A CYK+ variant for SCFG decoding without a dot chart

Abstract

While CYK+ and Earley-style variants are popular algorithms for decoding unbinarized SCFGs, in particular for syntax-based Statistical Machine Translation, the algorithms rely on a so-called dot chart which suffers from a high memory consumption. We propose a recursive variant of the CYK+ algorithm that eliminates the dot chart, without incurring an increase in time complexity for SCFG decoding. In an evaluation on a string-to-tree SMT scenario, we empirically demonstrate substantial improvements in memory consumption and translation speed.