In [4] , the authors look at probabilistic bounds and solutions for the exploration of anonymous unoriented rings of any size by a cohort of robots. Considering identical, oblivious, and probabilistic robots, they show that at least four of them are necessary to solve the problem. Moreover, they give a randomized protocol for four robots working in any ring of size more than eight. Here we close the question of optimal (w.r.t. the cohort size) ring exploration by probabilistic robots. Indeed, we propose a protocol for four robots working in any ring of size less or equal to eight. Composing this protocol with the one in [4], we obtain a protocol for any ring-size.
In REF an optimal algorithm for the probabilistic exploration of rings of size smaller than eight was given.
Optimal exploration of small rings
WRAS '10
Mathematics Computer Science