tmc_tree_build.F

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!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright 2000-2026 CP2K developers group <https://cp2k.org>                                   !
!                                                                                                  !
!   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
!--------------------------------------------------------------------------------------------------!
 
! **************************************************************************************************
!> \brief tree nodes creation, deallocation, references etc.
!>        - we distinguish two kinds of tree nodes: global and sub tree nodes
!>          (because we also are able to do parallel tempering)
!>        - global tree nodes consists of pointers to sub tree nodes
!>        - sub tree nodes consists of position arrays, potential energy, etc.
!>        - furthermore the sub tree elements have references the all global
!>          tree elements referring to them
!>        - for tree element details see tree_types.F
!>
!>        - for creating we always start with the global tree element
!>          (if not already exist)
!>        - for each new global tree element (depending on the move type):
!>           - two sub tree elements are swapped (Parallel Tempering)
!>             (in global tree element creation)
!>           - the volume of a subtree element is changed
!>             (directly in sub tree element creation)
!>           - positions in one subtree element changes
!>             (in sub tree elem creation or NMC)
!>           - ...
!>        - sub tree elements will be deleted only if no reference to
!>          any global tree element exist anymore
!> \par History
!>      11.2012 created [Mandes Schoenherr]
!> \author Mandes
! **************************************************************************************************
 
MODULE tmc_tree_build
   USE cp_log_handling,                 ONLY: cp_to_string
   USE kinds,                           ONLY: dp
   USE tmc_calculations,                ONLY: calc_e_kin,&
                                              init_vel
   USE tmc_dot_tree,                    ONLY: create_dot,&
                                              create_dot_color,&
                                              create_global_tree_dot,&
                                              create_global_tree_dot_color
   USE tmc_file_io,                     ONLY: read_restart_file,&
                                              write_result_list_element
   USE tmc_move_handle,                 ONLY: select_random_move_type
   USE tmc_move_types,                  ONLY: &
        mv_type_md, mv_type_nmc_moves, mv_type_atom_swap, mv_type_atom_trans, &
        mv_type_gausian_adapt, mv_type_mol_rot, mv_type_mol_trans, mv_type_none, &
        mv_type_proton_reorder, mv_type_swap_conf, mv_type_volume_move
   USE tmc_moves,                       ONLY: change_pos,&
                                              elements_in_new_subbox
   USE tmc_stati,                       ONLY: tmc_status_failed,&
                                              tmc_status_wait_for_new_task,&
                                              task_type_mc,&
                                              task_type_gaussian_adaptation
   USE tmc_tree_references,             ONLY: add_to_references,&
                                              remove_gt_references,&
                                              remove_subtree_element_of_all_references,&
                                              search_and_remove_reference_in_list
   USE tmc_tree_search,                 ONLY: most_prob_end,&
                                              search_end_of_clean_g_tree,&
                                              search_end_of_clean_tree,&
                                              search_parent_element
   USE tmc_tree_types,                  ONLY: &
        add_to_list, elem_array_type, global_tree_type, status_accepted, status_accepted_result, &
        status_calc_approx_ener, status_calculate_md, status_calculate_nmc_steps, &
        status_calculate_energy, status_calculated, status_cancel_ener, status_cancel_nmc, &
        status_canceled_ener, status_canceled_nmc, status_created, status_deleted, &
        status_deleted_result, status_ok, status_rejected, status_rejected_result, tree_type
   USE tmc_types,                       ONLY: tmc_env_type,&
                                              tmc_param_type
#include "../base/base_uses.f90"
 
   IMPLICIT NONE
 
   PRIVATE
 
   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'tmc_tree_build'
 
   PUBLIC :: allocate_new_sub_tree_node, deallocate_sub_tree_node
   PUBLIC :: init_tree_mod, finalize_init
   PUBLIC :: create_new_gt_tree_node
   PUBLIC :: remove_unused_g_tree
   PUBLIC :: remove_all_trees
   PUBLIC :: finalize_trees
CONTAINS
 
   !********************************************************************************
   ! ALLOCATION - DEALLOCATION
   !********************************************************************************
! **************************************************************************************************
!> \brief allocates an elements of the global element structure
!> \param next_el ...
!> \param nr_temp ...
!> \author Mandes 11.2012
! **************************************************************************************************
   SUBROUTINE allocate_new_global_tree_node(next_el, nr_temp)
      TYPE(global_tree_type), POINTER                    :: next_el
      INTEGER                                            :: nr_temp
 
      CHARACTER(LEN=*), PARAMETER :: routineN = 'allocate_new_global_tree_node'
 
      INTEGER                                            :: handle, itmp
 
      cpassert(.NOT. ASSOCIATED(next_el))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      ! allocate everything
      ALLOCATE (next_el)
      ALLOCATE (next_el%conf(nr_temp))
      ALLOCATE (next_el%conf_n_acc(nr_temp))
      next_el%rnd_nr = -1.0_dp
 
      DO itmp = 1, nr_temp
         NULLIFY (next_el%conf(itmp)%elem)
         next_el%conf_n_acc(itmp) = .false.
      END DO
 
      next_el%swaped = .false.
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE allocate_new_global_tree_node
 
! **************************************************************************************************
!> \brief deallocates an elements of the global element structure
!> \param gt_elem ...
!> \author Mandes 11.2012
! **************************************************************************************************
   SUBROUTINE deallocate_global_tree_node(gt_elem)
      TYPE(global_tree_type), POINTER                    :: gt_elem
 
      CHARACTER(LEN=*), PARAMETER :: routineN = 'deallocate_global_tree_node'
 
      INTEGER                                            :: handle
 
      cpassert(ASSOCIATED(gt_elem))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      ! deallocate everything
      DEALLOCATE (gt_elem%conf_n_acc)
      DEALLOCATE (gt_elem%conf)
      DEALLOCATE (gt_elem)
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE deallocate_global_tree_node
 
! **************************************************************************************************
!> \brief allocates an elements of the subtree element structure
!> \param tmc_params structure for storing all (global) parameters
!> \param next_el ...
!> \param nr_dim ...
!> \author Mandes 11.2012
! **************************************************************************************************
   SUBROUTINE allocate_new_sub_tree_node(tmc_params, next_el, nr_dim)
      TYPE(tmc_param_type), POINTER                      :: tmc_params
      TYPE(tree_type), POINTER                           :: next_el
      INTEGER                                            :: nr_dim
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'allocate_new_sub_tree_node'
 
      INTEGER                                            :: handle
 
      cpassert(.NOT. ASSOCIATED(next_el))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      ALLOCATE (next_el)
      NULLIFY (next_el%subbox_center, next_el%pos, next_el%mol, next_el%vel, &
               next_el%frc, next_el%dipole, next_el%elem_stat, &
               next_el%gt_nodes_references)
 
      next_el%scf_energies(:) = huge(next_el%scf_energies)
      next_el%scf_energies_count = 0
      ALLOCATE (next_el%pos(nr_dim))
      ALLOCATE (next_el%mol(nr_dim/tmc_params%dim_per_elem))
      ALLOCATE (next_el%vel(nr_dim))
      IF (tmc_params%print_dipole) ALLOCATE (next_el%dipole(tmc_params%dim_per_elem))
      ALLOCATE (next_el%elem_stat(nr_dim))
      next_el%elem_stat = status_ok
      ALLOCATE (next_el%subbox_center(tmc_params%dim_per_elem))
      IF (tmc_params%print_forces .OR. tmc_params%task_type == task_type_gaussian_adaptation) THEN
         IF (tmc_params%task_type == task_type_gaussian_adaptation) THEN
            ALLOCATE (next_el%frc(nr_dim*nr_dim))
         ELSE
            ALLOCATE (next_el%frc(nr_dim))
         END IF
         next_el%frc = 0.0_dp
      END IF
      ALLOCATE (next_el%box_scale(3))
      next_el%pos(:) = -1.0_dp
      next_el%mol(:) = -1
      next_el%box_scale(:) = 1.0_dp
      next_el%scf_energies(:) = 0.0_dp
      next_el%e_pot_approx = 0.0_dp
      next_el%potential = 76543.0_dp
      next_el%vel = 0.0_dp ! standart MC don"t uses velocities, but it is used at least in acceptance check
      next_el%ekin = 0.0_dp
      next_el%ekin_before_md = 0.0_dp
      next_el%sub_tree_nr = 0
      next_el%nr = -1
      next_el%rng_seed(:, :, :) = -1.0_dp
      next_el%move_type = mv_type_none
 
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE allocate_new_sub_tree_node
 
! **************************************************************************************************
!> \brief deallocates an elements of the subtree element structure
!> \param tree_elem ...
!> \author Mandes 11.2012
! **************************************************************************************************
   SUBROUTINE deallocate_sub_tree_node(tree_elem)
      TYPE(tree_type), POINTER                           :: tree_elem
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'deallocate_sub_tree_node'
 
      INTEGER                                            :: handle
 
      cpassert(ASSOCIATED(tree_elem))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      ! reference handling
      ! should be not necessary, subtree element should be only deallocated,
      !   if no global tree element points to anymore
      CALL remove_subtree_element_of_all_references(ptr=tree_elem)
 
