subroutine passb2(Ido,l1,Cc,Ch,Wa1)
use fftpack_kind
implicit none
real(rk) :: Cc , Ch , ti2 , tr2 , Wa1
integer :: i , Ido , k , l1
dimension Cc(Ido,2,l1) , Ch(Ido,l1,2) , Wa1(*)
if ( Ido>2 ) then
do k = 1 , l1
do i = 2 , Ido , 2
Ch(i-1,k,1) = Cc(i-1,1,k) + Cc(i-1,2,k)
tr2 = Cc(i-1,1,k) - Cc(i-1,2,k)
Ch(i,k,1) = Cc(i,1,k) + Cc(i,2,k)
ti2 = Cc(i,1,k) - Cc(i,2,k)
Ch(i,k,2) = Wa1(i-1)*ti2 + Wa1(i)*tr2
Ch(i-1,k,2) = Wa1(i-1)*tr2 - Wa1(i)*ti2
enddo
enddo
else
do k = 1 , l1
Ch(1,k,1) = Cc(1,1,k) + Cc(1,2,k)
Ch(1,k,2) = Cc(1,1,k) - Cc(1,2,k)
Ch(2,k,1) = Cc(2,1,k) + Cc(2,2,k)
Ch(2,k,2) = Cc(2,1,k) - Cc(2,2,k)
enddo
end if
end subroutine passb2
