The aim of the paper is to provide a formalization of the notion of parallelism of a marked graph exploitable by parallel simulation. We show that there exists an optimal starting point for equational simulations which gives a speed of simulation in the order of the intrinsic sequentiality of the system. Furthermore, under few assumptions, the modification of the marking will accelerate the simulation without altering its results for the stationary regime. We also derive algorithms to compute this optimal marking.