      IF (ASSOCIATED(tree_elem%box_scale)) DEALLOCATE (tree_elem%box_scale)
      IF (ASSOCIATED(tree_elem%frc)) DEALLOCATE (tree_elem%frc)
      IF (ASSOCIATED(tree_elem%subbox_center)) DEALLOCATE (tree_elem%subbox_center)
      IF (ASSOCIATED(tree_elem%elem_stat)) DEALLOCATE (tree_elem%elem_stat)
      IF (ASSOCIATED(tree_elem%dipole)) DEALLOCATE (tree_elem%dipole)
      IF (ASSOCIATED(tree_elem%vel)) DEALLOCATE (tree_elem%vel)
      IF (ASSOCIATED(tree_elem%mol)) DEALLOCATE (tree_elem%mol)
      IF (ASSOCIATED(tree_elem%pos)) DEALLOCATE (tree_elem%pos)
 
      DEALLOCATE (tree_elem)
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE deallocate_sub_tree_node
 
   !********************************************************************************
   ! INITIALIZATION - FINALIZE
   !********************************************************************************
 
! **************************************************************************************************
!> \brief routine initiate the global and subtrees with the first elements
!> \param start_elem ...
!> \param tmc_env structure for storing all (global) parameters
!> \param job_counts ...
!> \param worker_timings ...
!> \author Mandes 11.2012
! **************************************************************************************************
   SUBROUTINE init_tree_mod(start_elem, tmc_env, job_counts, worker_timings)
      TYPE(tree_type), POINTER                           :: start_elem
      TYPE(tmc_env_type), POINTER                        :: tmc_env
      INTEGER, DIMENSION(:)                              :: job_counts
      REAL(kind=dp), DIMENSION(4)                        :: worker_timings
 
      CHARACTER(LEN=*), PARAMETER                        :: routinen = 'init_tree_mod'
 
      INTEGER                                            :: handle, i
      TYPE(global_tree_type), POINTER                    :: global_tree
 
      NULLIFY (global_tree)
 
      cpassert(ASSOCIATED(start_elem))
      cpassert(ASSOCIATED(tmc_env))
      cpassert(ASSOCIATED(tmc_env%m_env))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      ! allocate everything
      CALL allocate_new_global_tree_node(next_el=tmc_env%m_env%gt_act, &
                                         nr_temp=tmc_env%params%nr_temp)
 
      ! use initial/default values
      CALL tmc_env%rng_stream%get( &
         bg=tmc_env%m_env%gt_act%rng_seed(:, :, 1), &
         cg=tmc_env%m_env%gt_act%rng_seed(:, :, 2), &
         ig=tmc_env%m_env%gt_act%rng_seed(:, :, 3))
 
      global_tree => tmc_env%m_env%gt_act
      tmc_env%m_env%gt_head => tmc_env%m_env%gt_act
 
      ! set global random seed
      CALL tmc_env%rng_stream%set(bg=global_tree%rng_seed(:, :, 1), &
                                  cg=global_tree%rng_seed(:, :, 2), &
                                  ig=global_tree%rng_seed(:, :, 3))
      global_tree%rnd_nr = tmc_env%rng_stream%next()
 
      !-- SUBTREES: set initial values
      DO i = 1, SIZE(global_tree%conf)
         CALL allocate_new_sub_tree_node(tmc_env%params, next_el=global_tree%conf(i)%elem, &
                                         nr_dim=SIZE(start_elem%pos))
         global_tree%conf(i)%elem%move_type = 0
         global_tree%conf(i)%elem%next_elem_nr => tmc_env%m_env%tree_node_count(i)
         global_tree%conf(i)%elem%parent => null()
         global_tree%conf(i)%elem%nr = global_tree%conf(i)%elem%next_elem_nr
         global_tree%conf(i)%elem%sub_tree_nr = i
         global_tree%conf(i)%elem%elem_stat = status_ok
         global_tree%conf(i)%elem%pos = start_elem%pos
         global_tree%conf(i)%elem%mol = start_elem%mol
         global_tree%conf(i)%elem%e_pot_approx = start_elem%e_pot_approx
         global_tree%conf(i)%elem%temp_created = i
         global_tree%conf(i)%elem%stat = status_calculate_energy
         !it is default already: global_tree%conf(i)%elem%box_scale(:)  = 1.0_dp
         IF (tmc_env%params%task_type == task_type_gaussian_adaptation) THEN
            global_tree%conf(i)%elem%vel(:) = start_elem%vel(:)
            global_tree%conf(i)%elem%frc(:) = start_elem%frc(:)
            global_tree%conf(i)%elem%potential = start_elem%potential
            global_tree%conf(i)%elem%ekin = start_elem%ekin
            global_tree%conf(i)%elem%ekin_before_md = start_elem%ekin_before_md
         END IF
 
         !-- different random seeds for every subtree
         CALL tmc_env%rng_stream%reset_to_next_substream()
         CALL tmc_env%rng_stream%get(bg=global_tree%conf(i)%elem%rng_seed(:, :, 1), &
                                     cg=global_tree%conf(i)%elem%rng_seed(:, :, 2), &
                                     ig=global_tree%conf(i)%elem%rng_seed(:, :, 3))
 
         !-- gaussian distributed velocities
         !-- calculating the kinetic energy of the initial configuration velocity
         IF (tmc_env%params%task_type == task_type_mc) THEN
            IF (tmc_env%params%move_types%mv_weight(mv_type_md) > 0.0_dp) THEN
               CALL init_vel(vel=global_tree%conf(i)%elem%vel, atoms=tmc_env%params%atoms, &
                             temerature=tmc_env%params%Temp(i), &
                             rng_stream=tmc_env%rng_stream, &
                             rnd_seed=global_tree%conf(i)%elem%rng_seed)
               global_tree%conf(i)%elem%ekin = calc_e_kin(vel=global_tree%conf(i)%elem%vel, &
                                                          atoms=tmc_env%params%atoms)
            END IF
         END IF
 
         !-- set tree pointer
         !-- set pointer of first global tree element
         tmc_env%m_env%st_heads(i)%elem => global_tree%conf(i)%elem
         tmc_env%m_env%st_clean_ends(i)%elem => global_tree%conf(i)%elem
         !-- set initial pointer of result lists
         tmc_env%m_env%result_list(i)%elem => global_tree%conf(i)%elem
      END DO
      tmc_env%m_env%tree_node_count(:) = 0 ! initializing the tree node numbering
 
      !-- initial global tree element
      tmc_env%m_env%gt_head => global_tree
      tmc_env%m_env%gt_clean_end => global_tree
      global_tree%nr = 0
      global_tree%swaped = .false.
      global_tree%mv_conf = 1
      global_tree%mv_next_conf = modulo(global_tree%mv_conf, SIZE(global_tree%conf)) + 1
      global_tree%conf_n_acc = .true.
 
      global_tree%stat = status_created
      global_tree%prob_acc = 1.0_dp
 
      ! simulated annealing start temperature
      global_tree%Temp = tmc_env%params%Temp(1)
      IF (tmc_env%params%nr_temp /= 1 .AND. tmc_env%m_env%temp_decrease /= 1.0_dp) THEN
         CALL cp_abort(__location__, &
                       "there is no parallel tempering implementation for simulated annealing implemented "// &
                       "(just one Temp per global tree element.")
      END IF
 
      !-- IF program is restarted, read restart file
      IF (tmc_env%m_env%restart_in_file_name /= "") THEN
         CALL read_restart_file(tmc_env=tmc_env, job_counts=job_counts, &
                                timings=worker_timings, &
                                file_name=tmc_env%m_env%restart_in_file_name)
 
         tmc_env%m_env%tree_node_count(0) = global_tree%nr
 
         DO i = 1, SIZE(tmc_env%m_env%result_list(:))
            tmc_env%m_env%tree_node_count(i) = tmc_env%m_env%result_list(i)%elem%nr
            global_tree%conf(i)%elem%stat = status_accepted
         END DO
         global_tree%prob_acc = 1.0_dp ! accepted (re)start configuration
         WRITE (tmc_env%m_env%io_unit, *) "TMC| restarting at Markov Chain element(s): ", &
            tmc_env%m_env%result_count
         !TODO enable calculation of the approx energy for case of fitting potential
         !     and changing the potential in between
         !     BUT check, there is no double counting (of the last/restarted elem) in the trajectory
         !IF(tmc_env%params%NMC_inp_file/="") &
         !  global_tree%conf(1)%elem%stat  = status_calc_approx_ener
         global_tree%stat = status_accepted_result
      ELSE IF (tmc_env%params%NMC_inp_file /= "") THEN
         global_tree%conf(1)%elem%stat = status_calc_approx_ener
      ELSE
         global_tree%conf(1)%elem%stat = status_created
      END IF
 
      !-- set reference of global tree node
      CALL add_to_references(gt_elem=global_tree)
 
      !-- draw the first global tree node
      IF (tmc_env%params%DRAW_TREE) THEN
         CALL create_global_tree_dot(new_element=global_tree, &
                                     tmc_params=tmc_env%params)
         CALL create_global_tree_dot_color(gt_tree_element=global_tree, &
                                           tmc_params=tmc_env%params)
      END IF
 
