2: static char help[] = "Demonstrates using ISLocalToGlobalMappings.\n\n";

  4: /*T
  5:     Concepts: local to global mappings
  6:     Concepts: global to local mappings

  8:     Description:  Creates an index set based on blocks of integers. Views that index set
  9:     and then destroys it.
 10: T*/

 12: #include <petscis.h>
 13: #include <petscviewer.h>

 17: int main(int argc,char **argv)
 18: {
 19:   PetscErrorCode         ierr;
 20:   PetscInt               i,n = 4,indices[] = {0,3,9,12},m = 2,input[] = {0,2};
 21:   PetscInt               output[2],inglobals[13],outlocals[13];
 22:   ISLocalToGlobalMapping mapping;

 24:   PetscInitialize(&argc,&argv,(char*)0,help);

 26:   /*
 27:       Create a local to global mapping. Each processor independently
 28:      creates a mapping
 29:   */
 30:   ISLocalToGlobalMappingCreate(PETSC_COMM_WORLD,1,n,indices,PETSC_COPY_VALUES,&mapping);

 32:   /*
 33:      Map a set of local indices to their global values
 34:   */
 35:   ISLocalToGlobalMappingApply(mapping,m,input,output);
 36:   PetscIntView(m,output,PETSC_VIEWER_STDOUT_WORLD);

 38:   /*
 39:      Map some global indices to local, retaining the ones without a local index by -1
 40:   */
 41:   for (i=0; i<13; i++) inglobals[i] = i;
 42:   ISGlobalToLocalMappingApply(mapping,IS_GTOLM_MASK,13,inglobals,NULL,outlocals);
 43:   PetscIntView(13,outlocals,PETSC_VIEWER_STDOUT_WORLD);

 45:   /*
 46:      Map some global indices to local, dropping the ones without a local index.
 47:   */
 48:   ISGlobalToLocalMappingApply(mapping,IS_GTOLM_DROP,13,inglobals,&m,outlocals);
 49:   PetscIntView(m,outlocals,PETSC_VIEWER_STDOUT_WORLD);

 51:   /*
 52:      Free the space used by the local to global mapping
 53:   */
 54:   ISLocalToGlobalMappingDestroy(&mapping);


 57:   PetscFinalize();
 58:   return 0;
 59: }