Date: 2026-03-31T05:46:38+00:00

Actual source code: ex5.c

      1: static char help[] = "Demonstrates using ISLocalToGlobalMappings with block size.\n\n";

      3: #include <petscis.h>
      4: #include <petscviewer.h>

      6: int main(int argc, char **argv)
      7: {
      8:   PetscInt               i, n = 4, indices[] = {0, 3, 9, 12}, m = 2, input[] = {0, 2};
      9:   PetscInt               output[2], inglobals[13], outlocals[13];
     10:   ISLocalToGlobalMapping mapping;

     12:   PetscFunctionBeginUser;
     13:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));

     15:   /*
     16:       Create a local to global mapping. Each processor independently
     17:      creates a mapping
     18:   */
     19:   PetscCall(PetscIntView(n, indices, PETSC_VIEWER_STDOUT_WORLD));
     20:   PetscCall(ISLocalToGlobalMappingCreate(PETSC_COMM_WORLD, 2, n, indices, PETSC_COPY_VALUES, &mapping));

     22:   /*
     23:      Map a set of local indices to their global values
     24:   */
     25:   PetscCall(PetscIntView(m, input, PETSC_VIEWER_STDOUT_WORLD));
     26:   PetscCall(ISLocalToGlobalMappingApply(mapping, m, input, output));
     27:   PetscCall(PetscIntView(m, output, PETSC_VIEWER_STDOUT_WORLD));

     29:   /*
     30:      Map some global indices to local, retaining the ones without a local index by -1
     31:   */
     32:   for (i = 0; i < 13; i++) inglobals[i] = i;
     33:   PetscCall(PetscIntView(13, inglobals, PETSC_VIEWER_STDOUT_WORLD));
     34:   PetscCall(ISGlobalToLocalMappingApply(mapping, IS_GTOLM_MASK, 13, inglobals, NULL, outlocals));
     35:   PetscCall(PetscIntView(13, outlocals, PETSC_VIEWER_STDOUT_WORLD));

     37:   /*
     38:      Map some block global indices to local, dropping the ones without a local index.
     39:   */
     40:   PetscCall(PetscIntView(13, inglobals, PETSC_VIEWER_STDOUT_WORLD));
     41:   PetscCall(ISGlobalToLocalMappingApplyBlock(mapping, IS_GTOLM_DROP, 13, inglobals, &m, outlocals));
     42:   PetscCall(PetscIntView(m, outlocals, PETSC_VIEWER_STDOUT_WORLD));

     44:   /*
     45:      Free the space used by the local to global mapping
     46:   */
     47:   PetscCall(ISLocalToGlobalMappingDestroy(&mapping));

     49:   PetscCall(PetscFinalize());
     50:   return 0;
     51: }

     53: /*TEST

     55:    test:

     57: TEST*/