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The \emph{longest common extension} (\emph{LCE}) problem is to preprocess a given string $w$ of length $n$ so that the length of the longest common prefix between suffixes of $w$ that start at any two given positions is answered quickly. In…

Data Structures and Algorithms · Computer Science 2017-02-27 Yuka Tanimura , Takaaki Nishimoto , Hideo Bannai , Shunsuke Inenaga , Masayuki Takeda

The Burrows-Wheeler Transform (BWT) is an important technique both in data compression and in the design of compact indexing data structures. It has been generalized from single strings to collections of strings and some classes of labeled…

Data Structures and Algorithms · Computer Science 2019-05-30 Jarno Alanko , Travis Gagie , Gonzalo Navarro , Louisa Seelbach Benkner

We introduce the first self-index based on the Lempel-Ziv 1977 compression format (LZ77). It is particularly competitive for highly repetitive text collections such as sequence databases of genomes of related species, software repositories,…

Data Structures and Algorithms · Computer Science 2011-01-24 Sebastian Kreft , Gonzalo Navarro

The k-spectrum of a string is the set of all distinct substrings of length k occurring in the string. K-spectra have many applications in bioinformatics including pseudoalignment and genome assembly. The Spectral Burrows-Wheeler Transform…

Data Structures and Algorithms · Computer Science 2023-06-09 Jarno N. Alanko , Elena Biagi , Simon J. Puglisi

It was recently proved that any SLP generating a given string $w$ can be transformed in linear time into an equivalent balanced SLP of the same asymptotic size. We show that this result also holds for RLSLPs, which are SLPs extended with…

Data Structures and Algorithms · Computer Science 2022-06-28 Gonzalo Navarro , Francisco Olivares , Cristian Urbina

The positional Burrows-Wheeler Transform (PBWT) is commonly used to store haplotype panels compactly in such a way that, given a query haplotype, we can quickly find the set maximal exact matches (SMEMs) between the query and the haplotypes…

Data Structures and Algorithms · Computer Science 2026-05-26 Travis Gagie

In this paper, we study whether an off-the-shelf LLM can be adapted into a discrete, variable-length token compressor and decompressor for long-context processing. To this end, we design a self-expressive autoencoding framework that…

Computation and Language · Computer Science 2026-05-14 Wenbing Li , Yiran Wang , Zikai Song , Jielei Zhang , Tianhao Zhao , Junkai Lin , Wei Yang

Tokenization efficiency plays a critical role in the performance and cost of large language models (LLMs), yet most models rely on static tokenizers optimized on general-purpose corpora. These tokenizers' fixed vocabularies often fail to…

Computation and Language · Computer Science 2025-10-27 Saibo Geng , Nathan Ranchin , Yunzhen yao , Maxime Peyrard , Chris Wendler , Michael Gastpar , Robert West

The Burrows Wheeler transform has applications in data compression as well as full text indexing. Despite its important applications and various existing algorithmic approaches the construction of the transform for large data sets is still…

Data Structures and Algorithms · Computer Science 2016-04-25 German Tischler

The aim of this note is to provide some reference facts for LZW---mostly from Thomas and Cover \cite{Cover:2006aa} and provide a reference for some metrics that can be derived from it. LZW is an algorithm to compute a Kolmogorov Complexity…

Information Theory · Computer Science 2017-08-01 Giulio Ruffini

A well-known fact in the field of lossless text compression is that high-order entropy is a weak model when the input contains long repetitions. Motivated by this, decades of research have generated myriads of so-called dictionary…

Data Structures and Algorithms · Computer Science 2020-12-17 Dominik Kempa , Nicola Prezza

Transformer-based Large Language Models (LLMs) often impose limitations on the length of the text input to ensure the generation of fluent and relevant responses. This constraint restricts their applicability in scenarios involving long…

Computation and Language · Computer Science 2023-12-18 Weizhi Fei , Xueyan Niu , Pingyi Zhou , Lu Hou , Bo Bai , Lei Deng , Wei Han

Large Language Models (LLMs) excel at rewriting tasks such as text style transfer and grammatical error correction. While there is considerable overlap between the inputs and outputs in these tasks, the decoding cost still increases with…

Computation and Language · Computer Science 2025-01-24 Hao Zhang , Felix Stahlberg , Shankar Kumar

Popular sequence alignment tools such as BWA convert a reference genome to an indexing data structure based on the Burrows-Wheeler Transform (BWT), from which matches to individual query sequences can be rapidly determined. However the…

Genomics · Quantitative Biology 2013-04-23 Anthony J. Cox , Tobias Jakobi , Giovanna Rosone , Ole B. Schulz-Trieglaff

Language models usually use left-to-right (L2R) autoregressive factorization. However, L2R factorization may not always be the best inductive bias. Therefore, we investigate whether alternative factorizations of the text distribution could…

Computation and Language · Computer Science 2025-07-01 Yizhe Zhang , Richard Bai , Zijin Gu , Ruixiang Zhang , Jiatao Gu , Emmanuel Abbe , Samy Bengio , Navdeep Jaitly

Large Language Models (LLMs) have recently achieved remarkable progress by leveraging Reinforcement Learning and extended Chain-of-Thought (CoT) techniques. However, the challenge of performing efficient language reasoning--especially…

Computation and Language · Computer Science 2025-06-17 Zhong-Zhi Li , Xiao Liang , Zihao Tang , Lei Ji , Peijie Wang , Haotian Xu , Xing W , Haizhen Huang , Weiwei Deng , Yeyun Gong , Zhijiang Guo , Xiao Liu , Fei Yin , Cheng-Lin Liu

Indexing highly repetitive collections has become a relevant problem with the emergence of large repositories of versioned documents, among other applications. These collections may reach huge sizes, but are formed mostly of documents that…

Information Retrieval · Computer Science 2016-05-25 Francisco Claude , Antonio Fariña , Miguel A. Martínez-Prieto , Gonzalo Navarro

Existing work on prompt compression for Large Language Models (LLM) focuses on lossy methods that try to maximize the retention of semantic information that is relevant to downstream tasks while significantly reducing the sequence length.…

Computation and Language · Computer Science 2025-08-22 John Harvill , Ziwei Fan , Hao Wang , Luke Huan , Anoop Deoras , Yizhou Sun , Hao Ding

The paper introduces a new lossless, highly robust compression algorithm that similar with LZW algorithm, yet the algorithm discards dictionary processing and uses irregular sequences with massive, random information instead. Then the paper…

Signal Processing · Electrical Eng. & Systems 2020-06-24 Rui Zhu

We describe a grammar for DNA sequencing reads from which we can compute the BWT directly. Our motivation is to perform in succinct space genomic analyses that require complex string queries not yet supported by repetition-based…

Data Structures and Algorithms · Computer Science 2020-11-17 Diego Díaz-Domínguez , Gonzalo Navarro