2: static char help[] = "Demonstrates VecStrideNorm().\n\n";

  4: /*T
  5:    Concepts: vectors^norms of sub-vectors;
  6:    Processors: n
  7: T*/

  9: /*
 10:   Include "petscvec.h" so that we can use vectors.  Note that this file
 11:   automatically includes:
 12:      petscsys.h       - base PETSc routines   petscis.h     - index sets
 13:      petscviewer.h - viewers
 14: */

 16: #include <petscvec.h>

 20: int main(int argc,char **argv)
 21: {
 22:   Vec            x;               /* vectors */
 23:   PetscReal      norm;
 24:   PetscInt       n = 20;
 26:   PetscScalar    one = 1.0;

 28:   PetscInitialize(&argc,&argv,(char*)0,help);
 29:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);

 31:   /*
 32:      Create a vector, specifying only its global dimension.
 33:      When using VecCreate(), VecSetSizes() and VecSetFromOptions(),
 34:      the vector format (currently parallel,
 35:      shared, or sequential) is determined at runtime.  Also, the parallel
 36:      partitioning of the vector is determined by PETSc at runtime.

 38:      Routines for creating particular vector types directly are:
 39:         VecCreateSeq() - uniprocessor vector
 40:         VecCreateMPI() - distributed vector, where the user can
 41:                          determine the parallel partitioning
 42:         VecCreateShared() - parallel vector that uses shared memory
 43:                             (available only on the SGI); otherwise,
 44:                             is the same as VecCreateMPI()

 46:      With VecCreate(), VecSetSizes() and VecSetFromOptions() the option
 47:      -vec_type mpi or -vec_type shared causes the
 48:      particular type of vector to be formed.

 50:   */
 51:   VecCreate(PETSC_COMM_WORLD,&x);
 52:   VecSetSizes(x,PETSC_DECIDE,n);
 53:   VecSetBlockSize(x,2);
 54:   VecSetFromOptions(x);

 56:   /*
 57:      Set the vectors to entries to a constant value.
 58:   */
 59:   VecSet(x,one);

 61:   VecNorm(x,NORM_2,&norm);
 62:   PetscPrintf(PETSC_COMM_WORLD,"Norm of entire vector %g\n",(double)norm);

 64:   VecStrideNorm(x,0,NORM_2,&norm);
 65:   PetscPrintf(PETSC_COMM_WORLD,"Norm of sub-vector %g\n",(double)norm);

 67:   VecStrideNorm(x,1,NORM_2,&norm);
 68:   PetscPrintf(PETSC_COMM_WORLD,"Norm of sub-vector %g\n",(double)norm);

 70:   VecStrideNorm(x,1,NORM_1,&norm);
 71:   PetscPrintf(PETSC_COMM_WORLD,"Norm of sub-vector %g\n",(double)norm);

 73:   VecStrideNorm(x,1,NORM_INFINITY,&norm);
 74:   PetscPrintf(PETSC_COMM_WORLD,"Norm of sub-vector %g\n",(double)norm);

 76:   /*
 77:      Free work space.  All PETSc objects should be destroyed when they
 78:      are no longer needed.
 79:   */
 80:   VecDestroy(&x);
 81:   PetscFinalize();
 82:   return 0;
 83: }