Actual source code: ex2.c
petsc-3.4.2 2013-07-02

      2: static char help[] = "Demonstrates creating a stride index set.\n\n";

      4: /*T
      5:     Concepts: index sets^creating a stride index set;
      6:     Concepts: stride^creating a stride index set;
      7:     Concepts: IS^creating a stride index set;

      9:     Description: Creates an index set based on a stride. Views that index set
     10:     and then destroys it.
     11: T*/

     13: /*
     14:   Include petscis.h so we can use PETSc IS objects. Note that this automatically
     15:   includes petscsys.h.
     16: */

     18: #include <petscis.h>
     19: #include <petscviewer.h>

     23: int main(int argc,char **argv)
     24: {
     26:   PetscInt       i,n,first,step;
     27:   IS             set;
     28:   const PetscInt *indices;

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

     32:   n     = 10;
     33:   first = 3;
     34:   step  = 2;

     36:   /*
     37:     Create stride index set, starting at 3 with a stride of 2
     38:     Note each processor is generating its own index set
     39:     (in this case they are all identical)
     40:   */
     41:   ISCreateStride(PETSC_COMM_SELF,n,first,step,&set);
     42:   ISView(set,PETSC_VIEWER_STDOUT_SELF);

     44:   /*
     45:     Extract indices from set.
     46:   */
     47:   ISGetIndices(set,&indices);
     48:   PetscPrintf(PETSC_COMM_WORLD,"Printing indices directly\n");
     49:   for (i=0; i<n; i++) {
     50:     PetscPrintf(PETSC_COMM_WORLD,"%D\n",indices[i]);
     51:   }

     53:   ISRestoreIndices(set,&indices);

     55:   /*
     56:       Determine information on stride
     57:   */
     58:   ISStrideGetInfo(set,&first,&step);
     59:   if (first != 3 || step != 2) SETERRQ(PETSC_COMM_SELF,1,"Stride info not correct!\n");
     60:   ISDestroy(&set);
     61:   PetscFinalize();
     62:   return 0;
     63: }