Using Coarrays to Parallelize Legacy Fortran Applications: Strategy and Case Study

Listing 7

Unoptimized collective sum routine.

subroutine vector_co_sum_serial(vector)

 real(rkind), intent(inout)  :: vector(:)[*]

 integer image

 sync all

 if (this_image() == 1) then

  do image = 2, num_images()

   vector(:)1 = vector(:)1 + vector(:)[image]

  end do

 end if

 sync all

 if (this_image()/ = 1) vector(:) = vector(:)1

 sync all

end subroutine