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Towards an understanding of hillclimbing procedures for SAT
 In Proceedings of AAAI93
, 1993
"... Recently several local hillclimbing procedures for propositional satisability havebeen proposed, which are able to solve large and di cult problems beyond the reach ofconventional algorithms like DavisPutnam. By the introduction of some new variants of these procedures, we provide strong experimen ..."
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Cited by 138 (6 self)
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Recently several local hillclimbing procedures for propositional satisability havebeen proposed, which are able to solve large and di cult problems beyond the reach ofconventional algorithms like DavisPutnam. By the introduction of some new variants of these procedures, we provide strong experimental evidence to support the conjecture that neither greediness nor randomness is important in these procedures. One of the variants introduced seems to o er signi cant improvements over earlier procedures. In addition, we investigate experimentally how their performance depends on their parameters. Our results suggest that runtime scales less than simply exponentially in the problem size. 1
Tabu Search for SAT
 In Proceedings of AAAI’97
"... In this paper, tabu search for SAT is investigated from an experimental point of view. To this end, TSAT, a basic tabu search algorithm for SAT, is introduced and compared with Selman et al. Random Walk Strategy GSAT procedure, in short RWSGSAT. TSAT does not involve the additional ..."
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Cited by 48 (2 self)
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In this paper, tabu search for SAT is investigated from an experimental point of view. To this end, TSAT, a basic tabu search algorithm for SAT, is introduced and compared with Selman et al. Random Walk Strategy GSAT procedure, in short RWSGSAT. TSAT does not involve the additional
Using Global Constraints for Local Search
 DIMACS SERIES IN DISCRETE MATHEMATICS AND THEORETICAL COMPUTER SCIENCE
, 2000
"... Conventional ways of using local search are difficult to generalize. Increased efficiency is the only goal, generality often being disregarded. This is manifested in the highly monolithic encodings of complex problems and the application of highly specific satisfaction methods. Other approaches tak ..."
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Cited by 28 (9 self)
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Conventional ways of using local search are difficult to generalize. Increased efficiency is the only goal, generality often being disregarded. This is manifested in the highly monolithic encodings of complex problems and the application of highly specific satisfaction methods. Other approaches take the general constraint programming framework as a starting point and try to introduce local search methods for constraint satisfaction. These methods frequently fail because they have only a very limited view of the unknown searchspace structure. The present paper attempts to overcome the drawbacks of these two approaches by using global constraints. The use of global constraints for local search allows us to revise a current state on a more global level with domainspecific knowledge, while preserving features like reusability and maintenance. The proposed strategy is demonstrated on a dynamic jobshop scheduling problem.
A branch and cut algorithm for maxsat and weighted maxsat
 SATISFIABILITY PROBLEM: THEORY AND APPLICATIONS, VOLUME 35 OF DIMACS SERIES ON DISCRETE MATHEMATICS AND THEORETICAL COMPUTER SCIENCE
, 1997
"... We describe a branch and cut algorithm for both MAXSAT and weighted MAXSAT. This algorithm uses the GSAT procedure as a primal heuristic. At each nodewe solve a linear programming (LP) relaxation of the problem. Two styles of separating cuts are added: resolution cuts and odd cycle inequalities. ..."
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Cited by 14 (0 self)
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We describe a branch and cut algorithm for both MAXSAT and weighted MAXSAT. This algorithm uses the GSAT procedure as a primal heuristic. At each nodewe solve a linear programming (LP) relaxation of the problem. Two styles of separating cuts are added: resolution cuts and odd cycle inequalities. We compare our algorithm to an extension of the Davis Putnam Loveland (EDPL) algorithm. Our algorithm is more e ective than EDPL on some problems, notably MAX2SAT. EDPL is more e ective on some other classes of problems.
A Modular Partitioning Approach for Asynchronous Circuit Synthesis
 In Proc. ACM/IEEE Design Automation Conference
, 1994
"... Asynchronous circuits are widely used in many real time applications such as digital communication and computer systems. The design of complex asynchronous circuits is a di cult and errorprone task. An adequate synthesis method will signi cantly simplify the design and reduce errors. In this paper, ..."
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Cited by 12 (2 self)
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Asynchronous circuits are widely used in many real time applications such as digital communication and computer systems. The design of complex asynchronous circuits is a di cult and errorprone task. An adequate synthesis method will signi cantly simplify the design and reduce errors. In this paper, we present a general and e cient partitioning approach to the synthesis of asynchronous circuits from general Signal Transition Graph (STG) speci cations. The method partitions a large signal transition graph into smaller and manageable subgraphs which signi cantly reduces the complexity of asynchronous circuit synthesis. Experimental results of our partitioning approach with large number of practical industrial asynchronous circuit benchmarks are presented. They show that, compared to the existing asynchronous circuit synthesis techniques, this partitioning approach achieves many orders of magnitude of performance improvements in terms of computing time, in addition to the reduced circuit implementation area. This lends itself well to practical asynchronous circuit synthesis from general STG speci cations.
