Beyond quantifier-free interpolation in extensions of Presburger arithmetic

  • Authors:
  • Angelo Brillout;Daniel Kroening;Philipp Rümmer;Thomas Wahl

  • Affiliations:
  • ETH Zurich, Switzerland;Oxford University Computing Laboratory, United Kingdom;Oxford University Computing Laboratory, United Kingdom;Oxford University Computing Laboratory, United Kingdom

  • Venue:
  • VMCAI'11 Proceedings of the 12th international conference on Verification, model checking, and abstract interpretation
  • Year:
  • 2011

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Abstract

Craig interpolation has emerged as an effective means of generating candidate program invariants. We present interpolation procedures for the theories of Presburger arithmetic combined with (i) uninterpreted predicates (QPA+UP), (ii) uninterpreted functions (QPA+UF) and (iii) extensional arrays (QPA+AR). We prove that none of these combinations can be effectively interpolated without the use of quantifiers, even if the input formulae are quantifier-free. We go on to identify fragments of QPA+UP and QPA+UF with restricted forms of guarded quantification that are closed under interpolation. Formulae in these fragments can easily be mapped to quantifier-free expressions with integer division. For QPA+AR, we formulate a sound interpolation procedure that potentially produces interpolants with unrestricted quantifiers.