On the scalability of data augmentation techniques for low-resource machine translation between Chinese and Vietnamese

ABSTRACT Neural Machine Translation (NMT) has constantly been shown to be a standard choice to build a translation system, in both academia and industry. For low-resource language pairs, data augmentation techniques have been widely used to tackle the data shortage problem in NMT. In this paper, we investigate the scaling behaviour of transformer-based NMT model to the increasing amount of synthetic data. Through the experiments, conducted in the Chinese-to-Vietnamese translation task, we aim to provide a guideline to the application of several methods such as back-translation, tagged back-translation, self-training and sentence concatenation in a low-resource, less-related language pair. Our results suggest that choosing the appropriate amount of synthetic data is a crucial task when building NMT systems. In addition, when combining methods, it is recommended to tag the data sources before training.