Fault-induced dynamics of oblivious robots on a line

Abstract

The study of computing in presence of faulty robots in the Look-Compute-Move model has been the object of extensive investigation, typically to design fault-tolerant algorithms.In this paper, we initiate a new line of investigation on the presence of faults, focusing on a different issue: we study, for the first time, the unintended dynamics of the robots when they execute an algorithm designed for a fault-free environment, in presence of undetectable crashed robots.We start this investigation considering a classical point-convergence algorithm for oblivious robots with limited visibility in a simple setting (which already presents serious challenges): synchronous robots on a line with at most two faults. Interestingly, the presence of faults induces the robots to perform some form of scattering, rather than point-convergence. In fact, we discover that they arrange themselves inside the segment delimited by the two faults in complex interleaved sequences of equidistant robots.