1: !
  2: !
  3: !  Description:  Illustrates the use of VecSetValues() to set
  4: !  multiple values at once; demonstrates VecGetArrayF90().
  5: !
  6: !/*T
  7: !   Concepts: vectors^assembling vectors;
  8: !   Concepts: vectors^arrays;
  9: !   Concepts: Fortran90^assembling vectors;
 10: !   Processors: 1
 11: !T*/
 12: ! -----------------------------------------------------------------------

 14:       program main
 15:       implicit none

 17: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 18: !                    Include files
 19: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 20: !
 21: !  The following include statements are required for Fortran programs
 22: !  that use PETSc vectors:
 23: !     petscsys.h       - base PETSc routines
 24: !     petscvec.h    - vectors
 25: !     petscvec.h90  - to allow access to Fortran90 features of vectors

 27: #include <petsc/finclude/petscsys.h>
 28: #include <petsc/finclude/petscvec.h>
 29: #include <petsc/finclude/petscvec.h90>

 31: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 32: !                 Beginning of program
 33: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 35:        PetscScalar  xwork(6)
 36:        PetscScalar, pointer ::  xx_v(:),yy_v(:)
 37:        PetscInt i,n,loc(6)
 38:        PetscErrorCode ierr
 39:        Vec     x,y


 42:        call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 43:        n = 6

 45: !  Create initial vector and duplicate it

 47:        call VecCreateSeq(PETSC_COMM_SELF,n,x,ierr)
 48:        call VecDuplicate(x,y,ierr)

 50: !  Fill work arrays with vector entries and locations.  Note that
 51: !  the vector indices are 0-based in PETSc (for both Fortran and
 52: !  C vectors)

 54:        do 10 i=1,n
 55:           loc(i) = i-1
 56:           xwork(i) = 10.0*real(i)
 57:   10   continue

 59: !  Set vector values.  Note that we set multiple entries at once.
 60: !  Of course, usually one would create a work array that is the
 61: !  natural size for a particular problem (not one that is as long
 62: !  as the full vector).

 64:        call VecSetValues(x,n,loc,xwork,INSERT_VALUES,ierr)

 66: !  Assemble vector

 68:        call VecAssemblyBegin(x,ierr)
 69:        call VecAssemblyEnd(x,ierr)

 71: !  View vector
 72:        call PetscObjectSetName(x, 'initial vector:',ierr)
 73:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr)
 74:        call VecCopy(x,y,ierr)

 76: !  Get a pointer to vector data.
 77: !    - For default PETSc vectors, VecGetArrayF90() returns a pointer to
 78: !      the data array.  Otherwise, the routine is implementation dependent.
 79: !    - You MUST call VecRestoreArray() when you no longer need access to
 80: !      the array.

 82:        call VecGetArrayF90(x,xx_v,ierr)
 83:        call VecGetArrayF90(y,yy_v,ierr)

 85: !  Modify vector data

 87:        do 30 i=1,n
 88:           xx_v(i) = 100.0*real(i)
 89:           yy_v(i) = 1000.0*real(i)
 90:   30   continue

 92: !  Restore vectors

 94:        call VecRestoreArrayF90(x,xx_v,ierr)
 95:        call VecRestoreArrayF90(y,yy_v,ierr)

 97: !  View vectors
 98:        call PetscObjectSetName(x, 'new vector 1:',ierr)
 99:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr)

101:        call PetscObjectSetName(y, 'new vector 2:',ierr)
102:        call VecView(y,PETSC_VIEWER_STDOUT_SELF,ierr)

104: !  Free work space.  All PETSc objects should be destroyed when they
105: !  are no longer needed.

107:        call VecDestroy(x,ierr)
108:        call VecDestroy(y,ierr)
109:        call PetscFinalize(ierr)
110:        end