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE init_tree_mod
 
! **************************************************************************************************
!> \brief distributes the initial energy to all subtree (if no restart) and
!>        call analysis for this element (write trajectory...)
!> \param gt_tree_ptr global tree head (initial configuration)
!> \param tmc_env master environment for restart
!>        (if restart the subtree heads are not equal), result counts and lists
!> \author Mandes 12.2012
! **************************************************************************************************
   SUBROUTINE finalize_init(gt_tree_ptr, tmc_env)
      TYPE(global_tree_type), POINTER                    :: gt_tree_ptr
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER                        :: routinen = 'finalize_init'
 
      INTEGER                                            :: handle, i
 
      cpassert(ASSOCIATED(gt_tree_ptr))
      cpassert(.NOT. ASSOCIATED(gt_tree_ptr%parent))
      cpassert(ASSOCIATED(tmc_env))
      cpassert(ASSOCIATED(tmc_env%m_env))
      cpassert(ASSOCIATED(tmc_env%params))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      gt_tree_ptr%stat = status_accepted_result
      !-- distribute energy of first element to all subtrees
      DO i = 1, SIZE(gt_tree_ptr%conf)
         gt_tree_ptr%conf(i)%elem%stat = status_accepted_result
         IF (ASSOCIATED(gt_tree_ptr%conf(1)%elem%dipole)) THEN
            gt_tree_ptr%conf(i)%elem%dipole = gt_tree_ptr%conf(1)%elem%dipole
         END IF
         IF (tmc_env%m_env%restart_in_file_name == "") THEN
            gt_tree_ptr%conf(i)%elem%potential = gt_tree_ptr%conf(1)%elem%potential
         END IF
      END DO
 
      IF (tmc_env%m_env%restart_in_file_name == "") THEN
         tmc_env%m_env%result_count(:) = tmc_env%m_env%result_count(:) + 1
         tmc_env%m_env%result_list(:) = gt_tree_ptr%conf(:)
         !-- write initial elements in result files
         DO i = 1, SIZE(tmc_env%m_env%result_list)
            CALL write_result_list_element(result_list=tmc_env%m_env%result_list, &
                                           result_count=tmc_env%m_env%result_count, &
                                           conf_updated=i, accepted=.true., &
                                           tmc_params=tmc_env%params)
            ! save for analysis
            IF (tmc_env%tmc_comp_set%para_env_m_ana%num_pe > 1) THEN
               CALL add_to_list(elem=tmc_env%m_env%result_list(i)%elem, &
                                list=tmc_env%m_env%analysis_list, &
                                nr=tmc_env%m_env%result_count(i), &
                                temp_ind=i)
            END IF
         END DO
         !CALL write_result_list_element(result_list=tmc_env%m_env%result_list, &
         !         result_count=tmc_env%m_env%result_count,&
         !         conf_updated=0, accepted=.TRUE., &
         !         tmc_params=tmc_env%params)
      END IF
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE finalize_init
 
   !============================================================================
   ! tree node creation
   !============================================================================
! **************************************************************************************************
!> \brief creates new global tree element and if needed new subtree element
!> \param tmc_env TMC environment with parameters and pointers to gt element
!> \param stat return status value
!> \param new_elem return gt element
!> \param reactivation_cc_count counting the reactivation of subtree elements
!> \author Mandes 12.2012
! **************************************************************************************************
   SUBROUTINE create_new_gt_tree_node(tmc_env, stat, new_elem, &
                                      reactivation_cc_count)
      TYPE(tmc_env_type), POINTER                        :: tmc_env
      INTEGER, INTENT(OUT)                               :: stat
      TYPE(global_tree_type), INTENT(OUT), POINTER       :: new_elem
      INTEGER                                            :: reactivation_cc_count
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'create_new_gt_tree_node'
      REAL(kind=dp), PARAMETER                           :: eps_exp_prob = 1.0e-10_dp
 
      INTEGER                                            :: handle, swap_conf
      LOGICAL                                            :: keep_on, n_acc
      REAL(kind=dp)                                      :: prob, rnd, rnd2
      TYPE(global_tree_type), POINTER                    :: tmp_elem
      TYPE(tree_type), POINTER                           :: tree_elem
 
      NULLIFY (tmp_elem, tree_elem, new_elem)
 
      cpassert(ASSOCIATED(tmc_env))
      cpassert(ASSOCIATED(tmc_env%params))
      cpassert(ASSOCIATED(tmc_env%m_env))
      cpassert(ASSOCIATED(tmc_env%m_env%gt_act))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      stat = tmc_status_failed
      !-- search most probable end in global tree for new element
      tmp_elem => tmc_env%m_env%gt_act
      n_acc = .true.
 
      !-- search most probable end to create new element
      CALL most_prob_end(global_tree_elem=tmp_elem, prob=prob, n_acc=n_acc)
 
      keep_on = .true.
      IF (ASSOCIATED(tmp_elem) .AND. (exp(prob) < eps_exp_prob)) THEN
         new_elem => null()
         stat = tmc_status_failed
         keep_on = .false.
         !-- if not found, do something else
         !-- (posible if just one end for further calculations
         !    and there a MD move is still calculated)
      ELSE IF (.NOT. ASSOCIATED(tmp_elem)) THEN
         new_elem => null()
         stat = tmc_status_failed
         keep_on = .false.
      END IF
 
      IF (keep_on) THEN
         ! if global tree element already exist use that one
         !   (skip creating new element)
         ! reactivation
         IF ((n_acc .AND. ASSOCIATED(tmp_elem%acc)) .OR. &
             ((.NOT. n_acc) .AND. ASSOCIATED(tmp_elem%nacc))) THEN
 
            !set pointer to the actual element
            IF (n_acc) THEN
               new_elem => tmp_elem%acc
            END IF
            IF (.NOT. n_acc) THEN
               new_elem => tmp_elem%nacc
            END IF
 
            ! check for existing subtree element
            cpassert(ASSOCIATED(new_elem%conf(new_elem%mv_conf)%elem))
            SELECT CASE (new_elem%conf(new_elem%mv_conf)%elem%stat)
            CASE (status_cancel_nmc, status_cancel_ener, status_canceled_nmc, &
                  status_canceled_ener)
               ! reactivating subtree element
               !  (but global tree element already exist)
               CALL add_to_references(gt_elem=new_elem)
               reactivation_cc_count = reactivation_cc_count + 1
            CASE DEFAULT
               CALL cp_abort(__location__, &
                             "global tree node creation using existing sub tree element, "// &
                             "but is not a canceled one, gt elem "// &
                             cp_to_string(new_elem%nr)//" st elem "// &
                             cp_to_string(new_elem%conf(new_elem%mv_conf)%elem%nr)// &
                             " with stat "// &
                             cp_to_string(new_elem%conf(new_elem%mv_conf)%elem%stat))
            END SELECT
            ! change the status of the reactivated subtree element
            ! move is only done by the master,
            !  when standard MC moves with single potential are done
            ! the Nested Monte Carlo routine needs to do the configuration
            !  to have old configuration to see if change is accepted
            SELECT CASE (new_elem%conf(new_elem%mv_conf)%elem%move_type)
            CASE (mv_type_md)
               new_elem%conf(new_elem%mv_conf)%elem%stat = status_calculate_md
            CASE (mv_type_nmc_moves)
               IF (new_elem%conf(new_elem%mv_conf)%elem%stat /= status_canceled_nmc) THEN
                  CALL cp_warn(__location__, &
                               "reactivating tree element with wrong status"// &
                               cp_to_string(new_elem%conf(new_elem%mv_conf)%elem%stat))
               END IF
               new_elem%conf(new_elem%mv_conf)%elem%stat = status_calculate_nmc_steps
 
               !IF(DEBUG>=1) WRITE(tmc_out_file_nr,*)"ATTENTION: reactivation of canceled subtree ", &
               !  new_elem%conf(new_elem%mv_conf)%elem%sub_tree_nr, "elem", new_elem%conf(new_elem%mv_conf)%elem%nr, &
               !  " of existing gt elem ",new_elem%nr,", again calculate NMC steps"
            CASE (mv_type_atom_trans, mv_type_mol_trans, mv_type_mol_rot, &
                  mv_type_proton_reorder)
               CALL cp_abort(__location__, &
                             "reactivated st element has no NMC or MD move type, "// &
                             "but seems to be canceled. Move type"// &
                             cp_to_string(new_elem%conf(new_elem%mv_conf)%elem%move_type))
            CASE DEFAULT
               cpabort("Unknown move type while reactivating subtree element.")
            END SELECT
         ELSE
            !-- if end is found (NOT already existing element), create new elem at the end and if nessecarry new subtree element
            ! set initial values
            CALL allocate_new_global_tree_node(next_el=new_elem, &
                                               nr_temp=tmc_env%params%nr_temp)
            tmc_env%m_env%tree_node_count(0) = tmc_env%m_env%tree_node_count(0) + 1
            new_elem%nr = tmc_env%m_env%tree_node_count(0)
 
