Generative Neural Machine Translation
Table 6: Test set BLEU scores for unseen pair translation. We use the VNMT and GNMT parameters trained with 4M paired sentences. For GNMT-Multi and GNMT-Multi-SSL, we train new models with 4M paired sentences, but with the respective language pairs excluded during training.
['System', '(EN, ES) unseen EN → ES', '(EN, ES) unseen ES → EN', '(EN, FR) unseen EN → FR', '(EN, FR) unseen FR → EN', '(ES, FR) unseen ES → FR', '(ES, FR) unseen FR → ES']
In this context, VNMT and GNMT perform similarly in terms of BLEU scores. However, both models are consistently outperformed by GNMT-Multi (albeit only by a small amount). Using monolingual data is very effective in this context, with GNMT-Multi-SSL outperforming all other models.