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>

 15: int main(int argc,char **argv)
 16: {
 17:   PetscErrorCode         ierr;
 18:   PetscInt               i,n = 4,indices[] = {0,3,9,12},m = 2,input[] = {0,2};
 19:   PetscInt               output[2],inglobals[13],outlocals[13];
 20:   ISLocalToGlobalMapping mapping;

 22:   PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;

 24:   /*
 25:       Create a local to global mapping. Each processor independently
 26:      creates a mapping
 27:   */
 28:   ISLocalToGlobalMappingCreate(PETSC_COMM_WORLD,1,n,indices,PETSC_COPY_VALUES,&mapping);
 29:   ISLocalToGlobalMappingSetFromOptions(mapping);

 31:   /*
 32:      Map a set of local indices to their global values
 33:   */
 34:   ISLocalToGlobalMappingApply(mapping,m,input,output);
 35:   PetscIntView(m,output,PETSC_VIEWER_STDOUT_WORLD);

 37:   /*
 38:      Map some global indices to local, retaining the ones without a local index by -1
 39:   */
 40:   for (i=0; i<13; i++) inglobals[i] = i;
 41:   ISGlobalToLocalMappingApply(mapping,IS_GTOLM_MASK,13,inglobals,NULL,outlocals);
 42:   PetscIntView(13,outlocals,PETSC_VIEWER_STDOUT_WORLD);

 44:   /*
 45:      Map some global indices to local, dropping the ones without a local index.
 46:   */
 47:   ISGlobalToLocalMappingApply(mapping,IS_GTOLM_DROP,13,inglobals,&m,outlocals);
 48:   PetscIntView(m,outlocals,PETSC_VIEWER_STDOUT_WORLD);

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


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