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87
Translating pseudoboolean constraints into SAT
 Journal on Satisfiability, Boolean Modeling and Computation
, 2006
"... In this paper, we describe and evaluate three different techniques for translating pseudoboolean constraints (linear constraints over boolean variables) into clauses that can be handled by a standard SATsolver. We show that by applying a proper mix of translation techniques, a SATsolver can perfor ..."
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Cited by 181 (2 self)
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In this paper, we describe and evaluate three different techniques for translating pseudoboolean constraints (linear constraints over boolean variables) into clauses that can be handled by a standard SATsolver. We show that by applying a proper mix of translation techniques, a SATsolver can perform on a par with the best existing native pseudoboolean solvers. This is particularly valuable in those cases where the constraint problem of interest is naturally expressed as a SAT problem, except for a handful of constraints. Translating those constraints to get a pure clausal problem will take full advantage of the latest improvements in SAT research. A particularly interesting result of this work is the efficiency of sorting networks to express pseudoboolean constraints. Although tangential to this presentation, the result gives a suggestion as to how synthesis tools may be modified to produce arithmetic circuits more suitable for SAT based reasoning. Keywords: pseudoBoolean, SATsolver, SAT translation, integer linear programming
Error Explanation with Distance Metrics
 In Tools and Algorithms for the Construction and Analysis of Systems
, 2004
"... In the event that a system does not satisfy a speci cation, a model checker will typically automatically produce a counterexample trace that shows a particular instance of the undesirable behavior. ..."
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Cited by 83 (8 self)
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In the event that a system does not satisfy a speci cation, a model checker will typically automatically produce a counterexample trace that shows a particular instance of the undesirable behavior.
Type inference against races
 In SAS
, 2004
"... Abstract. The race condition checker rccjava uses a formal type system to statically identify potential race conditions in concurrent Java programs, but it requires programmersupplied type annotations. This paper describes a type inference algorithm for rccjava. Due to the interaction of parameteri ..."
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Cited by 51 (4 self)
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Abstract. The race condition checker rccjava uses a formal type system to statically identify potential race conditions in concurrent Java programs, but it requires programmersupplied type annotations. This paper describes a type inference algorithm for rccjava. Due to the interaction of parameterized classes and dependent types, this type inference problem is NPcomplete. This complexity result motivates our new approach to type inference, which is via reduction to propositional satisfiability. This paper describes our type inference algorithm and its performance on programs of up to 30,000 lines of code. 1
Satisfiability Solvers
, 2008
"... The past few years have seen an enormous progress in the performance of Boolean satisfiability (SAT) solvers. Despite the worstcase exponential run time of all known algorithms, satisfiability solvers are increasingly leaving their mark as a generalpurpose tool in areas as diverse as software and h ..."
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Cited by 48 (0 self)
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The past few years have seen an enormous progress in the performance of Boolean satisfiability (SAT) solvers. Despite the worstcase exponential run time of all known algorithms, satisfiability solvers are increasingly leaving their mark as a generalpurpose tool in areas as diverse as software and hardware verification [29–31, 228], automatic test pattern generation [138, 221], planning [129, 197], scheduling [103], and even challenging problems from algebra [238]. Annual SAT competitions have led to the development of dozens of clever implementations of such solvers [e.g. 13,
Solving MaxSAT as weighted CSP
, 2003
"... For the last ten years, a significant amount of work in the constraint community has been devoted to the improvement of complete methods for solving soft constraints networks. We wanted to see how recent progress in the weighted CSP (WCSP) field could compete with other approaches in related fie ..."
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Cited by 47 (12 self)
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For the last ten years, a significant amount of work in the constraint community has been devoted to the improvement of complete methods for solving soft constraints networks. We wanted to see how recent progress in the weighted CSP (WCSP) field could compete with other approaches in related fields.
Satbased answer set programming
 In Proc. AAAI04
, 2004
"... The relation between answer set programming (ASP) and propositional satisfiability (SAT) is at the center of many research papers, partly because of the tremendous performance boost of SAT solvers during last years. Various translations from ASP to SAT are known but the resulting SAT formula either ..."
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Cited by 45 (12 self)
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The relation between answer set programming (ASP) and propositional satisfiability (SAT) is at the center of many research papers, partly because of the tremendous performance boost of SAT solvers during last years. Various translations from ASP to SAT are known but the resulting SAT formula either includes many new variables or may have an unpractical size. There are also well known results showing a onetoone correspondence between the answer sets of a logic program and the models of its completion. Unfortunately, these results only work for specific classes of problems. In this paper we present a SATbased decision procedure for answer set programming that (i) deals with any (non disjunctive) logic program, (ii) works on a SAT formula without additional variables, and (iii) is guaranteed to work in polynomial space. Further, our procedure can be extended to compute all the answer sets still working in polynomial space. The experimental results of a prototypical implementation show that the approach can pay off sometimes by orders of magnitude.