            !-- set pointers to and from element one level up
            !-- paste new gt tree node element at right end
            IF (n_acc) THEN
               IF (ASSOCIATED(tmp_elem%acc)) THEN
                  cpabort("creating new subtree element on an occupied acc branch")
               END IF
               tmp_elem%acc => new_elem
            ELSE
               IF (ASSOCIATED(tmp_elem%nacc)) THEN
                  cpabort("creating new subtree element on an occupied nacc branch")
               END IF
               tmp_elem%nacc => new_elem
            END IF
            new_elem%parent => tmp_elem
 
            !-- adopt acceptance flags of elements (old)
            new_elem%conf_n_acc(:) = new_elem%parent%conf_n_acc
            !-- set acceptance flag of modified configuration
            !    depending on the direction of attaching new element
            IF (.NOT. new_elem%parent%swaped) THEN
               ! set the flag for the direction
               !  (shows if the configuration is assumed to be acc or rej)
               new_elem%conf_n_acc(new_elem%parent%conf( &
                                   new_elem%parent%mv_conf)%elem%sub_tree_nr) = n_acc
            ELSE
               !-- in case of swapping the subtree element acceptance do not change
               !-- in case of NOT accepted branch and swapping before,
               !-- search last NOT swaped gt tree node to take configurations
               IF (.NOT. n_acc) THEN
                  DO
                     IF (.NOT. ASSOCIATED(tmp_elem%parent)) EXIT
                     IF (ASSOCIATED(tmp_elem%parent%acc, tmp_elem)) THEN
                        tmp_elem => tmp_elem%parent
                        EXIT
                     END IF
                     tmp_elem => tmp_elem%parent
                     IF (.NOT. tmp_elem%swaped) EXIT
                  END DO
               END IF
            END IF
 
            !-- adapt "old" configurations
            new_elem%conf(:) = tmp_elem%conf(:)
 
            !-- set rnd nr generator and set next conf to change
            CALL tmc_env%rng_stream%set( &
               bg=new_elem%parent%rng_seed(:, :, 1), &
               cg=new_elem%parent%rng_seed(:, :, 2), &
               ig=new_elem%parent%rng_seed(:, :, 3))
            CALL tmc_env%rng_stream%reset_to_next_substream()
            ! the random number for acceptance check
            new_elem%rnd_nr = tmc_env%rng_stream%next()
 
            ! the next configuration index to move
            !rnd = tmc_env%rng_stream%next()
            !new_elem%mv_conf = 1+INT(size(new_elem%conf)*rnd)
            ! one temperature after each other
            new_elem%mv_conf = new_elem%parent%mv_next_conf
            new_elem%mv_next_conf = modulo(new_elem%mv_conf, SIZE(new_elem%conf)) + 1
 
            ! simulated annealing temperature decrease
            new_elem%Temp = tmp_elem%Temp
            IF (n_acc) new_elem%Temp = tmp_elem%Temp*(1 - tmc_env%m_env%temp_decrease)
 
            !-- rnd for swap
            rnd = tmc_env%rng_stream%next()
            rnd2 = tmc_env%rng_stream%next()
            CALL tmc_env%rng_stream%get(bg=new_elem%rng_seed(:, :, 1), &
                                        cg=new_elem%rng_seed(:, :, 2), &
                                        ig=new_elem%rng_seed(:, :, 3))
 
            ! swap moves are not part of the subtree structure,
            !  because existing elements from DIFFERENT subtrees are swaped
            ! -- do swap ?!
            IF (tmc_env%params%move_types%mv_weight(mv_type_swap_conf) >= rnd) THEN
               ! set the index for the swaping element
               !  and the conf to move in next move
               new_elem%mv_next_conf = new_elem%mv_conf
               ! do swap with conf swap_conf and swap_conf+1
               swap_conf = 1 + int((tmc_env%params%nr_temp - 1)*rnd2)
               new_elem%mv_conf = swap_conf
               !-- swaping pointers to subtree elements
               ! exchange the pointer to the sub tree elements
               tree_elem => new_elem%conf(new_elem%mv_conf)%elem
               new_elem%conf(new_elem%mv_conf)%elem => &
                  new_elem%conf(new_elem%mv_conf + 1)%elem
               new_elem%conf(new_elem%mv_conf + 1)%elem => tree_elem
 
               new_elem%stat = status_calculated
               new_elem%swaped = .true.
               new_elem%prob_acc = tmc_env%params%move_types%acc_prob( &
                                   mv_type_swap_conf, new_elem%mv_conf)
               CALL add_to_references(gt_elem=new_elem)
               IF (tmc_env%params%DRAW_TREE) THEN
                  CALL create_global_tree_dot(new_element=new_elem, &
                                              tmc_params=tmc_env%params)
               END IF
               ! nothing to do for the workers
               stat = status_calculated
               keep_on = .false.
            ELSE
 
               !-- considered subtree node can already exist,
               !    calculated somewhere else in the global tree
               !-- so check if new sub tree node exists, if not, create it
               !-- check if considered configuration is assumed to be
               !    on accepted or rejected branch
               IF (new_elem%conf_n_acc(new_elem%conf(new_elem%mv_conf)%elem%sub_tree_nr)) THEN
                  !-- check if child element in ACCEPTED direction already exist
                  IF (ASSOCIATED(new_elem%conf(new_elem%mv_conf)%elem%acc)) THEN
                     new_elem%conf(new_elem%mv_conf)%elem => &
                        new_elem%conf(new_elem%mv_conf)%elem%acc
                     stat = status_calculated
                  ELSE
                     !-- if not exist create new subtree element
                     CALL create_new_subtree_node(act_gt_el=new_elem, &
                                                  tmc_env=tmc_env)
                     IF (tmc_env%params%DRAW_TREE) THEN
                        CALL create_dot(new_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                        conf=new_elem%conf(new_elem%mv_conf)%elem%sub_tree_nr, &
                                        tmc_params=tmc_env%params)
                     END IF
                  END IF
               ELSE
                  !-- check if child element in REJECTED direction already exist
                  IF (ASSOCIATED(new_elem%conf(new_elem%mv_conf)%elem%nacc)) THEN
                     new_elem%conf(new_elem%mv_conf)%elem => &
                        new_elem%conf(new_elem%mv_conf)%elem%nacc
                     stat = status_calculated
                  ELSE
                     !-- if not exist create new subtree element
                     CALL create_new_subtree_node(act_gt_el=new_elem, &
                                                  tmc_env=tmc_env)
                     IF (tmc_env%params%DRAW_TREE) THEN
                        CALL create_dot(new_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                        conf=new_elem%conf(new_elem%mv_conf)%elem%sub_tree_nr, &
                                        tmc_params=tmc_env%params)
                     END IF
                  END IF
               END IF
               ! set approximate probability of acceptance
               !  (initialization with calculated values from
               !  (#acc elem in traj)/(#elem in traj))
               new_elem%prob_acc = tmc_env%params%move_types%acc_prob( &
                                   new_elem%conf(new_elem%mv_conf)%elem%move_type, new_elem%mv_conf)
               ! add refence and dot
               CALL add_to_references(gt_elem=new_elem)
               IF (tmc_env%params%DRAW_TREE) THEN
                  CALL create_global_tree_dot(new_element=new_elem, &
                                              tmc_params=tmc_env%params)
               END IF
            END IF ! swap or no swap
         END IF ! global tree node already exist. Hence the Subtree node also (it is speculative canceled)
      END IF ! keep on (checking and creating)
 
      IF (keep_on) THEN ! status changes
         IF (new_elem%stat == status_accepted_result .OR. &
             new_elem%stat == status_accepted .OR. &
             new_elem%stat == status_rejected .OR. &
             new_elem%stat == status_rejected_result) THEN
            cpabort("selected existing RESULT gt node")
         END IF
         !-- set status of global tree element for decision in master routine
         SELECT CASE (new_elem%conf(new_elem%mv_conf)%elem%stat)
         CASE (status_rejected_result, status_rejected, status_accepted, &
               status_accepted_result, status_calculated)
            ! energy is already calculated
            new_elem%stat = status_calculated
            stat = new_elem%conf(new_elem%mv_conf)%elem%stat
            IF (tmc_env%params%DRAW_TREE) THEN
               CALL create_dot_color(tree_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                     tmc_params=tmc_env%params)
            END IF
         CASE (status_calc_approx_ener)
            new_elem%stat = new_elem%conf(new_elem%mv_conf)%elem%stat
            IF (stat /= status_calculated) THEN
               stat = new_elem%conf(new_elem%mv_conf)%elem%stat
               IF (tmc_env%params%DRAW_TREE) THEN
                  CALL create_dot_color(tree_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                        tmc_params=tmc_env%params)
               END IF
            END IF
         CASE (status_calculate_md, status_calculate_energy, &
               status_calculate_nmc_steps, status_created)
            ! if not already in progress, set status for new task message
            new_elem%stat = new_elem%conf(new_elem%mv_conf)%elem%stat
            IF (stat /= status_calculated) THEN
               stat = new_elem%conf(new_elem%mv_conf)%elem%stat
               IF (tmc_env%params%DRAW_TREE) THEN
                  CALL create_dot_color(tree_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                        tmc_params=tmc_env%params)
               END IF
            END IF
         CASE (status_cancel_ener, status_canceled_ener)
            ! configuration is already created,
            !  but energy has to be calculated (again)
            new_elem%conf(new_elem%mv_conf)%elem%stat = status_created
            new_elem%stat = status_created
            ! creation complete, handle energy calculation at a different position
            !  (for different worker group)
            stat = status_calculated
            IF (tmc_env%params%DRAW_TREE) THEN
               CALL create_dot_color(tree_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                     tmc_params=tmc_env%params)
            END IF
         CASE (status_cancel_nmc, status_canceled_nmc)
            ! reactivation canceled element (but with new global tree element)
            new_elem%conf(new_elem%mv_conf)%elem%stat = &
               status_calculate_nmc_steps
            new_elem%stat = status_calculate_nmc_steps
            stat = new_elem%conf(new_elem%mv_conf)%elem%stat
            reactivation_cc_count = reactivation_cc_count + 1
            IF (tmc_env%params%DRAW_TREE) THEN
               CALL create_dot_color(tree_element=new_elem%conf(new_elem%mv_conf)%elem, &
                                     tmc_params=tmc_env%params)
            END IF
         CASE DEFAULT
            CALL cp_abort(__location__, &
                          "unknown stat "// &
                          cp_to_string(new_elem%conf(new_elem%mv_conf)%elem%stat)// &
                          "of subtree element "// &
                          "for creating new gt element")
         END SELECT
 
