Actual source code: ex4f90.F

      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: !     petsc.h       - base PETSc routines
     24: !     petscvec.h    - vectors
     25: !     petscvec.h90  - to allow access to Fortran90 features of vectors

     27:  #include include/finclude/petsc.h
     28:  #include include/finclude/petscvec.h
     29: #include "include/finclude/petscvec.h90"

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

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

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

     44: !  Create initial vector and duplicate it

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

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

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

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

     63:        call VecSetValues(x,6,loc,xwork,INSERT_VALUES,ierr)

     65: !  Assemble vector

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

     70: !  View vector

     72:        write(6,20)
     73:   20   format('initial vector:')
     74:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr)
     75:        call VecCopy(x,y,ierr)

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

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

     86: !  Modify vector data

     88:        do 30 i=1,n
     89:           xx_v(i) = 100.0*i
     90:           yy_v(i) = 1000.0*i
     91:   30   continue

     93: !  Restore vectors

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

     98: !  View vectors

    100:        write(6,40)
    101:   40   format('new vector 1:')
    102:        call VecView(x,PETSC_VIEWER_STDOUT_SELF,ierr)

    104:        write(6,50)
    105:   50   format('new vector 2:')
    106:        call VecView(y,PETSC_VIEWER_STDOUT_SELF,ierr)

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

    111:        call VecDestroy(x,ierr)
    112:        call VecDestroy(y,ierr)
    113:        call PetscFinalize(ierr)
    114:        end
    115: