Optimal Hardness of Online Algorithms for Large Common Induced Subgraphs

Fuente: arXiv
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Autori principali: Gamarnik, David, Rácz, Miklós Z., Schoenbach, Gabe
Natura: Preprint
Pubblicazione: 2026
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author Gamarnik, David
Rácz, Miklós Z.
Schoenbach, Gabe
author_facet Gamarnik, David
Rácz, Miklós Z.
Schoenbach, Gabe
contents We study the problem of efficiently finding large common induced subgraphs of two independent Erdős--Rényi random graphs $G_1, G_2 \sim \mathbb{G}(n,1/2)$. Recently, Chatterjee and Diaconis showed that the largest common induced subgraph of $G_1$ and $G_2$ has size $(4-o(1))\log_2 n$ with high probability. We first show that a simple greedy online algorithm finds a common induced subgraph of $G_1$ and $G_2$ of size $(2-o(1)) \log_2 n$ with high probability. Our main result shows that no online algorithm can find a common induced subgraph of $G_1$ and $G_2$ of size at least $(2+\varepsilon) \log_2 n$ with probability bounded away from $0$ as $n \to \infty$. Together, these results provide evidence that this problem exhibits a computation-to-optimization gap. To prove the impossibility result, we show that the solution space of the problem exhibits a version of the (multi) overlap gap property (OGP), and utilize an interpolation argument recently developed by Gamarnik, Kizildağ, and Warnke that connects OGP and online algorithms.
format Preprint
id arxiv_https___arxiv_org_abs_2605_03893
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Optimal Hardness of Online Algorithms for Large Common Induced Subgraphs
Gamarnik, David
Rácz, Miklós Z.
Schoenbach, Gabe
Data Structures and Algorithms
Computational Complexity
Discrete Mathematics
Combinatorics
Probability
We study the problem of efficiently finding large common induced subgraphs of two independent Erdős--Rényi random graphs $G_1, G_2 \sim \mathbb{G}(n,1/2)$. Recently, Chatterjee and Diaconis showed that the largest common induced subgraph of $G_1$ and $G_2$ has size $(4-o(1))\log_2 n$ with high probability. We first show that a simple greedy online algorithm finds a common induced subgraph of $G_1$ and $G_2$ of size $(2-o(1)) \log_2 n$ with high probability. Our main result shows that no online algorithm can find a common induced subgraph of $G_1$ and $G_2$ of size at least $(2+\varepsilon) \log_2 n$ with probability bounded away from $0$ as $n \to \infty$. Together, these results provide evidence that this problem exhibits a computation-to-optimization gap. To prove the impossibility result, we show that the solution space of the problem exhibits a version of the (multi) overlap gap property (OGP), and utilize an interpolation argument recently developed by Gamarnik, Kizildağ, and Warnke that connects OGP and online algorithms.
title Optimal Hardness of Online Algorithms for Large Common Induced Subgraphs
topic Data Structures and Algorithms
Computational Complexity
Discrete Mathematics
Combinatorics
Probability
url https://arxiv.org/abs/2605.03893