subroutine d1f4kb ( ido, l1, cc, in1, ch, in2, wa1, wa2, wa3 )

!*****************************************************************************80
!
!! D1F4KB is an FFTPACK5 auxiliary routine.
!
!
!
!  Modified:
!
!    27 March 2009
!
!  Author:
!
!    Original real single precision by Paul Swarztrauber, Richard Valent.
!    Real double precision version by John Burkardt.
!
!  Reference:
!
!    Paul Swarztrauber,
!    Vectorizing the Fast Fourier Transforms,
!    in Parallel Computations,
!    edited by G. Rodrigue,
!    Academic Press, 1982.
!
!    Paul Swarztrauber,
!    Fast Fourier Transform Algorithms for Vector Computers,
!    Parallel Computing, pages 45-63, 1984.
!
!  Parameters:
!
  implicit none

  integer ( kind = 4 ) ido
  integer ( kind = 4 ) in1
  integer ( kind = 4 ) in2
  integer ( kind = 4 ) l1

  real ( kind = 8 ) cc(in1,ido,4,l1)
  real ( kind = 8 ) ch(in2,ido,l1,4)
  integer ( kind = 4 ) i
  integer ( kind = 4 ) ic
  integer ( kind = 4 ) idp2
  integer ( kind = 4 ) k
  real ( kind = 8 ) sqrt2
  real ( kind = 8 ) wa1(ido)
  real ( kind = 8 ) wa2(ido)
  real ( kind = 8 ) wa3(ido)

  sqrt2 = sqrt ( 2.0D+00 )

  do k = 1, l1
    ch(1,1,k,3) = ( cc(1,1,1,k)   + cc(1,ido,4,k) ) &
                - ( cc(1,ido,2,k) + cc(1,ido,2,k) )
    ch(1,1,k,1) = ( cc(1,1,1,k)   + cc(1,ido,4,k) ) &
                + ( cc(1,ido,2,k) + cc(1,ido,2,k) )
    ch(1,1,k,4) = ( cc(1,1,1,k)   - cc(1,ido,4,k) ) &
                + ( cc(1,1,3,k)   + cc(1,1,3,k) )
    ch(1,1,k,2) = ( cc(1,1,1,k)   - cc(1,ido,4,k) ) &
                - ( cc(1,1,3,k)   + cc(1,1,3,k) )
  end do

  if ( ido < 2 ) then
    return
  end if

  if ( 2 < ido ) then

    idp2 = ido + 2

    do k = 1, l1
      do i = 3, ido, 2
        ic = idp2 - i
        ch(1,i-1,k,1) = (cc(1,i-1,1,k)+cc(1,ic-1,4,k)) &
          +(cc(1,i-1,3,k)+cc(1,ic-1,2,k))
        ch(1,i,k,1) = (cc(1,i,1,k)-cc(1,ic,4,k)) &
          +(cc(1,i,3,k)-cc(1,ic,2,k))
        ch(1,i-1,k,2) = wa1(i-2)*((cc(1,i-1,1,k)-cc(1,ic-1,4,k)) &
          -(cc(1,i,3,k)+cc(1,ic,2,k)))-wa1(i-1) &
          *((cc(1,i,1,k)+cc(1,ic,4,k))+(cc(1,i-1,3,k)-cc(1,ic-1,2,k)))
        ch(1,i,k,2) = wa1(i-2)*((cc(1,i,1,k)+cc(1,ic,4,k)) &
          +(cc(1,i-1,3,k)-cc(1,ic-1,2,k)))+wa1(i-1) &
          *((cc(1,i-1,1,k)-cc(1,ic-1,4,k))-(cc(1,i,3,k)+cc(1,ic,2,k)))
        ch(1,i-1,k,3) = wa2(i-2)*((cc(1,i-1,1,k)+cc(1,ic-1,4,k)) &
          -(cc(1,i-1,3,k)+cc(1,ic-1,2,k)))-wa2(i-1) &
          *((cc(1,i,1,k)-cc(1,ic,4,k))-(cc(1,i,3,k)-cc(1,ic,2,k)))
        ch(1,i,k,3) = wa2(i-2)*((cc(1,i,1,k)-cc(1,ic,4,k)) &
          -(cc(1,i,3,k)-cc(1,ic,2,k)))+wa2(i-1) &
          *((cc(1,i-1,1,k)+cc(1,ic-1,4,k))-(cc(1,i-1,3,k) &
          +cc(1,ic-1,2,k)))
        ch(1,i-1,k,4) = wa3(i-2)*((cc(1,i-1,1,k)-cc(1,ic-1,4,k)) &
          +(cc(1,i,3,k)+cc(1,ic,2,k)))-wa3(i-1) &
          *((cc(1,i,1,k)+cc(1,ic,4,k))-(cc(1,i-1,3,k)-cc(1,ic-1,2,k)))
        ch(1,i,k,4) = wa3(i-2)*((cc(1,i,1,k)+cc(1,ic,4,k)) &
          -(cc(1,i-1,3,k)-cc(1,ic-1,2,k)))+wa3(i-1) &
          *((cc(1,i-1,1,k)-cc(1,ic-1,4,k))+(cc(1,i,3,k)+cc(1,ic,2,k)))
      end do
    end do

    if ( mod ( ido, 2 ) == 1 ) then
      return
    end if

  end if

  do k = 1, l1
    ch(1,ido,k,1) = ( cc(1,ido,1,k) + cc(1,ido,3,k) ) &
                  + ( cc(1,ido,1,k) + cc(1,ido,3,k))
    ch(1,ido,k,2) = sqrt2 * ( ( cc(1,ido,1,k) - cc(1,ido,3,k) ) &
                            - ( cc(1,1,2,k)   + cc(1,1,4,k) ) )
    ch(1,ido,k,3) = ( cc(1,1,4,k) - cc(1,1,2,k) ) &
                  + ( cc(1,1,4,k) - cc(1,1,2,k) )
    ch(1,ido,k,4) = -sqrt2 * ( ( cc(1,ido,1,k) - cc(1,ido,3,k) ) &
                             + ( cc(1,1,2,k) + cc(1,1,4,k) ) )
  end do

  return
end