Tight bound on Johnson´s algorithm for Max-SAT

We present a new technique that gives a more thorough analysis on Johnson´s classical algorithm for the maximum satisfiability problem. In contrast to the common belief for two decades that Johnson´s algorithm has performance ratio 1/2, we show that the performance ratio is 2/3, and that this bound is tight. Moreover we show that simple generalizations of Johnson´s algorithm do not improve the performance ratio bound 2/3