fv_frame_consistency_residual
=============================

.. py:function:: t3toolbox.backend.fv_operations.fv_frame_consistency_residual(frame)

   .. code-block:: python

      def fv_frame_consistency_residual(
              frame: typ.Tuple[
                  typ.Sequence[NDArray],  # up_tucker_cores
                  typ.Sequence[NDArray],  # down_tt_cores
                  typ.Sequence[NDArray],  # left_tt_cores
                  typ.Sequence[NDArray],  # right_tt_cores
              ],
      ) -> NDArray:  # shape = stack_shape (per stack element; scalar/0-d when unstacked)


   Relative Frobenius mismatch between the left- and right-canonical reconstructions of the base
   point (``up`` over ``left`` vs ``up`` over ``right``), **per stack element**.

   Returns ``||left - right|| / max(1, ||right||)`` over the dense **mode** axes (the norm is reduced over
   the non-stack axes, so the result has shape ``stack_shape``); a caller thresholds it (``<= rtol``) for a
   per-element boolean consistency test. EXPENSIVE -- densifies both reconstructions.