         ! set stat TMC_STATUS_WAIT_FOR_NEW_TASK if no new calculation necessary
         !   (energy calculation nodes searched by different routine)
         IF (stat == tmc_status_failed) stat = tmc_status_wait_for_new_task
         IF (stat == status_calculated) stat = tmc_status_wait_for_new_task
      END IF
      ! end the timing
      CALL timestop(handle)
 
   END SUBROUTINE create_new_gt_tree_node
 
! **************************************************************************************************
!> \brief create new subtree element using pointer of global tree
!> \param act_gt_el global tree element
!> \param tmc_env ...
!> \author Mandes 12.2012
! **************************************************************************************************
   SUBROUTINE create_new_subtree_node(act_gt_el, tmc_env)
      TYPE(global_tree_type), POINTER                    :: act_gt_el
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'create_new_subtree_node'
 
      INTEGER                                            :: conf, handle, itmp
      LOGICAL                                            :: mv_rejected, new_subbox
      REAL(kind=dp)                                      :: rnd
      TYPE(tree_type), POINTER                           :: new_elem, parent_elem
 
      NULLIFY (new_elem, parent_elem)
 
      cpassert(ASSOCIATED(act_gt_el))
      cpassert(ASSOCIATED(act_gt_el%conf(act_gt_el%mv_conf)%elem))
      cpassert(ASSOCIATED(tmc_env))
      cpassert(ASSOCIATED(tmc_env%params))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      conf = act_gt_el%mv_conf
      CALL allocate_new_sub_tree_node(tmc_params=tmc_env%params, &
                                      next_el=new_elem, nr_dim=SIZE(act_gt_el%parent%conf(conf)%elem%pos))
 
      !-- node one level up
      parent_elem => act_gt_el%conf(conf)%elem
      new_elem%parent => parent_elem
 
      !-- set initial values
      parent_elem%next_elem_nr = parent_elem%next_elem_nr + 1
      new_elem%nr = parent_elem%next_elem_nr
      new_elem%rng_seed = parent_elem%rng_seed
 
      !-- change to real parent element
      IF (act_gt_el%conf_n_acc(act_gt_el%conf(act_gt_el%mv_conf)%elem%sub_tree_nr)) THEN
         parent_elem%acc => new_elem
      ELSE
         parent_elem%nacc => new_elem
      END IF
 
      !-- real parent node (taking the configuration from)
      ! search parent
      parent_elem => search_parent_element(current=new_elem)
      new_elem%pos(:) = parent_elem%pos(:)
      new_elem%mol(:) = parent_elem%mol(:)
      new_elem%vel(:) = parent_elem%vel(:)
      new_elem%ekin = parent_elem%ekin
      new_elem%e_pot_approx = parent_elem%e_pot_approx
      new_elem%next_elem_nr => parent_elem%next_elem_nr
      new_elem%sub_tree_nr = parent_elem%sub_tree_nr
      new_elem%box_scale = parent_elem%box_scale
      IF (tmc_env%params%task_type == task_type_gaussian_adaptation) THEN
         new_elem%frc(:) = parent_elem%frc(:)
         new_elem%potential = parent_elem%potential
         new_elem%ekin_before_md = parent_elem%ekin_before_md
      ELSE
         new_elem%potential = 97589.0_dp
      END IF
 
      ! set new substream of random number generator
      CALL tmc_env%rng_stream%set( &
         bg=new_elem%rng_seed(:, :, 1), &
         cg=new_elem%rng_seed(:, :, 2), &
         ig=new_elem%rng_seed(:, :, 3))
      CALL tmc_env%rng_stream%reset_to_next_substream()
 
      ! set the temperature for the NMC moves
      rnd = tmc_env%rng_stream%next()
      IF (tmc_env%params%NMC_inp_file /= "") THEN
         new_elem%temp_created = int(tmc_env%params%nr_temp*rnd) + 1
      ELSE
         new_elem%temp_created = act_gt_el%mv_conf
      END IF
 
      ! rnd nr for selecting move
      rnd = tmc_env%rng_stream%next()
      !-- set move type
      new_elem%move_type = select_random_move_type( &
                           move_types=tmc_env%params%move_types, &
                           rnd=rnd)
      CALL tmc_env%rng_stream%get( &
         bg=new_elem%rng_seed(:, :, 1), &
         cg=new_elem%rng_seed(:, :, 2), &
         ig=new_elem%rng_seed(:, :, 3))
 
      ! move is only done by the master,
      !  when standard MC moves with single potential are done
      ! the Nested Monte Carlo routine needs the old configuration
      !  to see if change is accepted
      SELECT CASE (new_elem%move_type)
      CASE (mv_type_md)
         ! velocity change have to be done on workers,
         !  because of velocity change for NMC acceptance check
         new_elem%stat = status_calculate_md
         ! set the temperature for creating MD
         new_elem%temp_created = act_gt_el%mv_conf
         !-- set the subbox (elements in subbox)
         CALL elements_in_new_subbox(tmc_params=tmc_env%params, &
                                     rng_stream=tmc_env%rng_stream, elem=new_elem, &
                                     nr_of_sub_box_elements=itmp)
         ! the move is performed on a worker group
      CASE (mv_type_nmc_moves)
         new_elem%stat = status_calculate_nmc_steps
         !-- set the subbox (elements in subbox)
         CALL elements_in_new_subbox(tmc_params=tmc_env%params, &
                                     rng_stream=tmc_env%rng_stream, elem=new_elem, &
                                     nr_of_sub_box_elements=itmp)
         ! the move is performed on a worker group
         ! the following moves new no force_env and can be performed on the master directly
      CASE (mv_type_atom_trans, mv_type_atom_swap, mv_type_mol_trans, &
            mv_type_mol_rot, mv_type_proton_reorder, &
            mv_type_volume_move)
         new_subbox = .true.
         ! volume move on whole cell
         IF (new_elem%move_type == mv_type_volume_move) THEN
            new_subbox = .false.
         END IF
         CALL change_pos(tmc_params=tmc_env%params, &
                         move_types=tmc_env%params%move_types, &
                         rng_stream=tmc_env%rng_stream, elem=new_elem, &
                         mv_conf=conf, new_subbox=new_subbox, &
                         move_rejected=mv_rejected)
         IF (mv_rejected) THEN
            new_elem%potential = huge(new_elem%potential)
            new_elem%e_pot_approx = huge(new_elem%e_pot_approx)
            new_elem%stat = status_calculated
         ELSE
            new_elem%stat = status_created
            IF (tmc_env%params%NMC_inp_file /= "") THEN
               new_elem%stat = status_calc_approx_ener
            END IF
         END IF
      CASE (mv_type_gausian_adapt)
         ! still could be implemented
      CASE DEFAULT
         CALL cp_abort(__location__, &
                       "unknown move type ("//cp_to_string(new_elem%move_type)// &
                       "), while creating subtree element.")
      END SELECT
      act_gt_el%conf(act_gt_el%mv_conf)%elem => new_elem
 
      ! end the timing
      CALL timestop(handle)
      cpassert(ASSOCIATED(act_gt_el%conf(act_gt_el%mv_conf)%elem))
   END SUBROUTINE create_new_subtree_node
 
   !============================================================================
   ! tree node deallocation
   !============================================================================
! **************************************************************************************************
!> \brief prepares for deallocation of global tree element
!>        (checks status and set pointers of neighboring elements)
!> \param gt_ptr the global tree element
!> \param draw if present, changes the coleor in the dot file
!> \param tmc_env tmc environment
!> \author Mandes 12.2012
! **************************************************************************************************
   SUBROUTINE remove_gt_elem(gt_ptr, draw, tmc_env)
      TYPE(global_tree_type), POINTER                    :: gt_ptr
      LOGICAL, OPTIONAL                                  :: draw
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER                        :: routinen = 'remove_gt_elem'
 
      INTEGER                                            :: handle
 
      cpassert(ASSOCIATED(gt_ptr))
      cpassert(ASSOCIATED(tmc_env))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      CALL remove_gt_references(gt_ptr=gt_ptr, tmc_env=tmc_env)
 
