subroutine sint1(n,War,Was,Xh,x,Ifac)
use fftpack_kind
implicit none
integer :: i , Ifac , k , kc , modn , n , np1 , ns2
real(rk) :: t1 , t2 , War , Was , x , Xh , xhold
dimension War(*) , Was(*) , x(*) , Xh(*) , Ifac(*)
real(rk),parameter :: sqrt3 = sqrt(3.0_rk)
do i = 1 , n
Xh(i) = War(i)
War(i) = x(i)
enddo
if ( n<2 ) then
Xh(1) = Xh(1) + Xh(1)
elseif ( n==2 ) then
xhold = sqrt3*(Xh(1)+Xh(2))
Xh(2) = sqrt3*(Xh(1)-Xh(2))
Xh(1) = xhold
else
np1 = n + 1
ns2 = n/2
x(1) = 0.0_rk
do k = 1 , ns2
kc = np1 - k
t1 = Xh(k) - Xh(kc)
t2 = Was(k)*(Xh(k)+Xh(kc))
x(k+1) = t1 + t2
x(kc+1) = t2 - t1
enddo
modn = mod(n,2)
if ( modn/=0 ) x(ns2+2) = 4.0_rk*Xh(ns2+1)
call rfftf1(np1,x,Xh,War,Ifac)
Xh(1) = 0.5_rk*x(1)
do i = 3 , n , 2
Xh(i-1) = -x(i)
Xh(i) = Xh(i-2) + x(i-1)
enddo
if ( modn==0 ) Xh(n) = -x(n+1)
endif
do i = 1 , n
x(i) = War(i)
War(i) = Xh(i)
enddo
end subroutine sint1
