Algorithms for Weighted Pushdown Automata
Alexandra
Butoi
author
Brian
DuSell
author
Tim
Vieira
author
Ryan
Cotterell
author
David
Chiang
author
2022-12
text
Proceedings of the 2022 Conference on Empirical Methods in Natural Language Processing
Association for Computational Linguistics
Abu Dhabi, United Arab Emirates
conference publication
Weighted pushdown automata (WPDAs) are at the core of many natural language processing tasks, like syntax-based statistical machine translation and transition-based dependency parsing. As most existing dynamic programming algorithms are designed for context-free grammars (CFGs), algorithms for PDAs often resort to a PDA-to-CFG conversion. In this paper, we develop novel algorithms that operate directly on WPDAs. Our algorithms are inspired by Lang’s algorithm, but use a more general definition of pushdown automaton and either reduce the space requirements by a factor of |Gamma| (the size of the stack alphabet) or reduce the runtime by a factor of more than |Q| (the number of states). When run on the same class of PDAs as Lang’s algorithm, our algorithm is both more space-efficient by a factor of |Gamma| and more time-efficient by a factor of |Q| x |Gamma|.
butoi-etal-2022-algorithms
10.18653/v1/2022.emnlp-main.656
https://aclanthology.org/2022.emnlp-main.656
2022-12
9669
9680