Using BDDs with Combinations of Theories

  • Authors:
  • Pascal Fontaine;E. Pascal Gribomont

  • Affiliations:
  • -;-

  • Venue:
  • LPAR '02 Proceedings of the 9th International Conference on Logic for Programming, Artificial Intelligence, and Reasoning
  • Year:
  • 2002

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Abstract

A Boolean formula is unsatisfiable if and only if its representing binary decision diagram (BDD) is reduced to the single leaf "false". When BDD variables represent first-order atoms including equalities between terms, uninterpreted predicates or linear arithmetic constraints, a path to the "true" leaf in the BDD might not give a model. So BDDs representing unsatisfiable quantifier-free first-order logic formulas may not reduce to the single leaf "false". Decision procedures for combinations of theories can be used to eliminate all those unsatisfiable paths. In a naive approach every path would be considered; this would be very inefficient. We provide efficient algorithms to find general constraints (connections) from unsatisfiable paths to "true" in the BDD. Adding those connections to the BDD will eliminate many paths to "true" at one go. This procedure also ensures that no unnecessary constraint is added. In the context of invariant validation, this gives good results when using BDDs with a rich quantifier-free language.