sample_get_particle_dt Function

  function sample_get_particle_dt(partp, end_time) result(dt_p)
    use mod_global_parameters
    use mod_geometry
    use mod_usr_methods, only: usr_particle_position
    type(particle_ptr), intent(in) :: partp
    double precision, intent(in)   :: end_time
    double precision               :: dt_p
    integer                        :: ipart, iipart, nout, id
    double precision               :: tout, dt_cfl
    double precision               :: v(1:ndir), xp(3), told, tnew

    if (const_dt_particles > 0) then
      dt_p = const_dt_particles
      return
    end if

    dt_p = dtsave_particles

    ! Make sure the user-defined particle movement doesn't break communication
    if (associated(usr_particle_position)) then
      xp = partp%self%x
      told = partp%self%time
      tnew = told+dt_p
      call usr_particle_position(xp, partp%self%index, told, tnew)
      do while (.not. point_in_igrid_ghostc(xp,partp%igrid,1))
        dt_p = dt_p/10.d0
        xp = partp%self%x
        tnew = told+dt_p
        call usr_particle_position(xp, partp%self%index, told, tnew)
      end do
    end if

    ! Make sure we don't advance beyond end_time
    call limit_dt_endtime(end_time - partp%self%time, dt_p)

  end function sample_get_particle_dt