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Indexing highly repetitive texts --- such as genomic databases, software repositories and versioned text collections --- has become an important problem since the turn of the millennium. A relevant compressibility measure for repetitive…

Data Structures and Algorithms · Computer Science 2017-07-13 Travis Gagie , Gonzalo Navarro , Nicola Prezza

We show how to build several data structures of central importance to string processing, taking as input the Burrows-Wheeler transform (BWT) and using small extra working space. Let $n$ be the text length and $\sigma$ be the alphabet size.…

Data Structures and Algorithms · Computer Science 2019-08-14 Nicola Prezza , Giovanna Rosone

Until recently, most experts would probably have agreed we cannot backwards-step in constant time with a run-length compressed Burrows-Wheeler Transform (RLBWT), since doing so relies on rank queries on sparse bitvectors and those inherit…

Data Structures and Algorithms · Computer Science 2022-07-15 Nathaniel K. Brown , Travis Gagie , Massimiliano Rossi

Indexing very large collections of strings, such as those produced by the widespread next generation sequencing technologies, heavily relies on multistring generalization of the Burrows-Wheeler Transform (BWT): large requirements of…

Data Structures and Algorithms · Computer Science 2020-12-07 Paola Bonizzoni , Gianluca Della Vedova , Yuri Pirola , Marco Previtali , Raffaella Rizzi

Advances in DNA sequencing technology have stimulated the development of algorithms and tools for processing very large collections of short strings (reads). Short-read alignment and assembly are among the most well-studied problems. Many…

Genomics · Quantitative Biology 2014-01-30 Chi-Man Liu , Ruibang Luo , Tak-Wah Lam

The move structure represents permutations with long contiguously permuted intervals in compressed space with optimal query time. They have become an important feature of compressed text indexes using space proportional to the number of…

Data Structures and Algorithms · Computer Science 2026-04-28 Nathaniel K. Brown , Ben Langmead

We prove that for every integer $n > 0$ and for every alphabet $\Sigma_k$ of size $k \geq 3$, there exists a necklace of length $n$ whose Burrows-Wheeler Transform (BWT) is completely unclustered, i.e., it consists of exactly $n$ runs with…

Discrete Mathematics · Computer Science 2025-08-29 Gabriele Fici , Estéban Gabory , Giuseppe Romana , Marinella Sciortino

The run-length compressed Burrows-Wheeler transform (RLBWT) used in conjunction with the backward search introduced in the FM index is the centerpiece of most compressed indexes working on highly-repetitive data sets like biological…

Data Structures and Algorithms · Computer Science 2021-10-05 Jin Jie Deng , Wing-Kai Hon , Dominik Köppl , Kunihiko Sadakane

Detecting all the strings that occur in a text more frequently or less frequently than expected according to an IID or a Markov model is a basic problem in string mining, yet current algorithms are based on data structures that are either…

Data Structures and Algorithms · Computer Science 2015-08-13 Djamal Belazzougui , Fabio Cunial

The Burrows-Wheeler Transform (BWT) moves characters with similar contexts in a text together, where a character's context consists of the characters immediately following it. We say that a property has contextual locality if characters…

Data Structures and Algorithms · Computer Science 2024-11-26 Travis Gagie

The field of succinct data structures has flourished over the last 16 years. Starting from the compressed suffix array (CSA) by Grossi and Vitter (STOC 2000) and the FM-index by Ferragina and Manzini (FOCS 2000), a number of generalizations…

Data Structures and Algorithms · Computer Science 2016-09-22 Djamal Belazzougui , Fabio Cunial , Juha Kärkkäinen , Veli Mäkinen

In this paper we study the number $r_{bwt}$ of equal-letter runs produced by the Burrows-Wheeler transform ($BWT$) when it is applied to purely morphic finite words, which are words generated by iterating prolongable morphisms. Such a…

Formal Languages and Automata Theory · Computer Science 2022-02-08 Andrea Frosini , Ilaria Mancini , Simone Rinaldi , Giuseppe Romana , Marinella Sciortino

We first review how we can store a run-length compressed suffix array (RLCSA) for a text $T$ of length $n$ over an alphabet of size $\sigma$ whose Burrows-Wheeler Transform (BWT) consists of $r$ runs in $O \left( \rule{0ex}{2ex} r \log (n /…

Data Structures and Algorithms · Computer Science 2025-04-22 Nathaniel K. Brown , Travis Gagie , Giovanni Manzini , Gonzalo Navarro , Marinella Sciortino

We show how to merge two run-length compressed Burrows-Wheeler Transforms (RLBWTs) into a run-length compressed extended Burrows-Wheeler Transform (eBWT) in $O (r)$ space and $O ((r + L) \log (m + n))$ time, where $m$ and $n$ are the…

Data Structures and Algorithms · Computer Science 2026-04-16 Travis Gagie

Mantaci et al. [TCS 2007] defined the eBWT to extend the definition of the BWT to a collection of strings, however, since this introduction, it has been used more generally to describe any BWT of a collection of strings and the fundamental…

Data Structures and Algorithms · Computer Science 2021-06-22 Christina Boucher , Davide Cenzato , Zsuzsanna Lipták , Massimiliano Rossi , Marinella Sciortino

Indexing highly repetitive texts - such as genomic databases, software repositories and versioned text collections - has become an important problem since the turn of the millennium. A relevant compressibility measure for repetitive texts…

Data Structures and Algorithms · Computer Science 2020-12-17 Travis Gagie , Gonzalo Navarro , Nicola Prezza

With the rapid growing of data and number of applications, there is a crucial need of dictionary based reversible transformation techniques to increase the efficiency of the compression algorithms and hence contribute towards the…

Information Theory · Computer Science 2014-03-20 R. R. Baruah , V. Deka , M. P. Bhuyan

In this paper we show how to use one or more assembled or partially assembled genome as the basis for a compressed full-text index of its readset. Specifically, we build a labelled tree by taking the assembled genome as a trunk and grafting…

Data Structures and Algorithms · Computer Science 2021-06-02 Travis Gagie , Garance Gourdel , Giovanni Manzini

We survey the different methods used for extending the BWT to collections of strings, following largely [Cenzato and Lipt\'ak, CPM 2022, Bioinformatics 2024]. We analyze the specific aspects and combinatorial properties of the resulting BWT…

Data Structures and Algorithms · Computer Science 2025-06-03 Davide Cenzato , Zsuzsanna Lipták , Nadia Pisanti , Giovanna Rosone , Marinella Sciortino

Bitmap indexes must be compressed to reduce input/output costs and minimize CPU usage. To accelerate logical operations (AND, OR, XOR) over bitmaps, we use techniques based on run-length encoding (RLE), such as Word-Aligned Hybrid (WAH)…

Databases · Computer Science 2016-08-02 Daniel Lemire , Owen Kaser , Kamel Aouiche