如何修复 Array 'f' cannot have a deferred shape 错误？

我正在尝试使用 GNU Fortran 编译器使用四阶 Runge-Kutta 方法求解具有复杂变量的 SDE。如何解决“Array 'f' cannot have a deferred shape”错误？

program main
      integer, parameter :: n = 3, nsteps = 100
      real, parameter :: a = 0.0, b =1.0
      real ::  x(0:n)

      real :: d, hbar,W,omega0,omega,gamma1, E, delta
      d=3.335641E-30
      hbar=1.0546e-34
      omega = 2.482/(6.24e18*hbar)
      W = 1.25e10
      omega0= 2.4743/(6.24e18*hbar)
      delta=0.0
      gamma1= 1E15
      E=(1/hbar)*W;
      x = (/1.0, 0.0, 0.0,0.0/)
      h = (b - a)/nsteps
      call rk4sys(n,h,x,nsteps)
end program main



subroutine xpsys(n,x,f)
      complex, dimension (0:n) ::  x, f
      integer n

      f(0)= (-(0., 1.))*d*x(1)*E - x(2)*E+gamma1*x(4) ! 00+
      f(1)= ((0., -1.)*(x(2)*(delta)+ d*E*(x(0)- x(3)))-gamma1*x(2)/2)!11
      f(2)= (0., 1.)*(x(2)*(delta)+ d*E*(x(0)- x(3)))-gamma1*x(2)/2!10
      f(3)= (0., 1.)*d*(x(1)*E- x(2)*E)-gamma1*x(3)!01

end subroutine xpsys

subroutine rk4sys(n,h,x,nsteps)
      complex ::  x(0:n), f(:,:)
      real, allocatable :: y(:)
      integer :: i, k, n
      real :: h
      print *,0,x
      allocate (y(0:n), f(0:n,4))
    out:  do k = 1,nsteps
            call xpsys(n,x,f(0,1))
    in1:    do i = 0,n
              y(i) = x(i) + 0.5*h*f(i,1)
            end do in1
            call xpsys(n,y,f(0,2))
    in2:    do i = 0,n
              y(i) = x(i) + 0.5*h*f(i,2)
            end do in2
            call xpsys(n,y,f(0,3))
    in3:    do i = 0,n
              y(i) = x(i) + h*f(i,3)
            end do in3
            call xpsys(n,y,f(0,4))
    in4:    do i = 0,n
              x(i) = x(i) + (h/6.0)* (f(i,1) + 2.0*(f(i,2) + f(i,3)) + f(i,4))
            end do in4
            print *, k, x
          end do out
end subroutine rk4sys