anchor.diff:  
       call h5screate_simple_f(rank, dims, s_id, h5_error, max_dims)
       call h5pcreate_f(H5P_DATASET_CREATE_F, plist, h5_error)
  -    if (compress) then
  +    if (compress_var) then
          call h5zfilter_avail_f(H5Z_FILTER_SZIP_F,sz_avail, h5_error)
          if (.not.sz_avail) stop 'SZIP filter not available'
          CALL h5zget_filter_info_f(H5Z_FILTER_SZIP_F, filter_info, h5_error)
  
positive.code:        stop
      end if
      
      if (present(compress_in)) then
         compress = compress_in
      else
         compress = .false.
      end if
  
      if (present(group_name)) then
  
negative.code:     character(len=*), intent(in), optional :: group_name
      logical, intent(in), optional :: species_react
      character(len=*), intent(in), optional :: link_from
      logical, intent(in), optional :: compress
      
      character(len=128) :: path
      integer :: rank
      integer(HSIZE_T) :: dims(3), max_dims(3), chunk_dims(3)
      integer(HID_T) :: traj_g_id, g_id, s_id, plist
      logical :: sz_avail, sz_encode, compress_var
      integer :: filter_info
  
      if ( (trajectory_name .ne. 'position') .and. (trajectory_name .ne. 'velocity') &
  