Optimal Distance Labeling for Permutation Graphs

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Main Authors: Gawrychowski, Paweł, Janczewski, Wojciech
Format: Preprint
Published: 2024
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author Gawrychowski, Paweł
Janczewski, Wojciech
author_facet Gawrychowski, Paweł
Janczewski, Wojciech
contents A permutation graph is the intersection graph of a set of segments between two parallel lines. In other words, they are defined by a permutation $π$ on $n$ elements, such that $u$ and $v$ are adjacent if an only if $u<v$ but $π(u)>π(v)$. We consider the problem of computing the distances in such a graph in the setting of informative labeling schemes. The goal of such a scheme is to assign a short bitstring $\ell(u)$ to every vertex $u$, such that the distance between $u$ and $v$ can be computed using only $\ell(u)$ and $\ell(v)$, and no further knowledge about the whole graph (other than that it is a permutation graph). This elegantly captures the intuition that we would like our data structure to be distributed, and often leads to interesting combinatorial challenges while trying to obtain lower and upper bounds that match up to the lower-order terms. For distance labeling of permutation graphs on $n$ vertices, Katz, Katz, and Peleg [STACS 2000] showed how to construct labels consisting of $\mathcal{O}(\log^{2} n)$ bits. Later, Bazzaro and Gavoille [Discret. Math. 309(11)] obtained an asymptotically optimal bounds by showing how to construct labels consisting of $9\log{n}+\mathcal{O}(1)$ bits, and proving that $3\log{n}-\mathcal{O}(\log{\log{n}})$ bits are necessary. This however leaves a quite large gap between the known lower and upper bounds. We close this gap by showing how to construct labels consisting of $3\log{n}+\mathcal{O}(\log\log n)$ bits.
format Preprint
id arxiv_https___arxiv_org_abs_2407_12147
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Optimal Distance Labeling for Permutation Graphs
Gawrychowski, Paweł
Janczewski, Wojciech
Data Structures and Algorithms
A permutation graph is the intersection graph of a set of segments between two parallel lines. In other words, they are defined by a permutation $π$ on $n$ elements, such that $u$ and $v$ are adjacent if an only if $u<v$ but $π(u)>π(v)$. We consider the problem of computing the distances in such a graph in the setting of informative labeling schemes. The goal of such a scheme is to assign a short bitstring $\ell(u)$ to every vertex $u$, such that the distance between $u$ and $v$ can be computed using only $\ell(u)$ and $\ell(v)$, and no further knowledge about the whole graph (other than that it is a permutation graph). This elegantly captures the intuition that we would like our data structure to be distributed, and often leads to interesting combinatorial challenges while trying to obtain lower and upper bounds that match up to the lower-order terms. For distance labeling of permutation graphs on $n$ vertices, Katz, Katz, and Peleg [STACS 2000] showed how to construct labels consisting of $\mathcal{O}(\log^{2} n)$ bits. Later, Bazzaro and Gavoille [Discret. Math. 309(11)] obtained an asymptotically optimal bounds by showing how to construct labels consisting of $9\log{n}+\mathcal{O}(1)$ bits, and proving that $3\log{n}-\mathcal{O}(\log{\log{n}})$ bits are necessary. This however leaves a quite large gap between the known lower and upper bounds. We close this gap by showing how to construct labels consisting of $3\log{n}+\mathcal{O}(\log\log n)$ bits.
title Optimal Distance Labeling for Permutation Graphs
topic Data Structures and Algorithms
url https://arxiv.org/abs/2407.12147