Date: 2025-03-29T05:58:52+00:00

Actual source code: ex4.c

      1: static char help[] = "Demonstrates using ISLocalToGlobalMappings.\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(ISLocalToGlobalMappingCreate(PETSC_COMM_WORLD, 1, n, indices, PETSC_COPY_VALUES, &mapping));
     20:   PetscCall(ISLocalToGlobalMappingSetFromOptions(mapping));

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

     28:   /*
     29:      Map some global indices to local, retaining the ones without a local index by -1
     30:   */
     31:   for (i = 0; i < 13; i++) inglobals[i] = i;
     32:   PetscCall(ISGlobalToLocalMappingApply(mapping, IS_GTOLM_MASK, 13, inglobals, NULL, outlocals));
     33:   PetscCall(PetscIntView(13, outlocals, PETSC_VIEWER_STDOUT_WORLD));

     35:   /*
     36:      Map some global indices to local, dropping the ones without a local index.
     37:   */
     38:   PetscCall(ISGlobalToLocalMappingApply(mapping, IS_GTOLM_DROP, 13, inglobals, &m, outlocals));
     39:   PetscCall(PetscIntView(m, outlocals, PETSC_VIEWER_STDOUT_WORLD));

     41:   PetscCall(ISLocalToGlobalMappingView(mapping, PETSC_VIEWER_STDOUT_WORLD));
     42:   /*
     43:      Free the space used by the local to global mapping
     44:   */
     45:   PetscCall(ISLocalToGlobalMappingDestroy(&mapping));

     47:   PetscCall(PetscFinalize());
     48:   return 0;
     49: }

     51: /*TEST

     53:    test:

     55:    test:
     56:       suffix: 2
     57:       args: -islocaltoglobalmapping_type hash

     59: TEST*/