Is Neural Machine Translation Ready for Deployment? A Case Study on 30 Translation Directions
Summary
The paper asks whether neural machine translation can replace phrase-based statistical systems in a large, purely in-domain production setting such as the United Nations. The authors use the fully aligned six-language subcorpus of the United Nations Parallel Corpus v1.0, which covers Arabic, Chinese, English, French, Russian and Spanish. They train attentional encoder-decoder models with Nematus on BPE subwords and compare them, across all 30 translation directions, against a strong Moses configuration modelled on the UN's in-house systems. For the ten English-centred directions they also add a Hiero baseline. NMT equals or outperforms phrase-based SMT in every direction except French→Spanish. The largest gains are for pairs involving Chinese, and Arabic pairs also improve clearly. The second part presents AmuNMT, a C++ beam-search decoder for Nematus models, and examines speed trade-offs: checkpoint ensembling versus averaging, beam size and output-vocabulary selection. The authors find that one consumer GPU already delivers throughput competitive with the deployed Moses setup. This makes NMT a practical option for organizations with large in-house parallel data.
Key points
- Data: the 6-way UN subcorpus has 86,307 documents, about 11.4M lines and about 335M English tokens. Official dev and test sets of 4,000 sentences each come from 2015 documents. Text was lowercased and tokenized with Moses, Chinese was segmented with Jieba, and BPE used 30,000 units.
- For directions involving Chinese, NMT beats PB-SMT by roughly 7–9 BLEU. Hiero improves over PB-SMT for zh–en and en–zh but recovers less than half of the NMT gain.
- Doubling NMT training from 1.2M to 2.4M iterations (about 8 to 16 days on a GTX 1080) added 0.3–1.3 BLEU. No further benefit appeared beyond about 2M iterations.
- On en–fr, averaging the last 8 checkpoints (51.35 BLEU, 860 words/s) nearly matches a 4-checkpoint ensemble (51.38 BLEU, 200 words/s). A beam of 5 scores only 0.2 BLEU below the best beam size.
- AmuNMT's vocabulary selection (K = 75, K′ = 75, about 1,250 items per sentence) leaves BLEU unchanged. A single GPU outperforms 16 threads on server-grade Xeon CPUs.
Cited by
- Taking MT Evaluation Metrics to Extremes: Beyond Correlation with Human Judgments
- A Challenge Set Approach to Evaluating Machine Translation
- Investigating Backtranslation in Neural Machine Translation
Cite
@inproceedings{junczysdowmunt2016is,
title = {{Is Neural Machine Translation Ready for Deployment? A Case Study on 30 Translation Directions}},
author = {Junczys-Dowmunt, Marcin and Dwojak, Tomasz and Hoang, Hieu},
booktitle = {Proceedings of the 13th International Conference on Spoken Language Translation},
year = {2016},
url = {https://aclanthology.org/2016.iwslt-1.5/}
}References
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