Finding Hard Instances of Satisfiability in Lukasiewicz Logics

One aspect that has been poorly studied in multiple-valued logics, and in particular in Lukasiewicz logics, is the generation of instances of varying difficulty for evaluating, comparing and improving satisfiability solvers. In this paper we present a new class of clausal forms, called Lukasiewicz (L-)clausal forms, motivate their usefulness, study their complexity, and report on an empirical investigation that shows an easy-hard-easy pattern and a phase transition phenomenon when testing the satisfiability of L-clausal forms.