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Order-preserving pattern matching was introduced recently but it has already attracted much attention. Given a reference sequence and a pattern, we want to locate all substrings of the reference sequence whose elements have the same…

Data Structures and Algorithms · Computer Science 2018-12-11 Gianni Decaroli , Travis Gagie , Giovanni Manzini

Implicit Neural Representations (INRs) are increasingly recognized as a versatile data modality for representing discretized signals, offering benefits such as infinite query resolution and reduced storage requirements. Existing signal…

Machine Learning · Computer Science 2025-03-26 Dhananjaya Jayasundara , Sudarshan Rajagopalan , Yasiru Ranasinghe , Trac D. Tran , Vishal M. Patel

In this paper, we show that the LZ77 factorization of a text T {\in\Sigma^n} can be computed in O(R log n) bits of working space and O(n log R) time, R being the number of runs in the Burrows-Wheeler transform of T reversed. For extremely…

Data Structures and Algorithms · Computer Science 2015-10-22 Nicola Prezza , Alberto Policriti

To store and search genomic databases efficiently, researchers have recently started building compressed self-indexes based on grammars. In this paper we show how, given a straight-line program with $r$ rules for a string (S [1..n]) whose…

Data Structures and Algorithms · Computer Science 2012-09-28 Travis Gagie , Paweł Gawrychowski , Juha Kärkkäinen , Yakov Nekrich , Simon J. Puglisi

We study the fundamental question of how efficiently suffix array entries can be accessed when the array cannot be stored explicitly. The suffix array $SA_T[1..n]$ of a text $T$ of length $n$ encodes the lexicographic order of its suffixes…

Data Structures and Algorithms · Computer Science 2025-10-23 Dominik Kempa , Tomasz Kociumaka

Text retrieval using learned sparse representations of queries and documents has, over the years, evolved into a highly effective approach to search. It is thanks to recent advances in approximate nearest neighbor search-with the emergence…

Information Retrieval · Computer Science 2026-02-06 Sebastian Bruch , Martino Fontana , Franco Maria Nardini , Cosimo Rulli , Rossano Venturini

We engineer a self-index based retrieval system capable of rank-safe evaluation of top-k queries. The framework generalizes the GREEDY approach of Culpepper et al. (ESA 2010) to handle multi-term queries, including over phrases. We propose…

Data Structures and Algorithms · Computer Science 2014-06-13 Simon Gog , Matthias Petri

Sparse suffix sorting is the problem of sorting $b=o(n)$ suffixes of a string of length $n$. Efficient sparse suffix sorting algorithms have existed for more than a decade. Despite the multitude of works and their justified claims for…

Data Structures and Algorithms · Computer Science 2024-07-08 Lorraine A. K. Ayad , Grigorios Loukides , Solon P. Pissis , Hilde Verbeek

A compressed full-text self-index represents a text in a compressed form and still answers queries efficiently. This technology represents a breakthrough over the text indexing techniques of the previous decade, whose indexes required…

Data Structures and Algorithms · Computer Science 2007-12-21 Paolo Ferragina , Rodrigo Gonzalez , Gonzalo Navarro , Rossano Venturini

Grammar-based compression is a popular and powerful approach to compressing repetitive texts but until recently its relatively poor time-space trade-offs during real-life construction made it impractical for truly massive datasets such as…

Data Structures and Algorithms · Computer Science 2020-07-21 Travis Gagie , Tomohiro I , Giovanni Manzini , Gonzalo Navarro , Hiroshi Sakamoto , Louisa Seelbach Benkner , Yoshimasa Takabatake

In this paper, we present the following results: (1) We propose a new \emph{dynamic compressed index} of $O(w)$ space, that supports searching for a pattern $P$ in the current text in $O(|P| f(M,w) + \log w \log |P| \log^* M (\log N + \log…

Data Structures and Algorithms · Computer Science 2016-04-07 Takaaki Nishimoto , I Tomohiro , Shunsuke Inenaga , Hideo Bannai , Masayuki Takeda

The fundamental question considered in algorithms on strings is that of indexing, that is, preprocessing a given string for specific queries. By now we have a number of efficient solutions for this problem when the queries ask for an exact…

Data Structures and Algorithms · Computer Science 2023-04-04 Paweł Gawrychowski , Garance Gourdel , Tatiana Starikovskaya , Teresa Anna Steiner

Although several grammar-based self-indexes have been proposed thus far, their applicability is limited to offline settings where whole input texts are prepared, thus requiring to rebuild index structures for given additional inputs, which…

Data Structures and Algorithms · Computer Science 2015-07-07 Yoshimasa Takabatake , Yasuo Tabei , Hiroshi Sakamoto

In this paper we are interested in indexing texts for substring matching queries with one edit error. That is, given a text $T$ of $n$ characters over an alphabet of size $\sigma$, we are asked to build a data structure that answers the…

Data Structures and Algorithms · Computer Science 2014-08-25 Djamal Belazzougui

Consider an input text string T[1,N] drawn from an unbounded alphabet. We study partial computation in suffix-based problems for Data Compression and Text Indexing such as (I) retrieve any segment of K<=N consecutive symbols from the…

Data Structures and Algorithms · Computer Science 2011-10-18 Gianni Franceschini , Roberto Grossi , S. Muthukrishnan

Shannon's entropy is a definitive lower bound for statistical compression. Unfortunately, no such clear measure exists for the compressibility of repetitive strings. Thus, ad hoc measures are employed to estimate the repetitiveness of…

Data Structures and Algorithms · Computer Science 2023-11-16 Giulia Bernardini , Gabriele Fici , Paweł Gawrychowski , Solon P. Pissis

Finding desired information from large data set is a difficult problem. Information retrieval is concerned with the structure, analysis, organization, storage, searching, and retrieval of information. Index is the main constituent of an IR…

Information Retrieval · Computer Science 2012-09-26 Md. Abdullah al Mamun , Md. Hanif , Md. Rakib Uddin , Tanvir Ahmed , Md. Mofizul Islam

It has been shown in the indexing literature that there is an essential difference between prefix/range searches on the one hand, and predecessor/rank searches on the other hand, in that the former provably allows faster query resolution.…

Data Structures and Algorithms · Computer Science 2018-04-16 Djamal Belazzougui , Paolo Boldi , Rasmus Pagh , Sebastiano Vigna

Compressed inverted indices in use today are based on the idea of gap compression: documents pointers are stored in increasing order, and the gaps between successive document pointers are stored using suitable codes which represent smaller…

Information Retrieval · Computer Science 2012-06-20 Sebastiano Vigna

Reranking, the process of refining the output from a first-stage retriever, is often considered computationally expensive, especially when using Large Language Models (LLMs). A common approach to mitigate this cost involves utilizing…

Information Retrieval · Computer Science 2026-04-30 Hervé Déjean , Stéphane Clinchant