  In this paper, we introduce a hybrid search for attention-based neural
machine translation (NMT). A target phrase learned with statistical MT models
extends a hypothesis in the NMT beam search when the attention of the NMT model
focuses on the source words translated by this phrase. Phrases added in this
way are scored with the NMT model, but also with SMT features including
phrase-level translation probabilities and a target language model.
Experimental results on German->English news domain and English->Russian
e-commerce domain translation tasks show that using phrase-based models in NMT
search improves MT quality by up to 2.3% BLEU absolute as compared to a strong
NMT baseline.
