Fast and Scalable Decoding with Language Model Look-Ahead for Phrase-based Statistical Machine Translation

Joern Wuebker
Hermann Ney
Proceedings of the 50th Annual Meeting of the Association for Computational Linguistics, Association for Computational Linguistics, Jeju, Republic of Korea(2012), pp. 28-32


In this work we present two extensions to the well-known dynamic programming beam search in phrase-based statistical machine translation (SMT), aiming at increased effi- ciency of decoding by minimizing the number of language model computations and hypothesis expansions. Our results show that language model based pre-sorting yields a small improvement in translation quality and a speedup by a factor of 2. Two look-ahead methods are shown to further increase translation speed by a factor of 2 without changing the search space and a factor of 4 with the side-effect of some additional search errors. We compare our approach with Moses and observe the same performance, but a substantially better trade-off between translation quality and speed. At a speed of roughly 70 words per second, Moses reaches 17.2% BLEU, whereas our approach yields 20.0% with identical models.

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