1: /*$Id: ex1.c,v 1.27 2001/03/23 23:21:14 balay Exp $*/

  3: static char help[] = "Creating a general index set.nn";

  5: /*T
  6:     Concepts: index sets^manipulating a general index set;
  7:     Concepts: index sets^creating general;
  8:     Concepts: IS^creating a general index set;

 10:     Description: Creates an index set based on a set of integers. Views that index set
 11:     and then destroys it.
 12:     
 13: T*/
 14: 
 15: /*
 16:     Include petscis.h so we can use PETSc IS objects. Note that this automatically 
 17:   includes petsc.h.
 18: */
 19:  #include petscis.h

 21: #undef __FUNCT__
 23: int main(int argc,char **argv)
 24: {
 25:   int      ierr,*indices,rank,n;
 26:   IS       is;

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

 31:   /*
 32:      Create an index set with 5 entries. Each processor creates
 33:    its own index set with its own list of integers.
 34:   */
 35:   PetscMalloc(5*sizeof(int),&indices);
 36:   indices[0] = rank + 1;
 37:   indices[1] = rank + 2;
 38:   indices[2] = rank + 3;
 39:   indices[3] = rank + 4;
 40:   indices[4] = rank + 5;
 41:   ISCreateGeneral(PETSC_COMM_SELF,5,indices,&is);
 42:   /*
 43:      Note that ISCreateGeneral() has made a copy of the indices
 44:      so we may (and generally should) free indices[]
 45:   */
 46:   PetscFree(indices);

 48:   /*
 49:      Print the index set to stdout
 50:   */
 51:   ISView(is,PETSC_VIEWER_STDOUT_SELF);

 53:   /*
 54:      Get the number of indices in the set 
 55:   */
 56:   ISGetLocalSize(is,&n);

 58:   /*
 59:      Get the indices in the index set
 60:   */
 61:   ISGetIndices(is,&indices);
 62:   /*
 63:      Now any code that needs access to the list of integers
 64:    has access to it here through indices[].
 65:    */
 66:   PetscPrintf(PETSC_COMM_SELF,"[%d] First index %dn",rank,indices[0]);

 68:   /*
 69:      Once we no longer need access to the indices they should 
 70:      returned to the system 
 71:   */
 72:   ISRestoreIndices(is,&indices);

 74:   /*
 75:      One should destroy any PETSc object once one is completely
 76:     done with it.
 77:   */
 78:   ISDestroy(is);
 79:   PetscFinalize();
 80:   return 0;
 81: }
 82: