subroutine rfftb1(n,c,Ch,Wa,Ifac)
use fftpack_kind
implicit none
real(rk) :: c , Ch , Wa
integer :: i , idl1 , ido , Ifac , ip , iw , ix2 , ix3 , ix4 , k1 , &
l1 , l2 , n , na , nf
dimension Ch(*) , c(*) , Wa(*) , Ifac(*)
nf = Ifac(2)
na = 0
l1 = 1
iw = 1
do k1 = 1 , nf
ip = Ifac(k1+2)
l2 = ip*l1
ido = n/l2
idl1 = ido*l1
if ( ip==4 ) then
ix2 = iw + ido
ix3 = ix2 + ido
if ( na/=0 ) then
call radb4(ido,l1,Ch,c,Wa(iw),Wa(ix2),Wa(ix3))
else
call radb4(ido,l1,c,Ch,Wa(iw),Wa(ix2),Wa(ix3))
endif
na = 1 - na
elseif ( ip==2 ) then
if ( na/=0 ) then
call radb2(ido,l1,Ch,c,Wa(iw))
else
call radb2(ido,l1,c,Ch,Wa(iw))
endif
na = 1 - na
elseif ( ip==3 ) then
ix2 = iw + ido
if ( na/=0 ) then
call radb3(ido,l1,Ch,c,Wa(iw),Wa(ix2))
else
call radb3(ido,l1,c,Ch,Wa(iw),Wa(ix2))
endif
na = 1 - na
elseif ( ip/=5 ) then
if ( na/=0 ) then
call radbg(ido,ip,l1,idl1,Ch,Ch,Ch,c,c,Wa(iw))
else
call radbg(ido,ip,l1,idl1,c,c,c,Ch,Ch,Wa(iw))
endif
if ( ido==1 ) na = 1 - na
else
ix2 = iw + ido
ix3 = ix2 + ido
ix4 = ix3 + ido
if ( na/=0 ) then
call radb5(ido,l1,Ch,c,Wa(iw),Wa(ix2),Wa(ix3),Wa(ix4))
else
call radb5(ido,l1,c,Ch,Wa(iw),Wa(ix2),Wa(ix3),Wa(ix4))
endif
na = 1 - na
endif
l1 = l2
iw = iw + (ip-1)*ido
enddo
if ( na==0 ) return
do i = 1 , n
c(i) = Ch(i)
enddo
end subroutine rfftb1
