1: !
  2: !
  3: !  Description:  Illustrates the use of VecSetValues() to set
  4: !  multiple values at once; demonstrates VecGetArrayF90().
  5: !
  6: ! -----------------------------------------------------------------------

  8:       program main
  9: #include <petsc/finclude/petscvec.h>
 10:       use petscvec
 11:       implicit none

 13: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 14: !                 Beginning of program
 15: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 17:        PetscInt, parameter :: n=6
 18:        PetscScalar, dimension(n) ::  xwork
 19:        PetscScalar, pointer, dimension(:) ::  xx_v,yy_v
 20:        PetscInt, dimension(n) :: loc
 21:        PetscInt i
 22:        PetscErrorCode ierr
 23:        Vec     x,y

 25:        call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 26:        if (ierr /= 0) then
 27:          print*,'PetscInitialize failed'
 28:          stop
 29:        endif

 31: !  Create initial vector and duplicate it

 33:        call VecCreateSeq(PETSC_COMM_SELF,n,x,ierr);CHKERRA(ierr)
 34:        call VecDuplicate(x,y,ierr);CHKERRA(ierr)

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

 40:        do 10 i=1,n
 41:           loc(i) = i-1
 42:           xwork(i) = 10.0*real(i)
 43:   10   continue

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

 50:        call VecSetValues(x,n,loc,xwork,INSERT_VALUES,ierr);CHKERRA(ierr)

 52: !  Assemble vector

 54:        call VecAssemblyBegin(x,ierr);CHKERRA(ierr)
 55:        call VecAssemblyEnd(x,ierr);CHKERRA(ierr)

 57: !  View vector
 58:        call PetscObjectSetName(x, 'initial vector:',ierr);CHKERRA(ierr)
 59:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr);CHKERRA(ierr)
 60:        call VecCopy(x,y,ierr);CHKERRA(ierr)

 62: !  Get a pointer to vector data.
 63: !    - For default PETSc vectors, VecGetArrayF90() returns a pointer to
 64: !      the data array.  Otherwise, the routine is implementation dependent.
 65: !    - You MUST call VecRestoreArray() when you no longer need access to
 66: !      the array.

 68:        call VecGetArrayF90(x,xx_v,ierr);CHKERRA(ierr)
 69:        call VecGetArrayF90(y,yy_v,ierr);CHKERRA(ierr)

 71: !  Modify vector data

 73:        do 30 i=1,n
 74:           xx_v(i) = 100.0*real(i)
 75:           yy_v(i) = 1000.0*real(i)
 76:   30   continue

 78: !  Restore vectors

 80:        call VecRestoreArrayF90(x,xx_v,ierr);CHKERRA(ierr)
 81:        call VecRestoreArrayF90(y,yy_v,ierr);CHKERRA(ierr)

 83: !  View vectors
 84:        call PetscObjectSetName(x, 'new vector 1:',ierr);CHKERRA(ierr)
 85:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr);CHKERRA(ierr)

 87:        call PetscObjectSetName(y, 'new vector 2:',ierr);CHKERRA(ierr)
 88:        call VecView(y,PETSC_VIEWER_STDOUT_SELF,ierr);CHKERRA(ierr)

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

 93:        call VecDestroy(x,ierr);CHKERRA(ierr)
 94:        call VecDestroy(y,ierr);CHKERRA(ierr)
 95:        call PetscFinalize(ierr)
 96:        end

 98: !
 99: !/*TEST
100: !
101: !     test:
102: !
103: !TEST*/