* \param Criterion A criterion to choose a diagonal for splitting.
* \return 1 if 1-3 diagonal is better, 2 if 2-4
* diagonal is better, 0 if error occurs.
* \param Criterion A criterion to choose a diagonal for splitting.
* \return 1 if 1-3 diagonal is better, 2 if 2-4
* diagonal is better, 0 if error occurs.