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:        PetscCallA(PetscInitialize(ierr))

 27: !  Create initial vector and duplicate it

 29:        PetscCallA(VecCreateSeq(PETSC_COMM_SELF,n,x,ierr))
 30:        PetscCallA(VecDuplicate(x,y,ierr))

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

 36:        do 10 i=1,n
 37:           loc(i) = i-1
 38:           xwork(i) = 10.0*real(i)
 39:   10   continue

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

 46:        PetscCallA(VecSetValues(x,n,loc,xwork,INSERT_VALUES,ierr))

 48: !  Assemble vector

 50:        PetscCallA(VecAssemblyBegin(x,ierr))
 51:        PetscCallA(VecAssemblyEnd(x,ierr))

 53: !  View vector
 54:        PetscCallA(PetscObjectSetName(x, 'initial vector:',ierr))
 55:        PetscCallA(VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr))
 56:        PetscCallA(VecCopy(x,y,ierr))

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

 64:        PetscCallA(VecGetArrayF90(x,xx_v,ierr))
 65:        PetscCallA(VecGetArrayF90(y,yy_v,ierr))

 67: !  Modify vector data

 69:        do 30 i=1,n
 70:           xx_v(i) = 100.0*real(i)
 71:           yy_v(i) = 1000.0*real(i)
 72:   30   continue

 74: !  Restore vectors

 76:        PetscCallA(VecRestoreArrayF90(x,xx_v,ierr))
 77:        PetscCallA(VecRestoreArrayF90(y,yy_v,ierr))

 79: !  View vectors
 80:        PetscCallA(PetscObjectSetName(x, 'new vector 1:',ierr))
 81:        PetscCallA(VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr))

 83:        PetscCallA(PetscObjectSetName(y, 'new vector 2:',ierr))
 84:        PetscCallA(VecView(y,PETSC_VIEWER_STDOUT_SELF,ierr))

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

 89:        PetscCallA(VecDestroy(x,ierr))
 90:        PetscCallA(VecDestroy(y,ierr))
 91:        PetscCallA(PetscFinalize(ierr))
 92:        end

 94: !
 95: !/*TEST
 96: !
 97: !     test:
 98: !
 99: !TEST*/