subroutine radb2(ido, l1, cc, ch, wa1)
use fftpack_kind, only: dp => rk
implicit none
integer, intent(in) :: ido, l1
real(dp), intent(in) :: cc(ido, 2, l1), wa1(*)
real(dp), intent(out) :: ch(ido, l1, 2)
real(dp) :: ti2, tr2
integer :: i, ic, idp2, k
do concurrent(k=1:l1)
ch(1, k, 1) = cc(1, 1, k) + cc(ido, 2, k)
ch(1, k, 2) = cc(1, 1, k) - cc(ido, 2, k)
end do
if (ido < 2) return
if (ido /= 2) then
idp2 = ido + 2
do concurrent(k=1:l1, i=3:ido:2)
ic = idp2 - i
ch(i - 1, k, 1) = cc(i - 1, 1, k) + cc(ic - 1, 2, k)
tr2 = cc(i - 1, 1, k) - cc(ic - 1, 2, k)
ch(i, k, 1) = cc(i, 1, k) - cc(ic, 2, k)
ti2 = cc(i, 1, k) + cc(ic, 2, k)
ch(i - 1, k, 2) = wa1(i - 2)*tr2 - wa1(i - 1)*ti2
ch(i, k, 2) = wa1(i - 2)*ti2 + wa1(i - 1)*tr2
end do
if (mod(ido, 2) == 1) return
end if
do concurrent(k=1:l1)
ch(ido, k, 1) = cc(ido, 1, k) + cc(ido, 1, k)
ch(ido, k, 2) = -(cc(1, 2, k) + cc(1, 2, k))
end do
end subroutine radb2
