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: #include <petsc/finclude/petscvec.h>
 16:       use petscvec
 17:       implicit none

 19: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 20: !                 Beginning of program
 21: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 23:        PetscInt, parameter :: n=6
 24:        PetscScalar, dimension(n) ::  xwork
 25:        PetscScalar, pointer, dimension(:) ::  xx_v,yy_v
 26:        PetscInt, dimension(n) :: loc
 27:        PetscInt i
 28:        PetscErrorCode ierr
 29:        Vec     x,y


 32:        call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
 33:        if (ierr /= 0) then
 34:          print*,'PetscInitialize failed'
 35:          stop
 36:        endif

 38: !  Create initial vector and duplicate it

 40:        call VecCreateSeq(PETSC_COMM_SELF,n,x,ierr);CHKERRA(ierr)
 41:        call VecDuplicate(x,y,ierr);CHKERRA(ierr)

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

 47:        do 10 i=1,n
 48:           loc(i) = i-1
 49:           xwork(i) = 10.0*real(i)
 50:   10   continue

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

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

 59: !  Assemble vector

 61:        call VecAssemblyBegin(x,ierr);CHKERRA(ierr)
 62:        call VecAssemblyEnd(x,ierr);CHKERRA(ierr)

 64: !  View vector
 65:        call PetscObjectSetName(x, 'initial vector:',ierr);CHKERRA(ierr)
 66:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr);CHKERRA(ierr)
 67:        call VecCopy(x,y,ierr);CHKERRA(ierr)

 69: !  Get a pointer to vector data.
 70: !    - For default PETSc vectors, VecGetArrayF90() returns a pointer to
 71: !      the data array.  Otherwise, the routine is implementation dependent.
 72: !    - You MUST call VecRestoreArray() when you no longer need access to
 73: !      the array.

 75:        call VecGetArrayF90(x,xx_v,ierr);CHKERRA(ierr)
 76:        call VecGetArrayF90(y,yy_v,ierr);CHKERRA(ierr)

 78: !  Modify vector data

 80:        do 30 i=1,n
 81:           xx_v(i) = 100.0*real(i)
 82:           yy_v(i) = 1000.0*real(i)
 83:   30   continue

 85: !  Restore vectors

 87:        call VecRestoreArrayF90(x,xx_v,ierr);CHKERRA(ierr)
 88:        call VecRestoreArrayF90(y,yy_v,ierr);CHKERRA(ierr)

 90: !  View vectors
 91:        call PetscObjectSetName(x, 'new vector 1:',ierr);CHKERRA(ierr)
 92:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr);CHKERRA(ierr)

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

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

100:        call VecDestroy(x,ierr);CHKERRA(ierr)
101:        call VecDestroy(y,ierr);CHKERRA(ierr)
102:        call PetscFinalize(ierr)
103:        end

105: !
106: !/*TEST
107: !
108: !     test:
109: !
110: !TEST*/