arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2009.09372cs.CLcs.AI
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用于训练神经机器翻译模型的Softmax回火

Softmax Tempering for Training Neural Machine Translation Models

National Institute of Information and Communications Technology(国立信息通信技术研究所)

Raj Dabre, Atsushi Fujita

摘要:

神经机器翻译(NMT)模型通常使用softmax交叉熵损失进行训练,其中softmax分布与平滑的黄金标签进行比较。在低资源场景中,NMT模型往往会过度拟合,因为softmax分布很快接近黄金标签分布。为了解决这个问题,我们建议在训练期间应用softmax之前将logit除以温度系数。在我们对亚洲语言树库数据集和WMT 2019英语到德语翻译任务中的11种语言对进行的实验中,我们观察到翻译质量显著提高了3.9个BLEU点。此外,softmax回火使得贪婪搜索在翻译质量方面与束搜索解码一样好,能够实现1.5至3.5倍的加速。我们还研究了softmax回火对多语言NMT和递归堆叠NMT的影响,这两种方法的目的都是通过参数共享来减小NMT模型的大小,从而验证温度在开发紧凑型NMT模型中的实用性。最后,对softmax熵和梯度的分析揭示了我们的方法对NMT模型内部行为的影响。

英文摘要:

Neural machine translation (NMT) models are typically trained using a softmax cross-entropy loss where the softmax distribution is compared against smoothed gold labels. In low-resource scenarios, NMT models tend to over-fit because the softmax distribution quickly approaches the gold label distribution. To address this issue, we propose to divide the logits by a temperature coefficient, prior to applying softmax, during training. In our experiments on 11 language pairs in the Asian Language Treebank dataset and the WMT 2019 English-to-German translation task, we observed significant improvements in translation quality by up to 3.9 BLEU points. Furthermore, softmax tempering makes the greedy search to be as good as beam search decoding in terms of translation quality, enabling 1.5 to 3.5 times speed-up. We also study the impact of softmax tempering on multilingual NMT and recurrently stacked NMT, both of which aim to reduce the NMT model size by parameter sharing thereby verifying the utility of temperature in developing compact NMT models. Finally, an analysis of softmax entropies and gradients reveal the impact of our method on the internal behavior of NMT models.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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