Learning synchronous context-free grammars with multiple specialised non-terminals for hierarchical phrase-based translation{}^{*}
Table 3: BLEU scores obtained by the Blue-Fringe clustering algorithm for different values of α. The performance of the baseline HSMT system is 0.5818.
['[ITALIC] α', '# final non-terminals', 'BLEU']
The amount of output non-terminals in the inferred context-free grammar is also reported. The best results are obtained with α=10−2. The performance of the baseline hierarchical phrase-based system [chiang2005] is 0.5818. The difference in performance is statistically significant for the figures in bold according to paired bootstrap resampling [koehn04:_statis] with p=0.05.