Baidu Neural Machine Translation Systems for WMT19

In this paper we introduce the systems Baidu submitted for the WMT19 shared task on Chinese <-> English news translation. Our systems are based on the Transformer architecture with some effective improvements. Data selection, back translation, data augmentation, knowledge distillation, domain adaptation, model ensemble and re-ranking are employed and proven effective in our experiments. Our Chinese -> English system achieved the highest case-sensitive BLEU score among all constrained submissions, and our English -> Chinese system ranked the second in all submissions.