Solving MAXSAT and Weighted MAXSAT Problems Using BranchandCut
, 1998
"... We describe a branch and cut algorithm for both MAXSAT and weighted MAXSAT. This algorithm uses the GSAT procedure as a primal heuristic. At each nodewe solve a linear programming (LP) relaxation of the problem. Two styles of separating cuts are added: resolution cuts and odd cycle inequalities. W ..."
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Cited by 5 (2 self)
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We describe a branch and cut algorithm for both MAXSAT and weighted MAXSAT. This algorithm uses the GSAT procedure as a primal heuristic. At each nodewe solve a linear programming (LP) relaxation of the problem. Two styles of separating cuts are added: resolution cuts and odd cycle inequalities. We compare our algorithm to an extension of the Davis Putnam Loveland (EDPL) algorithm and a SemiDefinite Programming (SDP) approach. Our algorithm is more effective than EDPL on some problems, notably MAX2SAT. EDPL and SDP are more effective on some other classes of problems.
GSAT: A new method for solving hard satisfiability problems
, 1992
"... We introduce a greedy local search procedure called GSAT for solving propositional satis ability problems. Our experiments show that this procedure can be used to solve hard, randomly generated problems that are an order of magnitude larger than those that can be handled by more traditional approach ..."
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Cited by 2 (0 self)
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We introduce a greedy local search procedure called GSAT for solving propositional satis ability problems. Our experiments show that this procedure can be used to solve hard, randomly generated problems that are an order of magnitude larger than those that can be handled by more traditional approaches such as the DavisPutnam procedure or resolution. We also show that GSAT can solve structured satisfiability problems quickly. In particular, we solve encodings of graph coloring problems, Nqueens, and Boolean induction. General application strategies and limitations of the approach are also discussed. GSAT is best viewed as a modelfinding procedure. Its good performance suggests that it may beadvantageous to reformulate reasoning tasks that have traditionally been viewed as theoremproving problems as modelfinding tasks.
A BDD SAT Solver for Satisfiability Testing: A Case Study
, 1993
"... The satisfiability problem (SAT) is a fundamental problem in mathematical logic, constraint satisfaction, VLSI engineering, and computing theory. Methods to solve the satisfiability problem play an important role in the development of computing theory and systems. In this paper, we give a BDD (Binar ..."
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The satisfiability problem (SAT) is a fundamental problem in mathematical logic, constraint satisfaction, VLSI engineering, and computing theory. Methods to solve the satisfiability problem play an important role in the development of computing theory and systems. In this paper, we give a BDD (Binary Decision Diagrams) SAT solver for practical asynchronous circuit design. The BDD SAT solver consists of a structural SAT formula preprocessor and a complete, incremental SAT algorithm that is able to nd an optimal solution. The preprocessor compresses a large size SAT formula representing the circuit into a number of smaller SAT formulas. This avoids the problem of solving very large SAT formulas. Each small size SAT formula is solved by the BDD SAT algorithm e ciently. Eventually, the results of these subproblems are integrated together that contribute to the solution of the original problem. According to recent industrial assessments, this BDD SAT solver provides solutions to the practical, industrial asynchronous circuit design problem.
DEDICATION GLOBAL SEARCH METHODS FOR SOLVING NONLINEAR OPTIMIZATION PROBLEMS
"... In this thesis, we present new methods for solving nonlinear optimization problems. These problems are di cult to solve because the nonlinear constraints form feasible regions that are di cult to nd, and the nonlinear objectives contain local minima that trap descenttype search methods. In order to ..."
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In this thesis, we present new methods for solving nonlinear optimization problems. These problems are di cult to solve because the nonlinear constraints form feasible regions that are di cult to nd, and the nonlinear objectives contain local minima that trap descenttype search methods. In order to nd good solutions in nonlinear optimization, we focus on the following two key issues: how to handle nonlinear constraints and how to escape from local minima. We use a Lagrangemultiplierbased formulation to handle nonlinear constraints, and develop Lagrangian methods with dynamic control to provide faster and more robust convergence. We extend the traditional Lagrangian theory for the continuous space to the To my wife Lei, my parents, and my son Charles discrete space and develop e cient discrete Lagrangian methods. To overcome local minima, we design a new tracebased globalsearch method that relies on an external traveling trace to pull a search trajectory out of a local optimum in a continuous fashion without having to restart the search from a new starting point. Good starting points identi ed in the global search are used in the local search to identify true local optima. By combining these new methods, we develop a prototype, called Novel (Nonlinear Optimization Via External Lead),