Refining the r-index

Hideo Bannai, Travis Gagie, Tomohiro I

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


Gagie, Navarro and Prezza's r-index (SODA, 2018) promises to speed up DNA alignment and variation calling by allowing us to index entire genomic databases, provided certain obstacles can be overcome. In this paper we first strengthen and simplify Policriti and Prezza's Toehold Lemma (DCC '16; Algorithmica, 2017), which inspired the r-index and plays an important role in its implementation. We then show how to update the r-index efficiently after adding a new genome to the database, which is likely to be vital in practice. As a by-product of this result, we obtain an online version of Policriti and Prezza's algorithm for constructing the LZ77 parse from a run-length compressed Burrows-Wheeler Transform. Our experiments demonstrate the practicality of all three of these results. Finally, we show how to augment the r-index such that, given a new genome and fast random access to the database, we can quickly compute the matching statistics and maximal exact matches of the new genome with respect to the database.

Original languageEnglish
Pages (from-to)96-108
Number of pages13
JournalTheoretical Computer Science
Publication statusPublished - Apr 6 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • General Computer Science


Dive into the research topics of 'Refining the r-index'. Together they form a unique fingerprint.

Cite this