Mohamed Maher
2022
Language Tokens: A Frustratingly Simple Approach Improves Zero-Shot Performance of Multilingual Translation
Muhammad ElNokrashy
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Amr Hendy
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Mohamed Maher
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Mohamed Afify
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Hany Hassan Awadalla
Proceedings of the 15th biennial conference of the Association for Machine Translation in the Americas (Volume 1: Research Track)
This paper proposes a simple yet effective method to improve direct (X-to-Y) translation for both cases: zero-shot and when direct data is available. We modify the input tokens at both the encoder and decoder to include signals for the source and target languages. We show a performance gain when training from scratch, or finetuning a pretrained model with the pro- posed setup. In the experiments, our method shows nearly 10.0 BLEU points gain on in-house datasets depending on the checkpoint selection criteria. In a WMT evaluation campaign, From- English performance improves by 4.17 and 2.87 BLEU points, in the zero-shot setting, and when direct data is available for training, respectively. While X-to-Y improves by 1.29 BLEU over the zero-shot baseline, and 0.44 over the many-to-many baseline. In the low-resource setting, we see a 1.5 ∼ 1.7 point improvement when finetuning on X-to-Y domain data.