A scalable decoder for parsing-based machine translation with equivalent language model state maintenance

  • Authors:
  • Zhifei Li;Sanjeev Khudanpur

  • Affiliations:
  • Johns Hopkins University, Baltimore, MD;Johns Hopkins University, Baltimore, MD

  • Venue:
  • SSST '08 Proceedings of the Second Workshop on Syntax and Structure in Statistical Translation
  • Year:
  • 2008

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Abstract

We describe a scalable decoder for parsing-based machine translation. The decoder is written in JAVA and implements all the essential algorithms described in Chiang (2007): chart-parsing, m-gram language model integration, beam- and cube-pruning, and unique k-best extraction. Additionally, parallel and distributed computing techniques are exploited to make it scalable. We also propose an algorithm to maintain equivalent language model states that exploits the back-off property of m-gram language models: instead of maintaining a separate state for each distinguished sequence of "state" words, we merge multiple states that can be made equivalent for language model probability calculations due to back-off. We demonstrate experimentally that our decoder is more than 30 times faster than a baseline decoder written in PYTHON. We propose to release our decoder as an open-source toolkit.