subroutine nonlin_map_calc(lat,ix_start, ix_end, emitx,emity,emitz, ref_orbit, det, ft_matrix)

  use bmad
  use mode3_mod
use da_interface, dummy => nonlin_map_calc

implicit none
type (lat_struct) lat
type(coord_struct), allocatable:: co(:), orbit(:), ref_orbit(:)
type(coord_struct) x_co

real(rp), allocatable:: ft_matrix(:,:)
real(rp) emitx,emity,emitz, det, tune(3)
integer i, i_dim/6/, n
integer ix_start, ix_end

logical err_flag, full_turn
logical first/.true./, err/.false./

call reallocate_coord(co,7)
if(first )then
   call set_on_off(rfcavity$,lat,on$,ref_orbit)
   call twiss3_at_start(lat,err)
       if(err)then
           print *,' mode3 calc error in init_phase_space'
           stop
       endif
       call twiss3_propagate_all(lat)
       call set_on_off(rfcavity$,lat,off$,ref_orbit)
       first = .false.
endif

call init_phase_space(lat%ele(ix_start), emitx,emity,emitz, co, i_dim)
call compute_ft_matrix(lat,ref_orbit,emitx,emity,emitz, ix_start, ix_end, co,  i_dim,full_turn, ft_matrix, x_co)
!call measure_ft(ft_matrix,det,tune)

return
end subroutine nonlin_map_calc