      ! set status and draw in tree
      IF ((gt_ptr%stat == status_accepted_result) .OR. (gt_ptr%stat == status_rejected_result)) THEN
         gt_ptr%stat = status_deleted_result
      ELSE
         gt_ptr%stat = status_deleted
      END IF
      IF (tmc_env%params%DRAW_TREE .AND. PRESENT(draw)) THEN
         CALL create_global_tree_dot_color(gt_tree_element=gt_ptr, tmc_params=tmc_env%params)
      END IF
 
      !remove pointer from tree parent
      IF (ASSOCIATED(gt_ptr%parent)) THEN
         IF (ASSOCIATED(gt_ptr%parent%acc, gt_ptr)) THEN
            gt_ptr%parent%acc => null()
         END IF
         IF (ASSOCIATED(gt_ptr%parent%nacc, gt_ptr)) THEN
            gt_ptr%parent%nacc => null()
         END IF
      END IF
 
      !remove pointer from tree childs
      IF (ASSOCIATED(gt_ptr%acc)) THEN
         gt_ptr%acc%parent => null()
      END IF
 
      IF (ASSOCIATED(gt_ptr%nacc)) THEN
         gt_ptr%nacc%parent => null()
      END IF
 
      CALL deallocate_global_tree_node(gt_elem=gt_ptr)
      ! end the timing
      CALL timestop(handle)
 
      cpassert(.NOT. ASSOCIATED(gt_ptr))
   END SUBROUTINE remove_gt_elem
 
! **************************************************************************************************
!> \brief prepares for deallocation of sub tree element
!>        (checks status and set pointers of neighboring elements)
!> \param ptr the sub tree element
!> \param draw if present, changes the coleor in the dot file
!> \param tmc_env tmc environment
!> \author Mandes 12.2012
! **************************************************************************************************
   SUBROUTINE remove_st_elem(ptr, draw, tmc_env)
      TYPE(tree_type), POINTER                           :: ptr
      LOGICAL, OPTIONAL                                  :: draw
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER                        :: routinen = 'remove_st_elem'
 
      INTEGER                                            :: handle
      LOGICAL                                            :: ready
 
      ready = .true.
      cpassert(ASSOCIATED(ptr))
      cpassert(ASSOCIATED(tmc_env))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      ! if there is still e reference to a global tree pointer, do not deallocate element
      IF (ASSOCIATED(ptr%gt_nodes_references)) THEN
         IF (ASSOCIATED(ptr%parent)) THEN
            CALL cp_warn(__location__, &
                         "try to deallocate subtree element"// &
                         cp_to_string(ptr%sub_tree_nr)//cp_to_string(ptr%nr)// &
                         " still with global tree element references e.g."// &
                         cp_to_string(ptr%gt_nodes_references%gt_elem%nr))
         END IF
         cpassert(ASSOCIATED(ptr%gt_nodes_references%gt_elem))
      ELSE
         SELECT CASE (ptr%stat)
            ! if element is still in progress, do not delete, wait for responding
         CASE (status_calculate_energy, &
               status_calculate_nmc_steps, status_calculate_md)
            ! in case of speculative canceling: should be already canceled
            !  try to deallocate subtree element (still in progress)
            cpassert(tmc_env%params%SPECULATIVE_CANCELING)
         CASE (status_cancel_nmc, status_cancel_ener)
            ! do not return in case of finalizing (do not wait for canceling receipt)
            IF (PRESENT(draw)) ready = .false.
         CASE DEFAULT
         END SELECT
 
         ! check if real top to bottom or bottom to top deallocation (no middle element deallocation)
         IF (ASSOCIATED(ptr%parent) .AND. &
             (ASSOCIATED(ptr%acc) .OR. ASSOCIATED(ptr%nacc))) THEN
            cpabort("Invalid association state of parent element")
         END IF
 
         IF (ready) THEN
            ! set status and draw in tree
            IF ((ptr%stat == status_accepted_result) .OR. &
                (ptr%stat == status_rejected_result)) THEN
               ptr%stat = status_deleted_result
            ELSE
               ptr%stat = status_deleted
            END IF
            IF (tmc_env%params%DRAW_TREE .AND. PRESENT(draw)) THEN
               CALL create_dot_color(tree_element=ptr, tmc_params=tmc_env%params)
            END IF
 
            !remove pointer from tree parent
            IF (ASSOCIATED(ptr%parent)) THEN
               IF (ASSOCIATED(ptr%parent%acc, ptr)) ptr%parent%acc => null()
               IF (ASSOCIATED(ptr%parent%nacc, ptr)) ptr%parent%nacc => null()
            END IF
 
            !remove pointer from tree childs
            IF (ASSOCIATED(ptr%acc)) ptr%acc%parent => null()
            IF (ASSOCIATED(ptr%nacc)) ptr%nacc%parent => null()
 
            ! deallocate
            CALL deallocate_sub_tree_node(tree_elem=ptr)
         END IF
      END IF
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE remove_st_elem
 
! **************************************************************************************************
!> \brief deletes the no more used global tree nodes beside the result nodes
!>        from begin_ptr to end_ptr
!> \param begin_ptr start of the tree region to be cleaned
!> \param end_ptr end of the tree region to be cleaned
!> \param removed retun value if brance is clean
!> \param tmc_env tmc environment
!> \author Mandes 12.2012
! **************************************************************************************************
   RECURSIVE SUBROUTINE remove_unused_g_tree(begin_ptr, end_ptr, removed, tmc_env)
      TYPE(global_tree_type), POINTER                    :: begin_ptr, end_ptr
      LOGICAL                                            :: removed
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'remove_unused_g_tree'
 
      INTEGER                                            :: handle
      LOGICAL                                            :: acc_removed, nacc_removed
      TYPE(global_tree_type), POINTER                    :: acc_ptr, nacc_ptr, tmp_ptr
 
      NULLIFY (acc_ptr, nacc_ptr, tmp_ptr)
 
      cpassert(ASSOCIATED(begin_ptr))
      cpassert(ASSOCIATED(end_ptr))
      cpassert(ASSOCIATED(tmc_env))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      removed = .false.
      acc_removed = .false.
      nacc_removed = .false.
 
      IF (.NOT. ASSOCIATED(begin_ptr, end_ptr)) THEN
         !-- go until the ends ot he tree, to deallocate revese
         !-- check if child nodes exist and possibly deallocate child node
         IF (ASSOCIATED(begin_ptr%acc)) THEN
            acc_ptr => begin_ptr%acc
            CALL remove_unused_g_tree(acc_ptr, end_ptr, acc_removed, tmc_env)
         ELSE
            acc_removed = .true.
         END IF
         IF (ASSOCIATED(begin_ptr%nacc)) THEN
            nacc_ptr => begin_ptr%nacc
            CALL remove_unused_g_tree(nacc_ptr, end_ptr, nacc_removed, tmc_env)
         ELSE
            nacc_removed = .true.
         END IF
 
         !-- deallocate node if no child node exist
         IF (acc_removed .AND. nacc_removed) THEN
            SELECT CASE (begin_ptr%stat)
            CASE (status_accepted, status_rejected, status_calculated, status_created, &
                  status_calculate_energy, status_calculate_md, status_calculate_nmc_steps, status_calc_approx_ener, &
                  status_cancel_nmc, status_cancel_ener, status_canceled_nmc, status_canceled_ener)
               ! delete references, cancel elements calculation and deallocate global tree element
               tmp_ptr => begin_ptr
 
               CALL remove_gt_elem(gt_ptr=tmp_ptr, draw=.true., tmc_env=tmc_env)
               IF (.NOT. ASSOCIATED(tmp_ptr)) removed = .true.
            CASE (status_accepted_result, status_rejected_result)
            CASE DEFAULT
               CALL cp_abort(__location__, &
                             "try to dealloc unused tree element with status of begin element" &
                             //cp_to_string(begin_ptr%stat))
            END SELECT
         END IF
      END IF
      ! end the timing
      CALL timestop(handle)
      cpassert(ASSOCIATED(end_ptr))
   END SUBROUTINE remove_unused_g_tree
 
! **************************************************************************************************
!> \brief deletes the no more used sub tree nodes beside the result nodes
!>        from begin_ptr to end_ptr
!> \param begin_ptr start of the tree region to be cleaned
!> \param end_ptr end of the tree region to be cleaned
!> \param working_elem_list ...
!> \param removed retun value if brance is clean
!> \param tmc_env tmc environment
!> \author Mandes 12.2012
! **************************************************************************************************
   RECURSIVE SUBROUTINE remove_unused_s_tree(begin_ptr, end_ptr, working_elem_list, &
                                             removed, tmc_env)
      TYPE(tree_type), POINTER                           :: begin_ptr
      TYPE(tree_type), INTENT(IN), POINTER               :: end_ptr
      TYPE(elem_array_type), DIMENSION(:), POINTER       :: working_elem_list
      LOGICAL                                            :: removed
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'remove_unused_s_tree'
 
      INTEGER                                            :: handle, i
      LOGICAL                                            :: acc_removed, nacc_removed, remove_this
      TYPE(tree_type), POINTER                           :: acc_ptr, nacc_ptr, tmp_ptr
 
