Graph Convolutional Encodersfor Syntax-aware Neural Machine Translation
Table 5: Validation BLEU for English-German and English-Czech for 1- and 2-layer GCNs.
['[EMPTY]', 'En-De BLEU1', 'En-De BLEU4', 'En-Cs BLEU1', 'En-Cs BLEU4']
S4SS2SSS1Px3 Effect of GCN layers. How many GCN layers do we need? Every layer gives us an extra hop in the graph and expands the syntactic neighborhood of a word. For English-German, using a 1-layer GCN improves BLEU-1, but surprisingly has little effect on BLEU4. Adding an additional layer gives improvements on both BLEU1 and BLEU4 of +1.3 and +0.73, respectively. For English-Czech, performance increases with each added GCN layer.