: 1
     77:     requires: ctetgen
     78:     args: -dm_plex_dim 3 -info :~sys,mat

     80: TEST*/