!------------------------------
! dot product of two vectors
! of length 3
!------------------------------
subroutine dp(x,y,d)

  !---------------------------
  ! set kind
  !---------------------------
  use prec_mod, only: rk

  implicit none
  real(rk) :: d
  real(rk), dimension(3) :: x, y

  d = sum(x*y)

end subroutine dp