Meta-Learning for Low-Resource Neural Machine Translation
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/D18-1398.pdf
Summary
Neural machine translation performs poorly when parallel data is scarce. Earlier remedies used monolingual corpora or multilingual and transfer learning. Gu et al. treat each language pair as a separate task and apply model-agnostic meta-learning (MAML). The goal is a parameter initialization that a new low-resource pair can adapt from in only a few updates. During meta-training, the system repeatedly samples one high-resource pair and runs a short simulated fine-tuning on one subset of its data. It then updates the shared starting point based on how well the adapted model does on a second subset. Languages do not share a vocabulary, so the authors add the universal lexical representation (ULR) to align inputs and outputs across languages. The resulting system, MetaNMT, learns from 18 European source languages and is tested on five target languages, all translating into English. It beat the multilingual transfer-learning baseline on every target pair, and its advantage widened as training data shrank. This makes usable NMT more realistic for languages with very small parallel corpora.
Key points
- Data: The source tasks are 17 Europarl languages plus Russian from WMT. The target tasks are Ro, Lv, Fi, Tr and Ko into English, with at most 160k tokens of training data per target.
- Headline result: MetaNMT reached 22.04 BLEU on Romanian-English WMT'16 after fine-tuning on only about 16,000 English tokens (roughly 600 sentence pairs).
- Comparison and training: MetaNMT outperformed the multilingual transfer approach of Zoph et al. (2016) on all five targets. That baseline saturated and then degraded during training, while MetaNMT kept improving.
- Effect of source tasks: Moving from one to 18 source tasks gave up to a 2× gain on Lv-En, Fi-En, Tr-En and Ko-En. Which source languages helped most depended on the target: Ro-En benefited more from {Es, Fr, It, Pt}, while the other targets benefited more from {De, Ru}.
- Method details: The meta-gradient can be simplified by dropping the second-order term. The choice of validation task for early stopping (e.g., Ro-En vs. Tr-En) noticeably affected final quality.
Cited by
- Massively Multilingual Neural Machine Translation in the Wild: Findings and Challenges
- The FLORES Evaluation Datasets for Low-Resource Machine Translation: Nepali–English and Sinhala–English
- Exploiting Cloze-Questions for Few-Shot Text Classification and Natural Language Inference
Cite
@inproceedings{gu2018meta,
title = {{Meta-Learning for Low-Resource Neural Machine Translation}},
author = {Gu, Jiatao and Wang, Yong and Chen, Yun and Cho, Kyunghyun and Li, Victor O.K.},
booktitle = {Proceedings of the 2018 Conference on Empirical Methods in Natural Language Processing},
year = {2018},
doi = {10.18653/v1/d18-1398},
url = {https://doi.org/10.18653/v1/d18-1398}
}References
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