anchor.diff:    type(profile_t) :: vx
     type(h5md_element_t) :: elem_tz, elem_tz_count
     type(h5md_element_t) :: elem_rhoz
  -  double precision, allocatable :: v_xz(:,:,:), v_xyz(:,:,:)
  -  integer, allocatable :: v_xz_count(:,:), v_xyz_count(:,:)
  +  double precision, allocatable :: v_xz(:,:,:), v_xyz(:,:,:,:)
  +  integer, allocatable :: v_xz_count(:,:), v_xyz_count(:,:,:)
     type(h5md_element_t) :: v_xz_el
   
     integer :: rho
  
positive.code: 
    subroutine div_vxyz()
  
      integer :: i, j
      do i = 1, L(1)
         do j = 1, L(2)
            do k = 1, L(3)
  
negative.code:   dt = tau / N_MD_steps
    N_loop = PTread_i(config, 'N_loop')
    N_therm = PTread_i(config, 'N_therm')
    vxz_interval = PTread_i(config, 'vxz_interval')
  
    wall_t = PTread_dvec(config, 'wall_T', 2)
    T = PTread_d(config, 'T')
  