The encoder-decoder framework for neural machine translation (NMT) has been shown effective in large data scenarios, but is much less effective for low-resource languages. We present a transfer learning method that significantly improves Bleu scores across a range of low-resource languages. Our key idea is to first train a high-resource language pair (the parent model), then transfer some of the learned parameters to the low-resource pair (the child model) to initialize and constrain training. Using our transfer learning method we improve baseline NMT models by an average of 5.6 Bleu on four low-resource language pairs. Ensembling and unknown word replacement add another 2 Bleu which brings the NMT performance on low-resource machine translation close to a strong syntax based machine translation (SBMT) system, exceeding its performance on one language pair. Additionally, using the transfer learning model for re-scoring, we can improve the SBMT system by an average of 1.3 Bleu, improving the state-of-the-art on low-resource machine translation.

该研究提出了一种转移学习的方法，通过先训练一个高资源语言对以及将一些已学习的参数转移至低资源语言对，来初始化和约束训练，显著提高了Bleu分数，并将低资源机器翻译性能接近于强的基于语法的机器翻译系统，超过了其一个语言对的性能，并且用于重新评分可以进一步提高低资源机器翻译的表现。

面向低资源神经机器翻译的迁移学习