Improving Language Model Integration for Neural Machine Translation

Christian Herold, Yingbo Gao, Mohammad Zeineldeen, Hermann Ney


Abstract
The integration of language models for neural machine translation has been extensively studied in the past. It has been shown that an external language model, trained on additional target-side monolingual data, can help improve translation quality. However, there has always been the assumption that the translation model also learns an implicit target-side language model during training, which interferes with the external language model at decoding time. Recently, some works on automatic speech recognition have demonstrated that, if the implicit language model is neutralized in decoding, further improvements can be gained when integrating an external language model. In this work, we transfer this concept to the task of machine translation and compare with the most prominent way of including additional monolingual data - namely back-translation. We find that accounting for the implicit language model significantly boosts the performance of language model fusion, although this approach is still outperformed by back-translation.
Anthology ID:
2023.findings-acl.444
Volume:
Findings of the Association for Computational Linguistics: ACL 2023
Month:
July
Year:
2023
Address:
Toronto, Canada
Editors:
Anna Rogers, Jordan Boyd-Graber, Naoaki Okazaki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
7114–7123
Language:
URL:
https://aclanthology.org/2023.findings-acl.444
DOI:
10.18653/v1/2023.findings-acl.444
Bibkey:
Cite (ACL):
Christian Herold, Yingbo Gao, Mohammad Zeineldeen, and Hermann Ney. 2023. Improving Language Model Integration for Neural Machine Translation. In Findings of the Association for Computational Linguistics: ACL 2023, pages 7114–7123, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
Improving Language Model Integration for Neural Machine Translation (Herold et al., Findings 2023)
Copy Citation:
PDF:
https://aclanthology.org/2023.findings-acl.444.pdf