Diverse beam search to find densest-known planar unit distance graphs

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Hauptverfasser: Engel, Peter, Hammond-Lee, Owen, Su, Yiheng, Varga, Dániel, Zsámboki, Pál
Format: Preprint
Veröffentlicht: 2024
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author Engel, Peter
Hammond-Lee, Owen
Su, Yiheng
Varga, Dániel
Zsámboki, Pál
author_facet Engel, Peter
Hammond-Lee, Owen
Su, Yiheng
Varga, Dániel
Zsámboki, Pál
contents This paper addresses the problem of determining the maximum number of edges in a unit distance graph (UDG) of $n$ vertices using computer search. An unsolved problem of Paul Erdős asks the maximum number of edges $u(n)$ a UDG of $n$ vertices can have. Those UDGs that attain $u(n)$ are called "maximally dense." In this paper, we seek to demonstrate a computer algorithm to generate dense UDGs for vertex counts up to at least 100. Via beam search with an added visitation metric, our algorithm finds all known maximally dense UDGs up to isomorphism at the push of a button. In addition, for $15 < n$, where $u(n)$ is unknown, i) the algorithm finds all previously published densest UDGs up to isomorphism for $15 < n \le 30$, and ii) the rate of growth of $u(n)/n$ remains similar for $30 < n$. The code and database of over 60 million UDGs found by our algorithm can be found at https://codeberg.org/zsamboki/dbs-udg.
format Preprint
id arxiv_https___arxiv_org_abs_2406_15317
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Diverse beam search to find densest-known planar unit distance graphs
Engel, Peter
Hammond-Lee, Owen
Su, Yiheng
Varga, Dániel
Zsámboki, Pál
Combinatorics
Discrete Mathematics
Metric Geometry
This paper addresses the problem of determining the maximum number of edges in a unit distance graph (UDG) of $n$ vertices using computer search. An unsolved problem of Paul Erdős asks the maximum number of edges $u(n)$ a UDG of $n$ vertices can have. Those UDGs that attain $u(n)$ are called "maximally dense." In this paper, we seek to demonstrate a computer algorithm to generate dense UDGs for vertex counts up to at least 100. Via beam search with an added visitation metric, our algorithm finds all known maximally dense UDGs up to isomorphism at the push of a button. In addition, for $15 < n$, where $u(n)$ is unknown, i) the algorithm finds all previously published densest UDGs up to isomorphism for $15 < n \le 30$, and ii) the rate of growth of $u(n)/n$ remains similar for $30 < n$. The code and database of over 60 million UDGs found by our algorithm can be found at https://codeberg.org/zsamboki/dbs-udg.
title Diverse beam search to find densest-known planar unit distance graphs
topic Combinatorics
Discrete Mathematics
Metric Geometry
url https://arxiv.org/abs/2406.15317