Mitigating Data Imbalance and Representation Degeneration in Multilingual Machine Translation

Wen Lai, Alexandra Chronopoulou, Alexander Fraser


Abstract
Despite advances in multilingual neural machine translation (MNMT), we argue that there are still two major challenges in this area: data imbalance and representation degeneration. The data imbalance problem refers to the imbalance in the amount of parallel corpora for all language pairs, especially for long-tail languages (i.e., very low-resource languages). The representation degeneration problem refers to the problem of encoded tokens tending to appear only in a small subspace of the full space available to the MNMT model. To solve these two issues, we propose Bi-ACL, a framework which only requires target-side monolingual data and a bilingual dictionary to improve the performance of the MNMT model. We define two modules, named bidirectional autoencoder and bidirectional contrastive learning, which we combine with an online constrained beam search and a curriculum learning sampling strategy. Extensive experiments show that our proposed method is more effective than strong baselines both in long-tail languages and in high-resource languages. We also demonstrate that our approach is capable of transferring knowledge between domains and languages in zero-shot scenarios.
Anthology ID:
2023.findings-emnlp.953
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2023
Month:
December
Year:
2023
Address:
Singapore
Editors:
Houda Bouamor, Juan Pino, Kalika Bali
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
14279–14294
Language:
URL:
https://aclanthology.org/2023.findings-emnlp.953
DOI:
10.18653/v1/2023.findings-emnlp.953
Bibkey:
Cite (ACL):
Wen Lai, Alexandra Chronopoulou, and Alexander Fraser. 2023. Mitigating Data Imbalance and Representation Degeneration in Multilingual Machine Translation. In Findings of the Association for Computational Linguistics: EMNLP 2023, pages 14279–14294, Singapore. Association for Computational Linguistics.
Cite (Informal):
Mitigating Data Imbalance and Representation Degeneration in Multilingual Machine Translation (Lai et al., Findings 2023)
Copy Citation:
PDF:
https://aclanthology.org/2023.findings-emnlp.953.pdf