On the Approximation Ratio of Lempel-Ziv Parsing

@inproceedings{Gagie2018OnTA,
  title={On the Approximation Ratio of Lempel-Ziv Parsing},
  author={Travis Gagie and Gonzalo Navarro and Nicola Prezza},
  booktitle={LATIN},
  year={2018}
}
Shannon’s entropy is a clear lower bound for statistical compression. The situation is not so well understood for dictionary-based compression. A plausible lower bound is b, the least number of phrases of a general bidirectional parse of a text, where phrases can be copied from anywhere else in the text. Since computing b is NP-complete, a popular gold standard is z, the number of phrases in the Lempel-Ziv parse of the text, where phrases can be copied only from the left. While z can be… CONTINUE READING