An attentional mechanism has lately been used to improve neural machine
translation (NMT) by selectively focusing on parts of the source sentence
during translation. However, there has been little work exploring useful
architectures for attention-based NMT. This paper examines two simple and
effective classes of attentional mechanism: a global approach which always
attends to all source words and a local one that only looks at a subset of
source words at a time. We demonstrate the effectiveness of both approaches
over the WMT translation tasks between English and German in both directions.
With local attention, we achieve a significant gain of 5.0 BLEU points over
non-attentional systems which already incorporate known techniques such as
dropout. Our ensemble model using different attention architectures has
established a new state-of-the-art result in the WMT'15 English to German
translation task with 25.9 BLEU points, an improvement of 1.0 BLEU points over
the existing best system backed by NMT and an n-gram reranker.

本文研究了两种简单而有效的注意力机制 —— 全局式和局部式，证明了这两种方法在英德翻译任务中的有效性，并使用不同的注意力架构建立了一个新的 WMT'15 英德翻译任务最佳结果的集成模型，其 BLEU 分数为 25.9 分，比现有的最佳基于 NMT 和 n-gram reranker 的系统提高 1.0 分。