The famous Černý conjecture, a 50-year-old mathematical problem, states that every n-state synchronizing automaton has a reset word of length at most (n− 1). We consider the question of finding short reset words. It is known that the exact version of the problem, i.e., finding the shortest reset word, is both NP -hard and coNP -hard, and actually complete for a class known as DP . It is also known that approximating the length of the shortest reset word within a factor of O(log n) is NP -hard… CONTINUE READING