An Explanation-Based Constraint Debugger

Constraints have become a central feature of advanced simulation-based verification. Effective debugging of constraints is an ongoing challenge. In this paper we present GenDebugger - an innovative GUI-based tool for debugging constraints. GenDebugger shows how a set of constraints is solved in a step by step flow, allowing the user to easily pick out steps that are key to the buggy behavior. It is unique in that it is designed for dealing with various types of constraint-related problems, not only constraint-conflicts or performance issues. GenDebugger utilizes principles from the explanation-based debug paradigm [1], in that it displays information justifying each step of the solution. A unique contribution is that it enables the user to easily combine separate explanations of individual steps into a comprehensive full explanation of the constraint-solver’s behavior. GenDebugger was lately released for full production, after an extensive process of evaluation with early access users. Our own experience and our users feedback indicate that GenDebugger provides highly valuable help in resolving problems found in constraints.