Actual source code: ex1.c

  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: int main(int argc,char **argv)
 22: {
 23:   int      ierr,*indices,rank,n;
 24:   IS       is;

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

 29:   /*
 30:      Create an index set with 5 entries. Each processor creates
 31:    its own index set with its own list of integers.
 32:   */
 33:   PetscMalloc(5*sizeof(int),&indices);
 34:   indices[0] = rank + 1;
 35:   indices[1] = rank + 2;
 36:   indices[2] = rank + 3;
 37:   indices[3] = rank + 4;
 38:   indices[4] = rank + 5;
 39:   ISCreateGeneral(PETSC_COMM_SELF,5,indices,&is);
 40:   /*
 41:      Note that ISCreateGeneral() has made a copy of the indices
 42:      so we may (and generally should) free indices[]
 43:   */
 44:   PetscFree(indices);

 46:   /*
 47:      Print the index set to stdout
 48:   */
 49:   ISView(is,PETSC_VIEWER_STDOUT_SELF);

 51:   /*
 52:      Get the number of indices in the set 
 53:   */
 54:   ISGetLocalSize(is,&n);

 56:   /*
 57:      Get the indices in the index set
 58:   */
 59:   ISGetIndices(is,&indices);
 60:   /*
 61:      Now any code that needs access to the list of integers
 62:    has access to it here through indices[].
 63:    */
 64:   PetscPrintf(PETSC_COMM_SELF,"[%d] First index %dn",rank,indices[0]);

 66:   /*
 67:      Once we no longer need access to the indices they should 
 68:      returned to the system 
 69:   */
 70:   ISRestoreIndices(is,&indices);

 72:   /*
 73:      One should destroy any PETSc object once one is completely
 74:     done with it.
 75:   */
 76:   ISDestroy(is);
 77:   PetscFinalize();
 78:   return 0;
 79: }
 80: