Unsupervised Cross-lingual Representation Learning at Scale
Paper · 2020 · Alexis Conneau, Kartikay Khandelwal, Naman Goyal et al.
Summary
The authors seek a way to improve cross-lingual text understanding when a single model serves many languages, including low-resource ones. Earlier multilingual models (mBERT, XLM) were trained on Wikipedia, which contains too little text for most languages. The Facebook AI team assembled CC-100, a cleaned corpus for 100 languages built from CommonCrawl and totaling about 2.5 TB. On it they trained XLM-R, a Transformer-based masked language model. It builds on the XLM approach, with modifications for large scale: a SentencePiece vocabulary of 250K tokens, no language embeddings, and longer training. The authors also study the trade-offs of scaling. When languages are added without increasing model size, low-resource languages benefit at first, but quality eventually declines for all languages. They call this phenomenon the curse of multilinguality and show that increasing model size mitigates it. XLM-R clearly outperforms mBERT on XNLI, MLQA and NER, and on GLUE it is nearly on par with the best monolingual models. The significance of the work is that it was the first to show that a single model covering a hundred languages can preserve the quality of each individual language. The authors released the code, data and models.
Key points
- Resources: the CC-100 corpus (100 languages, including Ukrainian) and two models: XLM-R Base (270M parameters) and XLM-R (550M, 24 layers). For low-resource languages, the amount of data increased by several orders of magnitude compared with Wikipedia.
- Compared with mBERT: on average +14.6% accuracy on XNLI, +13% F1 on MLQA and +2.4% F1 on NER (CoNLL-2002/2003). Compared with earlier XLM models, the gain on XNLI is +15.7% for Swahili and +11.4% for Urdu.
- Compared with the previous state of the art: +5.1% accuracy on XNLI, +2.42 F1 on NER and +9.1 F1 on MLQA.
- Multilingual model versus monolingual ones: on GLUE, XLM-R is on average only 1.0% behind RoBERTa and 1.6% ahead of BERT Large. In the translate-train-all setting, the multilingual XLM-7 trained on CC achieved 80.0% on XNLI, versus 77.5% for monolingual BERT models.
- Practical takeaway on data: training a BERT-like model typically requires at least a few hundred MiB of text in a language. Pretraining on Wikipedia for Swahili and Urdu yielded roughly the same result as a randomly initialized model.
Institutions
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 works
🧭 Topics 1Research subjects and languages the work is about.Multilingual & cross-lingual NLP · 882 works
Cite
Cite as Alexis Conneau, Kartikay Khandelwal, Naman Goyal, Vishrav Chaudhary, Guillaume Wenzek, Francisco Guzmán, Edouard Grave, Myle Ott, Luke Zettlemoyer and Veselin Stoyanov. 2020. Unsupervised Cross-lingual Representation Learning at Scale. Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics.
@inproceedings{conneau2020unsupervised,
title = {{Unsupervised Cross-lingual Representation Learning at Scale}},
author = {Alexis Conneau, Kartikay Khandelwal, Naman Goyal, Vishrav Chaudhary, Guillaume Wenzek, Francisco Guzmán, Edouard Grave, Myle Ott, Luke Zettlemoyer and Veselin Stoyanov},
booktitle = {Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics},
year = {2020},
doi = {10.18653/v1/2020.acl-main.747},
eprint = {1911.02116},
archivePrefix = {arXiv},
url = {https://doi.org/10.18653/v1/2020.acl-main.747}
}References
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