Similarity-based Curriculum Learning for Multilingual Neural Machine Translation

Multilingual neural machine translation (MNMT) with a single model has drawn more attention due to its capability to deal with multiple languages.However,the current multilingual translation paradigm does not make use of the similar features embodied in different languages,which has already been proven useful for improving the multilingual translation.Besides,the training of multilingual model is usually very time-consuming due to the huge amount of training data.To address these problems,we propose a similarity-based curriculum learning method to improve the overall performance and convergence speed.We propose two hierarchical criteria for measuring the similarity,one is for ranking different languages (inter-language) with singular vector canonical correlation analysis,and the other is for ranking different sentences in a particular language (intra-language) with cosine similarity.At the same time,the paper proposes a curriculum learning strategy that takes the loss of validation set as the curriculum replacement standard.We conduct experiments on balanced and unbalanced IWSLT multilingual data sets and Europarl corpus datasets.The results demonstrate that the proposed method outperforms strong multilingual translation systems and can achieve up to a 64% decrease in training time.