Actual source code: ex1.c


  2: static char help[] = "Creating a general index set.\n\n";

  4: /*
  5:     Include petscis.h so we can use PETSc IS objects. Note that this automatically
  6:   includes petscsys.h.
  7: */
  8: #include <petscis.h>
  9: #include <petscviewer.h>

 11: int main(int argc,char **argv)
 12: {
 13:   PetscInt       *indices,n;
 14:   const PetscInt *nindices;
 15:   PetscMPIInt    rank;
 16:   IS             is;

 18:   PetscInitialize(&argc,&argv,(char*)0,help);
 19:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);

 21:   /*
 22:      Create an index set with 5 entries. Each processor creates
 23:    its own index set with its own list of integers.
 24:   */
 25:   PetscMalloc1(5,&indices);
 26:   indices[0] = rank + 1;
 27:   indices[1] = rank + 2;
 28:   indices[2] = rank + 3;
 29:   indices[3] = rank + 4;
 30:   indices[4] = rank + 5;
 31:   ISCreateGeneral(PETSC_COMM_SELF,5,indices,PETSC_COPY_VALUES,&is);
 32:   /*
 33:      Note that ISCreateGeneral() has made a copy of the indices
 34:      so we may (and generally should) free indices[]
 35:   */
 36:   PetscFree(indices);

 38:   /*
 39:      Print the index set to stdout
 40:   */
 41:   ISView(is,PETSC_VIEWER_STDOUT_SELF);

 43:   /*
 44:      Get the number of indices in the set
 45:   */
 46:   ISGetLocalSize(is,&n);

 48:   /*
 49:      Get the indices in the index set
 50:   */
 51:   ISGetIndices(is,&nindices);
 52:   /*
 53:      Now any code that needs access to the list of integers
 54:    has access to it here through indices[].
 55:    */
 56:   PetscPrintf(PETSC_COMM_SELF,"[%d] First index %" PetscInt_FMT "\n",rank,nindices[0]);

 58:   /*
 59:      Once we no longer need access to the indices they should
 60:      returned to the system
 61:   */
 62:   ISRestoreIndices(is,&nindices);

 64:   /*
 65:      One should destroy any PETSc object once one is completely
 66:     done with it.
 67:   */
 68:   ISDestroy(&is);
 69:   PetscFinalize();
 70:   return 0;
 71: }

 73: /*TEST

 75:    test:

 77: TEST*/