program pt2
  implicit none
  BEGIN_DOC
  ! Second order perturbative correction to the wave function contained in the EZFIO directory.
  !
  ! This programs runs the stochastic PT2 correction on all "n_states" wave function stored in the EZFIO folder (see :option:`determinant n_states`).
  !
  ! The option for the PT2 correction are the "pt2_relative_error" which is the relative stochastic
  !
  ! error on the PT2 to reach before stopping the stochastic sampling. (see :option:`perturbation pt2_relative_error`)
  END_DOC
  if (.not. is_zmq_slave) then
    read_wf = .True.
    threshold_generators = 1.d0
    SOFT_TOUCH read_wf threshold_generators
    PROVIDE mo_two_e_integrals_in_map
    PROVIDE psi_energy
    call run
  else
    call run_slave_cipsi
  endif
end

subroutine run
  implicit none
  integer                        :: i,j,k
  logical, external              :: detEq

  double precision               :: pt2(N_states)
  integer                        :: degree
  integer                        :: n_det_before, to_select
  double precision               :: threshold_davidson_in

  double precision               :: E_CI_before(N_states), relative_error, error(N_states), variance(N_states), norm(N_states), rpt2(N_states)

  pt2(:) = 0.d0

  E_CI_before(:) = psi_energy(:) + nuclear_repulsion
  relative_error=PT2_relative_error

  call ZMQ_pt2(psi_energy_with_nucl_rep,pt2,relative_error,error, variance, &
     norm,0) ! Stochastic PT2
  do k=1,N_states
    rpt2(:) = pt2(:)/(1.d0 + norm(k))
  enddo

  call print_summary(psi_energy_with_nucl_rep(1:N_states),pt2,error,variance,norm,N_det,N_occ_pattern,N_states,psi_s2)

  call save_energy(E_CI_before,pt2)
end