eng
Schloss Dagstuhl – Leibniz-Zentrum für Informatik
Leibniz International Proceedings in Informatics
1868-8969
2018-03-28
11:1
11:16
10.4230/LIPIcs.OPODIS.2017.11
article
Evacuating an Equilateral Triangle in the Face-to-Face Model
Chuangpishit, Huda
Mehrabi, Saeed
Narayanan, Lata
Opatrny, Jaroslav
Consider k robots initially located at the centroid of an equilateral triangle T of sides of length one. The goal of the robots is to evacuate T through an exit at an unknown location on the boundary of T. Each robot can move anywhere in T independently of other robots with maximum speed one. The objective is to minimize the evacuation time, which is defined as the time required for all k robots to reach the exit. We consider the face-to-face communication model for the robots: a robot can communicate with another robot only when they meet in T.
In this paper, we give upper and lower bounds for the face-to-face evacuation time by k robots. We show that for any k, any algorithm for evacuating k >= 1 robots from T requires at least sqrt(3) time. This bound is asymptotically optimal, as we show that a straightforward strategy of evacuation by k robots gives an upper bound of sqrt(3) + 3/k. For k = 3, 4, 5, 6, we
show significant improvements on the obvious upper bound by giving algorithms with evacuation times of 2.0887, 1.9816, 1.876, and 1.827, respectively. For k = 2 robots, we give a lower bound of 1 + 2/sqrt(3) ~= 2.154, and an algorithm with upper bound of 2.3367 on the evacuation time.
https://drops.dagstuhl.de/storage/00lipics/lipics-vol095-opodis2017/LIPIcs.OPODIS.2017.11/LIPIcs.OPODIS.2017.11.pdf
Distributed algorithms
Robots evacuation
Face-to-face communication
Equilateral triangle