      NULLIFY (acc_ptr, nacc_ptr, tmp_ptr)
      remove_this = .false.
      removed = .false.
      acc_removed = .false.
      nacc_removed = .false.
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      cpassert(ASSOCIATED(begin_ptr))
      cpassert(ASSOCIATED(end_ptr))
      cpassert(ASSOCIATED(working_elem_list))
      cpassert(ASSOCIATED(tmc_env))
 
      !-- if element is last checked in trajectory, go back
      IF (.NOT. ASSOCIATED(begin_ptr, end_ptr)) THEN
         !-- go until the ends on the tree, to deallocate revesely
         !-- check if child nodes exist and possibly deallocate child node
         IF (ASSOCIATED(begin_ptr%acc)) THEN
            acc_ptr => begin_ptr%acc
            CALL remove_unused_s_tree(acc_ptr, end_ptr, working_elem_list, &
                                      acc_removed, tmc_env)
         ELSE
            acc_removed = .true.
         END IF
         IF (ASSOCIATED(begin_ptr%nacc)) THEN
            nacc_ptr => begin_ptr%nacc
            CALL remove_unused_s_tree(nacc_ptr, end_ptr, working_elem_list, &
                                      nacc_removed, tmc_env)
         ELSE
            nacc_removed = .true.
         END IF
 
         !IF (DEBUG>=20) WRITE(tmc_out_file_nr,*)"try to dealloc: node", begin_ptr%nr," sides are removed: ", &
         !                                          acc_removed, nacc_removed
 
         !-- deallocate node if NO child node exist
         ! unused trajectory is deleted when cleaned part is updated
         IF (acc_removed .AND. nacc_removed) THEN
            SELECT CASE (begin_ptr%stat)
            CASE (status_canceled_nmc, status_canceled_ener)
               remove_this = .true.
            CASE (status_accepted, status_rejected, status_calculated, &
                  status_accepted_result, status_rejected_result, status_created)
               remove_this = .true.
               ! not to cancel, because still in progress
            CASE (status_calculate_energy, status_calculate_nmc_steps, &
                  status_calculate_md, status_cancel_nmc, status_cancel_ener, &
                  status_calc_approx_ener)
               remove_this = .false.
               ! -- delete when calculation is finished or aborted
               ! removed should still be .FALSE.
            CASE DEFAULT
               CALL cp_abort(__location__, &
                             "unknown status "//cp_to_string(begin_ptr%stat)// &
                             "of sub tree element "// &
                             cp_to_string(begin_ptr%sub_tree_nr)//" "// &
                             cp_to_string(begin_ptr%nr))
            END SELECT
 
            ! delete element
            IF (remove_this) THEN
               !-- mark as deleted and draw it in tree
               IF (.NOT. ASSOCIATED(begin_ptr%parent)) THEN
                  CALL cp_abort(__location__, &
                                "try to remove unused subtree element "// &
                                cp_to_string(begin_ptr%sub_tree_nr)//" "// &
                                cp_to_string(begin_ptr%nr)// &
                                " but parent does not exist")
               END IF
               tmp_ptr => begin_ptr
               ! check if a working group is still working on this element
               removed = .true.
               DO i = 1, SIZE(working_elem_list(:))
                  IF (ASSOCIATED(working_elem_list(i)%elem)) THEN
                     IF (ASSOCIATED(working_elem_list(i)%elem, tmp_ptr)) THEN
                        removed = .false.
                     END IF
                  END IF
               END DO
               IF (removed) THEN
                  !IF (DEBUG>=20) WRITE(tmc_out_file_nr,*)"deallocation of node ", begin_ptr%nr, "with status ", begin_ptr%stat
                  ! if all groups are finished with this element, we can deallocate
                  CALL remove_st_elem(ptr=tmp_ptr, draw=.true., tmc_env=tmc_env)
                  IF (.NOT. ASSOCIATED(tmp_ptr)) THEN
                     removed = .true.
                  ELSE
                     removed = .false.
                  END IF
               END IF
            END IF
         END IF
      END IF
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE remove_unused_s_tree
 
! **************************************************************************************************
!> \brief deallocates all result nodes (remaining Markov Chain)
!>        from the tree root to the end of clean tree of the global tree
!> \param end_of_clean_tree ...
!> \param actual_ptr ...
!> \param tmc_env TMC environment for deallocation
!> \author Mandes 12.2012
! **************************************************************************************************
   RECURSIVE SUBROUTINE remove_result_g_tree(end_of_clean_tree, actual_ptr, &
                                             tmc_env)
      TYPE(global_tree_type), POINTER                    :: end_of_clean_tree, actual_ptr
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'remove_result_g_tree'
 
      INTEGER                                            :: handle
      TYPE(global_tree_type), POINTER                    :: tmp_ptr
 
      cpassert(ASSOCIATED(end_of_clean_tree))
      cpassert(ASSOCIATED(actual_ptr))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      !-- going up to the head ot the subtree
      IF (ASSOCIATED(actual_ptr%parent)) THEN
         CALL remove_result_g_tree(end_of_clean_tree=end_of_clean_tree, &
                                   actual_ptr=actual_ptr%parent, &
                                   tmc_env=tmc_env)
      END IF
      !-- new tree head has no parent
      IF (.NOT. ASSOCIATED(actual_ptr, end_of_clean_tree)) THEN
         !-- deallocate node
         !IF(DEBUG>=20) WRITE(tmc_out_file_nr,*)"dealloc gt result tree element: ",actual_ptr%nr
         tmp_ptr => actual_ptr
         CALL remove_gt_elem(gt_ptr=tmp_ptr, draw=.true., tmc_env=tmc_env)
         actual_ptr => tmp_ptr
      END IF
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE remove_result_g_tree
 
! **************************************************************************************************
!> \brief deallocates all result nodes (remaining Markov Chain)
!>        from the tree root to the end of clean tree of one sub tree
!>        top to buttom deallocation
!> \param end_of_clean_tree ...
!> \param actual_ptr ...
!> \param tmc_env TMC environment for deallocation
!> \author Mandes 12.2012
! **************************************************************************************************
   RECURSIVE SUBROUTINE remove_result_s_tree(end_of_clean_tree, actual_ptr, &
                                             tmc_env)
      TYPE(tree_type), POINTER                           :: end_of_clean_tree, actual_ptr
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER :: routinen = 'remove_result_s_tree'
 
      INTEGER                                            :: handle
      TYPE(tree_type), POINTER                           :: tmp_ptr
 
      cpassert(ASSOCIATED(end_of_clean_tree))
      cpassert(ASSOCIATED(actual_ptr))
      cpassert(ASSOCIATED(tmc_env))
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      !-- going up to the head ot the subtree
      IF (ASSOCIATED(actual_ptr%parent)) THEN
         CALL remove_result_s_tree(end_of_clean_tree, actual_ptr%parent, &
                                   tmc_env)
      END IF
 
      !-- new tree head has no parent
      IF (.NOT. ASSOCIATED(actual_ptr, end_of_clean_tree)) THEN
         ! in trajectory just one direction should exist
         cpassert(.NOT. (ASSOCIATED(actual_ptr%acc) .AND. ASSOCIATED(actual_ptr%nacc)))
         ! the parent should be deleted already, but global tree is allocated to the second last accepted, &
         !   hence there could be still a reference to an element...
         IF (.NOT. ASSOCIATED(actual_ptr%parent)) THEN
            !-- deallocate node
            tmp_ptr => actual_ptr
            CALL remove_st_elem(ptr=tmp_ptr, draw=.true., tmc_env=tmc_env)
            actual_ptr => tmp_ptr
         END IF
      END IF
      ! end the timing
      CALL timestop(handle)
   END SUBROUTINE remove_result_s_tree
 
! **************************************************************************************************
!> \brief deallocates the no more used tree nodes beside the result nodes
!>        from begin_ptr to end_ptr
!>        in global and subtrees
!> \param working_elem_list list of actual calculating elements for canceling
!> \param tmc_env TMC environment
!> \author Mandes 12.2012
! **************************************************************************************************
   SUBROUTINE remove_all_trees(working_elem_list, tmc_env)
      TYPE(elem_array_type), DIMENSION(:), POINTER       :: working_elem_list
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      CHARACTER(LEN=*), PARAMETER                        :: routinen = 'remove_all_trees'
 
      INTEGER                                            :: handle, i, tree
      LOGICAL                                            :: change_trajec, flag
      TYPE(global_tree_type), POINTER                    :: tmp_gt_ptr
      TYPE(tree_type), POINTER                           :: last_acc_st_elem, tmp_ptr
 
      NULLIFY (last_acc_st_elem, tmp_ptr, tmp_gt_ptr)
 
      cpassert(ASSOCIATED(working_elem_list))
      cpassert(ASSOCIATED(tmc_env))
      cpassert(ASSOCIATED(tmc_env%m_env))
      cpassert(ASSOCIATED(tmc_env%m_env%gt_act))
      cpassert(ASSOCIATED(tmc_env%m_env%gt_clean_end))
      cpassert(ASSOCIATED(tmc_env%m_env%result_list))
      cpassert(ASSOCIATED(tmc_env%m_env%st_clean_ends))
 
      flag = .false.
      change_trajec = .false.
 
