BPE and CharCNNs for Translation of Morphology: A Cross-Lingual Comparison and Analysis
Table 2: BLEU scores comparing combinations of BPE and charCNN.
['[EMPTY]', 'word+tok', 'word+char', 'bpe+tok', 'bpe+char', 'stem+tok', 'stem+char']
The general improvements of bpe+char over word+char and bpe+tok indicate that character modeling and BPE sub-units are complementary. We also see that the charCNN is consistently part of the best solution for handling source morphology, while this is not always the case for BPE. In particular, for Semitic languages, bpe+char is only marginally better than word+char in Arabic and substantially worse in Hebrew.