Approximating Text-To-Pattern Distance via Dimensionality Reduction

Author Przemysław Uznański

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Przemysław Uznański
  • Institute of Computer Science, University of Wrocław, Poland

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Przemysław Uznański. Approximating Text-To-Pattern Distance via Dimensionality Reduction. In 31st Annual Symposium on Combinatorial Pattern Matching (CPM 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 161, pp. 29:1-29:11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


Text-to-pattern distance is a fundamental problem in string matching, where given a pattern of length m and a text of length n, over an integer alphabet, we are asked to compute the distance between pattern and the text at every location. The distance function can be e.g. Hamming distance or 𝓁_p distance for some parameter p > 0. Almost all state-of-the-art exact and approximate algorithms developed in the past ∼ 40 years were using FFT as a black-box. In this work we present 𝒪~(n/ε²) time algorithms for (1±ε)-approximation of 𝓁₂ distances, and 𝒪~(n/ε³) algorithm for approximation of Hamming and 𝓁₁ distances, all without use of FFT. This is independent to the very recent development by Chan et al. [STOC 2020], where 𝒪(n/ε²) algorithm for Hamming distances not using FFT was presented - although their algorithm is much more "combinatorial", our techniques apply to other norms than Hamming.

Subject Classification

ACM Subject Classification
  • Theory of computation → Sketching and sampling
  • Theory of computation → Approximation algorithms analysis
  • Approximate Pattern Matching
  • 𝓁₂ Distance
  • 𝓁₁ Distance
  • Hamming Distance
  • Approximation Algorithms
  • Combinatorial Algorithms


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