Label-Guided Graph Exploration with Adjustable Ratio of Labels

TL;DR

This paper introduces a flexible 1-bit label scheme for graph exploration, allowing adjustable label ratios, which enables efficient exploration of complex graphs with minimal memory and adaptable labeling costs.

Contribution

It proposes a novel 1-bit labeling scheme with adjustable label ratios for graph exploration, extending previous work to more complex graphs and providing explicit algorithms and bounds.

Findings

Label ratio can be tuned to balance exploration cost and label maintenance.

Exploration time depends on maximum degree and label ratio, with explicit bounds.

The scheme works on graphs with loops and multiple edges, unlike previous simple graph focus.

Abstract

The graph exploration problem is to visit all the nodes of a connected graph by a mobile entity, e.g., a robot. The robot has no a priori knowledge of the topology of the graph or of its size. Cohen et al. \cite{Ilcinkas08} introduced label guided graph exploration which allows the system designer to add short labels to the graph nodes in a preprocessing stage; these labels can guide the robot in the exploration of the graph. In this paper, we address the problem of adjustable 1-bit label guided graph exploration. We focus on the labeling schemes that not only enable a robot to explore the graph but also allow the system designer to adjust the ratio of the number of different labels. This flexibility is necessary when maintaining different labels may have different costs or when the ratio is pre-specified. We present 1-bit labeling (two colors, namely black and white) schemes for this problem along with a labeling algorithm for generating the required labels. Given an $n$-node graph and a rational number $\rho$, we can design a 1-bit labeling scheme such that $n/b\geq \rho$ where $b$ is the number of nodes labeled black. The robot uses $O(\rho\log\Delta)$ bits of memory for exploring all graphs of maximum degree $\Delta$. The exploration is completed in time $O(n\Delta^{\frac{16\rho+7}{3}}/\rho+\Delta^{\frac{40\rho+10}{3}})$. Moreover, our labeling scheme can work on graphs containing loops and multiple edges, while that of Cohen et al. focuses on simple graphs.