Language-Informed Beam Search Decoding for Multilingual Machine Translation

Yilin Yang, Stefan Lee, Prasad Tadepalli


Abstract
Beam search decoding is the de-facto method for decoding auto-regressive Neural Machine Translation (NMT) models, including multilingual NMT where the target language is specified as an input. However, decoding multilingual NMT models commonly produces off-target translations – yielding translation outputs not in the intended language.In this paper, we first conduct an error analysis of off-target translations for a strong multilingual NMT model and identify how these decodings are produced during beam search. We then propose Language-informed Beam Search (LiBS), a general decoding algorithm incorporating an off-the-shelf Language Identification (LiD) model into beam search decoding to reduce off-target translations. LiBS is an inference-time procedure that is NMT-model agnostic and does not require any additional parallel data. Results show that our proposed LiBS algorithm on average improves +1.1 BLEU and +0.9 BLEU on WMT and OPUS datasets, and reduces off-target rates from 22.9% to 7.7% and 65.8% to 25.3% respectively.
Anthology ID:
2024.findings-acl.932
Volume:
Findings of the Association for Computational Linguistics ACL 2024
Month:
August
Year:
2024
Address:
Bangkok, Thailand and virtual meeting
Editors:
Lun-Wei Ku, Andre Martins, Vivek Srikumar
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
15761–15772
Language:
URL:
https://aclanthology.org/2024.findings-acl.932
DOI:
Bibkey:
Cite (ACL):
Yilin Yang, Stefan Lee, and Prasad Tadepalli. 2024. Language-Informed Beam Search Decoding for Multilingual Machine Translation. In Findings of the Association for Computational Linguistics ACL 2024, pages 15761–15772, Bangkok, Thailand and virtual meeting. Association for Computational Linguistics.
Cite (Informal):
Language-Informed Beam Search Decoding for Multilingual Machine Translation (Yang et al., Findings 2024)
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PDF:
https://aclanthology.org/2024.findings-acl.932.pdf