Efficient satisfiability modulo theories via delayed theory combination

  • Authors:
  • Marco Bozzano;Roberto Bruttomesso;Alessandro Cimatti;Tommi Junttila;Silvio Ranise;Peter van Rossum;Roberto Sebastiani

  • Affiliations:
  • ITC-IRST, Povo, Trento, Italy;ITC-IRST, Povo, Trento, Italy;ITC-IRST, Povo, Trento, Italy;Helsinki University of Technology, Finland;LORIA and INRIA-Lorraine, Villers les Nancy, France;Radboud University, Nijmegen, The Netherlands;DIT, Università di Trento, Italy

  • Venue:
  • CAV'05 Proceedings of the 17th international conference on Computer Aided Verification
  • Year:
  • 2005

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Abstract

The problem of deciding the satisfiability of a quantifier-free formula with respect to a background theory, also known as Satisfiability Modulo Theories (SMT), is gaining increasing relevance in verification: representation capabilities beyond propositional logic allow for a natural modeling of real-world problems (e.g., pipeline and RTL circuits verification, proof obligations in software systems). In this paper, we focus on the case where the background theory is the combination T1∪T2 of two simpler theories. Many SMT procedures combine a boolean model enumeration with a decision procedure for T1∪T2, where conjunctions of literals can be decided by an integration schema such as Nelson-Oppen, via a structured exchange of interface formulae (e.g., equalities in the case of convex theories, disjunctions of equalities otherwise). We propose a new approach for SMT(T1∪T2), called Delayed Theory Combination, which does not require a decision procedure for T1∪T2, but only individual decision procedures for T1 and T2, which are directly integrated into the boolean model enumerator. This approach is much simpler and natural, allows each of the solvers to be implemented and optimized without taking into account the others, and it nicely encompasses the case of non-convex theories. We show the effectiveness of the approach by a thorough experimental comparison.