Synchronous Bidirectional Neural Machine Translation
Table 5: Results of WMT18 Russian-English translation using case-insensitive tokenized BLEU.
['Model', 'DEV', 'TEST']
Note that the BLEU score gains of English-German and Russian-English are not as significant as that on Chinese-English. The underlying reasons, which have also been mentioned in \newciteShen:2016 and \newcitezhang2018asynchronous, are that (1) the Chinese-English datasets contain four reference translations for each source sentence while the English-German and Russian-English datasets only have single reference; (2) English is more distantly related to Chinese than German and Russian, leading to the predominant improvements for Chinese-English translation when leveraging bidirectional decoding.