Automatic generation of invariants for circular derivations in SUP(LA)

  • Authors:
  • Arnaud Fietzke;Evgeny Kruglov;Christoph Weidenbach

  • Affiliations:
  • Max-Planck-Institut für Informatik, Saarbrücken, Germany and Computer Science, Saarland University, Saarbrücken, Germany;Max-Planck-Institut für Informatik, Saarbrücken, Germany and Computer Science, Saarland University, Saarbrücken, Germany;Max-Planck-Institut für Informatik, Saarbrücken, Germany and Computer Science, Saarland University, Saarbrücken, Germany

  • Venue:
  • LPAR'12 Proceedings of the 18th international conference on Logic for Programming, Artificial Intelligence, and Reasoning
  • Year:
  • 2012

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Abstract

The hierarchic combination of linear arithmetic and first-order logic with free function symbols, FOL(LA), results in a strictly more expressive logic than its two parts. The SUP(LA) calculus can be turned into a decision procedure for interesting fragments of FOL(LA). For example, reachability problems for timed automata can be decided by SUP(LA) using an appropriate translation into FOL(LA). In this paper, we extend the SUP(LA) calculus with an additional inference rule, automatically generating inductive invariants from partial SUP(LA) derivations. The rule enables decidability of more expressive fragments, including reachability for timed automata with unbounded integer variables. We have implemented the rule in the SPASS(LA) theorem prover with promising results, showing that it can considerably speed up proof search and enable termination of saturation for practically relevant problems.