A tight lower bound for semi-synchronous collaborative grid exploration

Sebastian Brandt, Jara Uitto*, Roger Wattenhofer

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

7 Downloads (Pure)


Recently, there has been a growing interest in grid exploration by agents with limited capabilities. We show that the grid cannot be explored by three semi-synchronous finite automata, answering an open question by Emek et al. (Theor Comput Sci 608:255–267, 2015) in the negative. In the setting we consider, time is divided into discrete steps, where in each step, an adversarially selected subset of the agents executes one look–compute–move cycle. The agents operate according to a shared finite automaton, where every agent is allowed to have a distinct initial state. The only means of communication is to sense the states of the agents sharing the same grid cell. The agents are equipped with a global compass and whenever an agent moves, the destination cell of the movement is chosen by the agent’s automaton from the set of neighboring grid cells. In contrast to the four agent protocol by Emek et al., we show that three agents do not suffice for grid exploration.

Original languageEnglish
Pages (from-to)471-484
Number of pages14
Early online date1 Jan 2020
Publication statusPublished - Dec 2020
MoE publication typeA1 Journal article-refereed


  • Finite automata
  • Graph exploration
  • Mobile robots


Dive into the research topics of 'A tight lower bound for semi-synchronous collaborative grid exploration'. Together they form a unique fingerprint.

Cite this