Predicate Abstraction with Minimum Predicates
 In Advanced Research Working Conference on Correct Hardware Design and Verification Methods (CHARME
, 2003
"... Predicate abstraction is a popular abstraction technique employed in formal software verification. A crucial requirement to make predicate abstraction effective is to use as few predicates as possible, since the abstraction process is in the worst case exponential (in both time and memory requiremen ..."
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Cited by 37 (10 self)
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Predicate abstraction is a popular abstraction technique employed in formal software verification. A crucial requirement to make predicate abstraction effective is to use as few predicates as possible, since the abstraction process is in the worst case exponential (in both time and memory requirements) in the number of predicates involved. If a property can be proven to hold or not hold based on a given finite set of predicates P, the procedure we propose in this paper finds automatically a minimal subset of P that is sufficient for the proof. We explain how our technique can be used for more efficient verification of C programs. Our experiments show that predicate minimization can result in a significant reduction of both verification time and memory usage compared to earlier methods.
Efficient Verification of Sequential and Concurrent C Programs
, 2003
"... There has been considerable progress in the domain of software veri cation over the last few years. This advancement has been driven, to a large extent, by the emergence of powerful yet automated abstraction techniques like predicate abstraction. However, the state space explosion problem in model c ..."
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Cited by 36 (12 self)
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There has been considerable progress in the domain of software veri cation over the last few years. This advancement has been driven, to a large extent, by the emergence of powerful yet automated abstraction techniques like predicate abstraction. However, the state space explosion problem in model checking remains the chief obstacle to the practical veri cation of realworld distributed systems. Even in the case of purely sequential programs, a crucial requirement to make predicate abstraction eective is to use as few predicates as possible. This is because, in the worst case, the state space of the abstraction generated (and consequently the time and memory complexity of the abstraction process) is exponential in the number of predicates involved. In addition, for concurrent programs, the number of reachable states could grow exponentially with the number of components.
On SAT Modulo Theories and Optimization Problems
 In Theory and Applications of Satisfiability Testing (SAT), LNCS 4121
, 2006
"... Abstract. Solvers for SAT Modulo Theories (SMT) can nowadays handle large industrial (e.g., formal hardware and software verification) problems over theories such as the integers, arrays, or equality. Here we show that SMT approaches can also efficiently solve problems that, at first sight, do not h ..."
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Cited by 36 (4 self)
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Abstract. Solvers for SAT Modulo Theories (SMT) can nowadays handle large industrial (e.g., formal hardware and software verification) problems over theories such as the integers, arrays, or equality. Here we show that SMT approaches can also efficiently solve problems that, at first sight, do not have a typical SMT flavor. In particular, here we deal with SAT and SMT problems where models M are sought such that a given cost function f(M) is minimized. For this purpose, we introduce a variant of SMT where the theory T DPLL Modulo Theories framework. We discuss two different examples of applications of this SMT variant: weighted MaxSAT and weighted MaxSMT. We show how, with relatively little effort, one can obtain a competitive system that, in the case of weighted MaxSMT in the theory of Difference Logic, can even handle wellknown hard radio frequency assignment problems without any tailored heuristics. These results seem to indicate that MaxSAT/SMT techniques can already be used for realistic applications. 1
Explaining abstract counterexamples
 In Proc. of the International Symposium on Foundations of Software Engineering
, 2004
"... When a program violates its specification a model checker produces a counterexample that shows an example of undesirable behavior. It is up to the user to understand the error, locate it, and fix the problem. Previous work introduced a technique for explaining and localizing errors based on finding ..."
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Cited by 33 (6 self)
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When a program violates its specification a model checker produces a counterexample that shows an example of undesirable behavior. It is up to the user to understand the error, locate it, and fix the problem. Previous work introduced a technique for explaining and localizing errors based on finding the closest execution to a counterexample, with respect to a distance metric. That approach was applied only to concrete executions of programs. This paper extends and generalizes the approach by combining it with predicate abstraction. Using an abstract statespace increases scalability and makes explanations more informative. Differences between executions are presented in terms of predicates derived from the specification and program, rather than specific changes to variable values. Reasoning to the cause of an error from the fact that in the failing run x < y, but in the successful execution x = y is easier than reasoning from the information that in the failing run y = 239, but in the successful execution y = 232. An abstract explanation is automatically generalized. Predicate abstraction has previously been used in model checking purely as a statespace reduction technique. However, an abstraction good enough to enable a model checking tool to find an error is also likely to be useful as an automatically generated highlevel description of a state space — suitable for use by programmers. Results demonstrating the effectiveness of abstract explanations support this claim.