anchor.diff:    dt = tau / N_MD_steps
     N_loop = PTread_i(config, 'N_loop')
     N_therm = PTread_i(config, 'N_therm')
  -  vxz_interval = PTread(config, 'vxz_interval')
  +  vxz_interval = PTread_i(config, 'vxz_interval')
   
     wall_t = PTread_dvec(config, 'wall_T', 2)
     T = PTread_d(config, 'T')
  
positive.code:   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(:,:)
    type(h5md_element_t) :: v_xz_el
  
    integer :: rho
  
negative.code: 
    subroutine div_vxyz()
  
      integer :: i, j, k
      do i = 1, L(1)
         do j = 1, L(2)
            do k = 1, L(3)
  