On the Cost of Simulating a Parallel Boolean Automata Network by a Block-Sequential One

In this article we study the minimum number κ of additional automata that a Boolean automata network (BAN) associated with a given blocksequential update schedule needs in order to simulate a given BAN with a parallel update schedule. We introduce a graph that we call NECC graph built from the BAN and the update schedule. We show the relation between κ and the chromatic number of the NECC graph. Thanks to this NECC graph, we bound κ in the worst case between n/2 and 2n/3 + 2 (n being the size of the BAN simulated) and we conjecture that this number equals n/2. We support this conjecture with two results: the clique number of a NECC graph is always less than or equal to n/2 and, for the subclass of bijective BANs, κ is always less than or equal to n/2 + 1.