Fast and scalable decoding with language model look-ahead for phrase-based statistical machine translation

  • Authors:
  • Joern Wuebker;Hermann Ney;Richard Zens

  • Affiliations:
  • RWTH Aachen University, Germany;RWTH Aachen University, Germany;Google, Inc., Mountain View, CA

  • Venue:
  • ACL '12 Proceedings of the 50th Annual Meeting of the Association for Computational Linguistics: Short Papers - Volume 2
  • Year:
  • 2012

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Abstract

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 efficiency 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.