A Rearrangement Search Strategy for Determining Propositional Satis ability

We present a simple algorithm for determining the satis ability of propositional formulas in Con junctive Normal Form As the procedure searches for a satisfying truth assignment it dynamically rearranges the order in which variables are con sidered The choice of which variable to assign a truth value next is guided by an upper bound on the size of the search remaining the procedure makes the choice which yields the smallest upper bound on the size of the remaining search We describe several upper bound functions and dis cuss the tradeo between accurate upper bound functions and the overhead required to compute the upper bounds Experimental data shows that for one easily computed upper bound the reduc tion in the size of the search space more than compensates for the overhead involved in select ing the next variable