Zaher S. Andraus

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This paper describes a new algorithm for extracting unsatisfiable subformulas from a given unsatisfiable CNF formula. Such unsatisfiable "cores" can be very helpful in diagnosing the causes of infeasibility in large systems. Our algorithm is unique in that it adapts the "learning process" of a modern SAT solver to identify unsatisfiable subformulas rather(More)
Abstraction plays a critical role in verifying complex sys-tems. A number of languages have been proposed to model hardware systems by, primarily, abstracting away their wide datapaths while keeping the low-level details of their control logic. This leads to a significant reduction in the size of the state space and makes it possible to verify intricate(More)
In this paper we explore the application of Counter example-Guided Abstraction Refinement (CEGAR) in the context of microprocessor correspondence checking. The approach utilizes automatic datapath abstraction, augmented with automatic refinement based on 1) localization, 2) generalization, and 3) minimal unsatisfiable subset (MUS) extraction. We introduce(More)
We describe the Reveal formal functional verification system and its application to four representative hardware test cases. Reveal employs counterexample-guided abstraction refinement, or CEGAR, and is suitable for verifying the complex control logic of designs with wide datapaths. Reveal performs automatic datapath abstraction yielding an approximation of(More)
We describe the application of the Reveal formal functional verification system to six representative hardware test cases. Reveal employs counterexample-guided abstraction refinement, or CEGAR, and is suitable for verifying the complex control logic of designs with wide datapaths. Reveal performs automatic datapath abstraction yielding an approximation of(More)
We tackle the problem of finding a smallest-cardinality MUS (SMUS) of a given formula. The SMUS provides a succinct explanation of infeasibility and is valuable for applications that rely on such explanations. We present a branch-and-bound algorithm that utilizes iterative MAXSAT solutions to generate lower and upper bounds on the size of the SMUS, and(More)
Explaining the causes of infeasibility of Boolean formulas has practical applications in numerous fields, such as artificial intelligence (repairing inconsistent knowledge bases), formal verification (abstraction refinement and unbounded model checking), and electronic design (diagnosing and correcting infeasibility). Minimal unsatisfiable subformulas(More)
The recent improvements in SAT solving algorithms, driven by the quest to solve increasingly complex problem instances, has produced techniques whose objective is to prune large portions of the search space to converge quickly to a solution (for instance, conflict-driven learning). In particular, solutions have been suggested in this area which attack the(More)
This report describes a strong connection between maximum satisfiability and minimally-unsatisfiable subfor-mulas of any constraint system, as well as techniques for exploiting it. Focusing on CNF formulas, we explore this relationship and present novel algorithms for extracting minimally-unsatisfiable subformulas, including one that finds all such(More)
As mobile, handheld devices have increased in power and function, users increasingly treat them not as mere organizers, but as an extension of their personal computing environment. But accessing files remotely can lead to poor performance, due to network latency. While caching can alleviate this problem, existing caching schemes were designed for desktop(More)