Transformer Architecture Search for Improving Out-of-Domain Generalization in Machine Translation.

Interest in automatically searching for Transformer neural architectures for machine translation (MT) has been increasing. Current methods show promising results in in-domain settings, where training and test data share the same distribution. However, in real-world MT applications, it is common that the test data has a different distribution than the training data. In these out-of-domain (OOD) situations, Transformer architectures optimized for the linguistic characteristics of the training sentences struggle to produce accurate translations for OOD sentences during testing. To tackle this issue, we propose a multi-level optimization based method to automatically search for neural architectures that possess robust OOD generalization capabilities. During the architecture search process, our method automatically synthesizes approximated OOD MT data, which is used to evaluate and improve the architectures' ability of generalizing to OOD scenarios. The generation of approximated OOD data and the search for optimal architectures are executed in an integrated, end-to-end manner. Evaluated across multiple datasets, our method demonstrates strong OOD generalization performance, surpassing state-of-the-art approaches. Our code is publicly available at https://github.com/yihenghe/transformer_nas.