2026-07-24T17:11:56Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:13954 2024-03-06T10:52:59Z ddc:004 open_access

On-Line Pattern Matching on D-Texts (Invited Talk) Pisanti, Nadia pattern matching elastic-degenerate string matrix multiplication The Elastic Degenerate String Matching (EDSM) problem is defined as that of finding an occurrence of a pattern P of length m in an ED-text T. A D-text (Degenerate text) is a string that actually represents a set of similar and aligned strings (e.g. a pan-genome [The Computational Pan-Genomics Consortium, 2018]) by collapsing common fragments into a standard string, and representing variants with sets of alternative substrings. When such substrings are not bound to have the same size, then we talk about elastic D-strings (ED-strings). In [R.Grossi et al., 2017] we gave an O(nm²+N) time on-line algorithm for EDSM, where n is the length of T and N is its size, defined as the total number of letters. A fundamental toolkit of our algorithm is the O(m²+N) time solution of the later called Active Prefixes problem (AP). In [K.Aoyama et al., 2018], a O(m^{1.5} √{log m}+N) solution for AP was shown, leading to a O(nm^{1.5} √{log m}+N) time solution for EDSM. The natural open problem was thus whether the 1.5 exponent could furtherly be decreased. In [G.Bernardini et al., 2019], we prove several properties that answer this and other questions: we give a conditional O(nm^{1.5}+N) lower bound for EDSM, proving that a combinatorial algorithm solving EDSM in O(nm^{1.5-ε} +N) time would break the Boolean Matrix Multiplication (BMM) conjecture; we use this result as a hint to devise a non-combinatorial algorithm that solves EDSM in O(nm^{1.381}+N) time; we do so by successfully combining Fast Fourier Transform and properties of string periodicity. In my talk I will overview the results above, as well as some interesting side results: the extension to a dictionary rather than a single pattern [S.P.Pissis and A.Retha, 2018], the introduction of errors [G.Bernardini et al., 2020], and a notion of matching among D-strings with its linear time solution [M.Alzamel et al., 2020]. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Nadia Pisanti 2021 Is Part Of LIPIcs, Volume 191, 32nd Annual Symposium on Combinatorial Pattern Matching (CPM 2021) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.CPM.2021.3 urn:nbn:de:0030-drops-139548 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CPM.2021.3 eng https://creativecommons.org/licenses/by/4.0/legalcode