As a comparison, the system only using the position embedding (Row 4) improves the baseline with 0.37 BLEU.
we find an interesting result that when using pre-ordering and position embedding separately, the respective improvement is quite small (0.32 BLEU and 0.37 BLEU, respectively), but using them together can significantly boost the performance (1.13 BLEU), suggesting that pre-ordering and position embedding can enhance each other.