Computer Science Department
School of Computer Science, Carnegie Mellon University


Optimizing Symbolic Model Checking for Constraint-Rich Models

Bwolen Yang, Reid Simmons, Randal E. Bryant, David R. O'Hallaron

March 1999

A condensed version of this technical report will appear in
Proceedings of the International Conference on Computer-Aided Verification, Trento, Italy, July 1999.

Keywords: Symbolic model checking, Binary Decision Diagram (BDD), time-invariant constraints, redundant state-variable elimination, macro

This paper presents optimizations for verifying systems with complex time-invariant constraints. These constraints arise naturally from modeling physical systems, e.g., in establishing the relationship between different components in a system. To verify constraint-rich systems, we propose two new optimizations. The first optimization is a simple, yet powerful, extension of the conjunctive-partitioning algorithm. The second is a collection of BDD-based macro-extraction and macro-expansion algorithms to remove state variables. We show that these two optimizations are essential in verifying constraint-rich problems; in particular, this work has enabled the verification of fault diagnosis models of the Nomad robot (an Antarctic meteorite explorer) and of the NASA Deep Space One spacecraft.

25 pages

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