      ! start the timing
      CALL timeset(routinen, handle)
 
      !-- deallocate unused pt tree
      CALL remove_unused_g_tree(begin_ptr=tmc_env%m_env%gt_clean_end, &
                                end_ptr=tmc_env%m_env%gt_act, removed=flag, &
                                tmc_env=tmc_env)
      tmp_gt_ptr => tmc_env%m_env%gt_clean_end
      CALL search_end_of_clean_g_tree(last_acc=tmc_env%m_env%gt_clean_end, &
                                      tree_ptr=tmp_gt_ptr)
      !-- deallocate unused pt trajectory tree elements
      IF (tmc_env%params%USE_REDUCED_TREE) THEN
         tmp_gt_ptr => tmc_env%m_env%gt_clean_end
         CALL remove_result_g_tree(end_of_clean_tree=tmc_env%m_env%gt_clean_end, &
                                   actual_ptr=tmp_gt_ptr, tmc_env=tmc_env)
 
         !check if something changed, if not no deallocation of result subtree necessary
         IF (.NOT. ASSOCIATED(tmc_env%m_env%gt_head, tmc_env%m_env%gt_clean_end)) THEN
            change_trajec = .true.
         END IF
         tmc_env%m_env%gt_head => tmc_env%m_env%gt_clean_end
         cpassert(.NOT. ASSOCIATED(tmc_env%m_env%gt_head%parent))
         !IF (DEBUG>=20) WRITE(tmc_out_file_nr,*)"new head of pt tree is ",tmc_env%m_env%gt_head%nr
      END IF
 
      !-- deallocate the subtrees
      ! do for all temperatures respectively all subtrees
      DO tree = 1, tmc_env%params%nr_temp
         ! get last checked element in trajectory related to the subtree (resultlist order is NOT subtree order)
         conf_loop: DO i = 1, SIZE(tmc_env%m_env%result_list)
            last_acc_st_elem => tmc_env%m_env%result_list(i)%elem
            IF (last_acc_st_elem%sub_tree_nr == tree) THEN
               EXIT conf_loop
            END IF
         END DO conf_loop
         cpassert(last_acc_st_elem%sub_tree_nr == tree)
         CALL remove_unused_s_tree(begin_ptr=tmc_env%m_env%st_clean_ends(tree)%elem, &
                                   end_ptr=last_acc_st_elem, working_elem_list=working_elem_list, &
                                   removed=flag, tmc_env=tmc_env)
         CALL search_end_of_clean_tree(tree_ptr=tmc_env%m_env%st_clean_ends(tree)%elem, &
                                       last_acc=last_acc_st_elem)
      END DO
      !-- deallocate the trajectory subtree elements
      IF (tmc_env%params%USE_REDUCED_TREE .AND. change_trajec) THEN
         DO tree = 1, tmc_env%params%nr_temp
            tmp_ptr => tmc_env%m_env%st_clean_ends(tree)%elem
            cpassert(tmp_ptr%sub_tree_nr == tree)
            CALL remove_result_s_tree(end_of_clean_tree=tmc_env%m_env%st_clean_ends(tree)%elem, &
                                      actual_ptr=tmp_ptr, tmc_env=tmc_env)
            tmc_env%m_env%st_heads(tree)%elem => tmc_env%m_env%st_clean_ends(tree)%elem
            !IF(DEBUG>=20) &
            !  WRITE(tmc_out_file_nr,*)"new head of tree ",tree," is ",&
            !        tmc_env%m_env%st_heads(tree)%elem%nr
         END DO
      END IF
 
      ! end the timing
      CALL timestop(handle)
      cpassert(ASSOCIATED(tmc_env%m_env%gt_act))
      cpassert(ASSOCIATED(tmc_env%m_env%gt_clean_end))
   END SUBROUTINE remove_all_trees
 
! **************************************************************************************************
!> \brief deallocates the whole global tree, to clean up
!> \param begin_ptr pointer to global tree head
!> \param removed flag, if the this element is removed
!> \param tmc_env ...
!> \author Mandes 01.2013
! **************************************************************************************************
   RECURSIVE SUBROUTINE dealloc_whole_g_tree(begin_ptr, removed, tmc_env)
      TYPE(global_tree_type), POINTER                    :: begin_ptr
      LOGICAL                                            :: removed
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      LOGICAL                                            :: acc_removed, nacc_removed
      TYPE(global_tree_type), POINTER                    :: acc_ptr, nacc_ptr, tmp_ptr
 
      cpassert(ASSOCIATED(begin_ptr))
      cpassert(ASSOCIATED(tmc_env))
 
      IF (ASSOCIATED(begin_ptr%acc)) THEN
         acc_ptr => begin_ptr%acc
         CALL dealloc_whole_g_tree(acc_ptr, acc_removed, tmc_env)
      ELSE
         acc_removed = .true.
      END IF
      IF (ASSOCIATED(begin_ptr%nacc)) THEN
         nacc_ptr => begin_ptr%nacc
         CALL dealloc_whole_g_tree(nacc_ptr, nacc_removed, tmc_env)
      ELSE
         nacc_removed = .true.
      END IF
 
      !-- deallocate node if no child node exist
      IF (acc_removed .AND. nacc_removed) THEN
         CALL search_and_remove_reference_in_list(gt_ptr=begin_ptr, &
                                                  elem=begin_ptr%conf(begin_ptr%mv_conf)%elem, tmc_env=tmc_env)
         tmp_ptr => begin_ptr
         CALL remove_gt_elem(gt_ptr=tmp_ptr, draw=.false., tmc_env=tmc_env)
         !CALL deallocate_global_tree_node(gt_elem=tmp_ptr)
         removed = .true.
      END IF
   END SUBROUTINE dealloc_whole_g_tree
! **************************************************************************************************
!> \brief deallocates the whole sub tree, to clean up
!> \param begin_ptr pointer to sub tree head
!> \param removed flag, if the this element is removed
!> \param tmc_params ...
!> \author Mandes 01.2013
! **************************************************************************************************
   RECURSIVE SUBROUTINE dealloc_whole_subtree(begin_ptr, removed, tmc_params)
      TYPE(tree_type), POINTER                           :: begin_ptr
      LOGICAL                                            :: removed
      TYPE(tmc_param_type), POINTER                      :: tmc_params
 
      LOGICAL                                            :: acc_removed, nacc_removed
      TYPE(tree_type), POINTER                           :: acc_ptr, nacc_ptr, tmp_ptr
 
      cpassert(ASSOCIATED(begin_ptr))
      cpassert(ASSOCIATED(tmc_params))
 
      IF (ASSOCIATED(begin_ptr%acc)) THEN
         acc_ptr => begin_ptr%acc
         CALL dealloc_whole_subtree(acc_ptr, acc_removed, tmc_params)
      ELSE
         acc_removed = .true.
      END IF
      IF (ASSOCIATED(begin_ptr%nacc)) THEN
         nacc_ptr => begin_ptr%nacc
         CALL dealloc_whole_subtree(nacc_ptr, nacc_removed, tmc_params)
      ELSE
         nacc_removed = .true.
      END IF
 
      !-- deallocate node if no child node exist
      IF (acc_removed .AND. nacc_removed) THEN
         tmp_ptr => begin_ptr
         CALL deallocate_sub_tree_node(tree_elem=begin_ptr)
         removed = .true.
      END IF
   END SUBROUTINE dealloc_whole_subtree
 
   !============================================================================
   ! finalizing module (deallocating everything)
   !============================================================================
! **************************************************************************************************
!> \brief deallocating every tree node of every trees (clean up)
!> \param tmc_env TMC environment structure
!> \author Mandes 01.2013
! **************************************************************************************************
   SUBROUTINE finalize_trees(tmc_env)
      TYPE(tmc_env_type), POINTER                        :: tmc_env
 
      INTEGER                                            :: i
      LOGICAL                                            :: flag
      TYPE(global_tree_type), POINTER                    :: global_tree
 
      cpassert(ASSOCIATED(tmc_env))
      cpassert(ASSOCIATED(tmc_env%m_env))
 
      global_tree => tmc_env%m_env%gt_act
      !-- deallocate pt tree
      ! start with searching the head
      DO WHILE (ASSOCIATED(global_tree%parent))
         global_tree => global_tree%parent
      END DO
      CALL dealloc_whole_g_tree(begin_ptr=global_tree, removed=flag, &
                                tmc_env=tmc_env)
 
      !-- deallocate subtrees
      trees_loop: DO i = 1, SIZE(tmc_env%m_env%st_clean_ends(:))
         DO WHILE (ASSOCIATED(tmc_env%m_env%st_clean_ends(i)%elem%parent))
            tmc_env%m_env%st_clean_ends(i)%elem => &
               tmc_env%m_env%st_clean_ends(i)%elem%parent
         END DO
         CALL dealloc_whole_subtree(begin_ptr=tmc_env%m_env%st_clean_ends(i)%elem, &
                                    removed=flag, tmc_params=tmc_env%params)
      END DO trees_loop
      DEALLOCATE (tmc_env%params%atoms)
   END SUBROUTINE finalize_trees
 
END MODULE tmc_tree_build