!===============================================
! dotprod.f90

! calculate dot product and write result to
! a file
!===============================================
program dotprod

  !-------------------------------------------
  ! module containing precision parameter
  !-------------------------------------------
  use prec_mod,  only: rk

  !-------------------------------------------
  ! module containing derived type
  !-------------------------------------------
  use rvec3_mod, only: rvec3

  implicit none
  integer :: i
  real(rk) :: c1, c2
  type(rvec3) :: a(2), b(2)

  !-------------------------------------------
  ! set nvals for each vector
  !-------------------------------------------
  a(1)%nvals = 2
  a(2)%nvals = 3
  b(1)%nvals = 20
  b(2)%nvals = 30

  !----------------------------
  ! input vectors
  !----------------------------
  a(1)%x = (/ 1,2,3 /)
  a(2)%x = (/ 1,2,3 /)
  b(1)%x = (/ 4,5,6 /)
  b(2)%x = (/ 4,5,6 /)

  !----------------------------
  ! calculate dot product
  !----------------------------
  call dp(a(1)%x, b(1)%x, c1)
  call dp(a(2)%x, b(2)%x, c2)

  print*,a
  print*,b
  !----------------------------
  ! check magnitude
  !----------------------------
  if(abs(c2) < 1.0e-6) then
     print*,'---------------------------------------------------'
     print*,'Warning: magnitude of dot product is less than 1e-6'
     print*,'---------------------------------------------------'
  endif

  !----------------------------
  ! write result to file
  !----------------------------
  open(21, file='dot.d')
  write(21, '(a, e9.3)') 'dot product = ', c2
  write(21, '(a, es9.3)') 'dot product = ', c2
  close(21)
  print*,' '
  print*,'Output written to file dot.d'

end program dotprod