1: !
  2: !
  3:        subroutine ex7f(vec,comm)

  5: #include <petsc/finclude/petscsys.h>
  6: #include <petsc/finclude/petscvec.h>
  7: !
  8: !  This routine demonstates how a computational module may be written
  9: !  in Fortran and called from a C routine, passing down PETSc objects.
 10: !

 12:        PetscScalar      two
 13:        Vec              vec
 14:        MPI_Comm         comm
 15:        PetscErrorCode ierr
 16:        PetscMPIInt rank

 18:        two  = 2.0

 20: !
 21: !     The Objects vec,comm created in a C routine are now
 22: !     used in fortran routines.
 23: !
 24:        call VecSet(vec,two,ierr)
 25:        call MPI_Comm_rank(comm,rank,ierr)
 26:        call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr)

 28: !
 29: !  Now call C routine from Fortran, passing in the vector, communicator
 30: !
 31:        call ex7c(vec,comm,ierr)
 32: !
 33: !     IO from the fortran routines may cause all kinds of
 34: !
 35: ! 100   format ('[',i1,']',' Calling VecView from Fortran')
 36: !       write(6,100) rank
 37: !
 38: !  Now Call a Petsc Routine from Fortran
 39: !
 40:        call VecView(vec,PETSC_VIEWER_STDOUT_WORLD,ierr)
 41:        return
 42:        end