Actual source code: ex2.c


  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>

 21: int main(int argc,char **argv)
 22: {
 23:   PetscInt       i,n,first,step;
 24:   IS             set;
 25:   const PetscInt *indices;

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

 29:   n     = 10;
 30:   first = 3;
 31:   step  = 2;

 33:   /*
 34:     Create stride index set, starting at 3 with a stride of 2
 35:     Note each processor is generating its own index set
 36:     (in this case they are all identical)
 37:   */
 38:   ISCreateStride(PETSC_COMM_SELF,n,first,step,&set);
 39:   ISView(set,PETSC_VIEWER_STDOUT_SELF);

 41:   /*
 42:     Extract indices from set.
 43:   */
 44:   ISGetIndices(set,&indices);
 45:   PetscPrintf(PETSC_COMM_WORLD,"Printing indices directly\n");
 46:   for (i=0; i<n; i++) {
 47:     PetscPrintf(PETSC_COMM_WORLD,"%" PetscInt_FMT "\n",indices[i]);
 48:   }

 50:   ISRestoreIndices(set,&indices);

 52:   /*
 53:       Determine information on stride
 54:   */
 55:   ISStrideGetInfo(set,&first,&step);
 57:   ISDestroy(&set);
 58:   PetscFinalize();
 59:   return 0;
 60: }

 62: /*TEST

 64:    test:

 66: TEST*/