Abstract
Searching on a line with Byzantine robots was first posed by Czyzowicz et al. in [13]: Suppose there are n robots searching on an infinite line to find a target which is unknown to the robots. At the beginning all robots stay at the origin and then they can start to search with maximum speed 1. Unfortunately, f of them are Byzantine fault, which means that they may ignore the target when passing it or lie that they find the target. Therefore, the target is found if at least \(f+1\) robots claim that they find the target at the same location. The aim is to design a parallel algorithm to minimize the competitive ratio S(n, f), the ratio between the time of finding the target and the distance from origin to the target in the worst case by n robots among which f are Byzantine fault.
In this paper, our main contribution is a new algorithm framework for solving the Byzantine robot searching problem with (n, f) sufficiently large. Under this framework, we design two specific algorithms to improve the previous upper bounds in [13] when \(f/n\in (0.358,0.382)\cup (0.413,0.5)\). Besides, we also improve the upper bound of S(n, f) for some small (n, f). Specifically, we improve the upper bound of S(6, 2) from 4 to 3.682, and the upper bound of S(3, 1) from 9 to 8.53.
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Sun, X., Sun, Y., Zhang, J. (2020). Better Upper Bounds for Searching on a Line with Byzantine Robots. In: Du, DZ., Wang, J. (eds) Complexity and Approximation. Lecture Notes in Computer Science(), vol 12000. Springer, Cham. https://doi.org/10.1007/978-3-030-41672-0_9
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