Non-Parametric Unsupervised Domain Adaptation for Neural Machine Translation

Xin Zheng, Zhirui Zhang, Shujian Huang, Boxing Chen, Jun Xie, Weihua Luo, Jiajun Chen


Abstract
Recently, kNN-MT (Khandelwal et al., 2020) has shown the promising capability of directly incorporating the pre-trained neural machine translation (NMT) model with domain-specific token-level k-nearest-neighbor (kNN) retrieval to achieve domain adaptation without retraining. Despite being conceptually attractive, it heavily relies on high-quality in-domain parallel corpora, limiting its capability on unsupervised domain adaptation, where in-domain parallel corpora are scarce or nonexistent. In this paper, we propose a novel framework that directly uses in-domain monolingual sentences in the target language to construct an effective datastore for k-nearest-neighbor retrieval. To this end, we first introduce an autoencoder task based on the target language, and then insert lightweight adapters into the original NMT model to map the token-level representation of this task to the ideal representation of the translation task. Experiments on multi-domain datasets demonstrate that our proposed approach significantly improves the translation accuracy with target-side monolingual data, while achieving comparable performance with back-translation. Our implementation is open-sourced at https://github.com/zhengxxn/UDA-KNN.
Anthology ID:
2021.findings-emnlp.358
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2021
Month:
November
Year:
2021
Address:
Punta Cana, Dominican Republic
Editors:
Marie-Francine Moens, Xuanjing Huang, Lucia Specia, Scott Wen-tau Yih
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
4234–4241
Language:
URL:
https://aclanthology.org/2021.findings-emnlp.358
DOI:
10.18653/v1/2021.findings-emnlp.358
Bibkey:
Cite (ACL):
Xin Zheng, Zhirui Zhang, Shujian Huang, Boxing Chen, Jun Xie, Weihua Luo, and Jiajun Chen. 2021. Non-Parametric Unsupervised Domain Adaptation for Neural Machine Translation. In Findings of the Association for Computational Linguistics: EMNLP 2021, pages 4234–4241, Punta Cana, Dominican Republic. Association for Computational Linguistics.
Cite (Informal):
Non-Parametric Unsupervised Domain Adaptation for Neural Machine Translation (Zheng et al., Findings 2021)
Copy Citation:
PDF:
https://aclanthology.org/2021.findings-emnlp.358.pdf
Video:
 https://aclanthology.org/2021.findings-emnlp.358.mp4
Code
 zhengxxn/uda-knn