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1,428
Hard Formulas For SAT Local Search Algorithms
, 1998
"... In 1992 B. Selman, H. Levesque and D. Mitchell proposed GSAT, a greedy local search algorithm for the Boolean satisfiability problem. Good performance of this algorithm and its modifications has been demonstrated by many experimental results. In 1993 I. P. Gent and T. Walsh proposed CSAT, a version ..."
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of GSAT that almost does not use greediness. It has been recently proved that CSAT can find a satisfying assignment for a restricted class of formulas in the time c n , where c ! 2 is a constant. In this paper we prove a lower bound of the order 2 n for GSAT and CSAT. Namely, we construct formulas F n
On the Hardness of Approximate Reasoning
, 1996
"... Many AI problems, when formalized, reduce to evaluating the probability that a propositional expression is true. In this paper we show that this problem is computationally intractable even in surprisingly restricted cases and even if we settle for an approximation to this probability. We consider va ..."
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Cited by 289 (13 self)
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over a propositional domain. We prove that counting satisfying assignments of propositional languages is intractable even for Horn and monotone formulae, and even when the size of clauses and number of occurrences of the variables are extremely limited. This should be contrasted with the case
Noise strategies for improving local search
 In Proceedings of the Eleventh National Conference on Artificial Intelligence (AAAI94
, 1994
"... It has recently been shown that local search issurprisingly good at nding satisfying assignments for certain computationally hard classes of CNF formulas. The performance of basic local search methods can be further enhanced by introducing mechanisms for escaping from local minima in the search spac ..."
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Cited by 400 (7 self)
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It has recently been shown that local search issurprisingly good at nding satisfying assignments for certain computationally hard classes of CNF formulas. The performance of basic local search methods can be further enhanced by introducing mechanisms for escaping from local minima in the search
Hard and Easy Distributions of SAT Problems
, 1992
"... We report results from largescale experiments in satisfiability testing. As has been observed by others, testing the satisfiability of random formulas often appears surprisingly easy. Here we show that by using the right distribution of instances, and appropriate parameter values, it is possible to ..."
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Cited by 255 (20 self)
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to generate random formulas that are hard, that is, for which satisfiability testing is quite difficult. Our results provide a benchmark for the evaluation of satisfiabilitytesting procedures. Introduction Many computational tasks of interest to AI, to the extent that they can be precisely characterized
Formula
"... July3,1995 Both the quality of the results of TEX's formula layout algorithm and the complexity of its description in the TEXbook [1] are hard to beat. The algorithm is (verbally) described as an imperative program with very complex control ow and complicated manipulations of the data structure ..."
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July3,1995 Both the quality of the results of TEX's formula layout algorithm and the complexity of its description in the TEXbook [1] are hard to beat. The algorithm is (verbally) described as an imperative program with very complex control ow and complicated manipulations of the data
Estimation of effective interresidue contact energies from protein crystal structures: quasichemical approximation
 Macromolecules
, 1985
"... ABSTRACT: Effective interresidue contact energies for proteins in solution are estimated from the numbers of residueresidue contacts observed in crystal structures of globular proteins by means of the quasichemical approximation with an approximate treatment of the effects of chain connectivity. E ..."
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Cited by 269 (11 self)
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, that contact pair formation resembles a chemical reaction, is applied to this system to obtain formulas that relate the statistical averages of the numbers of contacts to the contact energies. The number of effective solvent molecules for each protein is chosen to yield the total number of residue
NP IS AS EASY AS DETECTING UNIQUE SOLUTIONS
, 1986
"... For every known NPcomplete problem, the number of solutions of its instances varies over a large range, from zero to exponentially many. It is therefore natural to ask if the inherent intractability of NPcomplete problems is caused by this wide variation. We give a negative answer to this questi ..."
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Cited by 233 (1 self)
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about the difficulty of specific problems follow. For example, computing the parity of the number of solutions of a SAT formula is shown to be NPhard, and deciding if a SAT formula has a unique solution is shown to be DPhard, under randomized reduction. Central to the study of cryptography
Generating Hard Satisfiability Problems
 Artificial Intelligence
, 1996
"... We report results from largescale experiments in satisfiability testing. As has been observed by others, testing the satisfiability of random formulas often appears surprisingly easy. Here we show that by using the right distribution of instances, and appropriate parameter values, it is possible ..."
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Cited by 108 (2 self)
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, it is possible to generate random formulas that are hard, that is, for which satisfiability testing is quite difficult. Our results provide a benchmark for the evaluation of satisfiabilitytesting procedures. In Artificial Intelligence, 81 (19996) 1729. 1 Introduction Many computational tasks of interest
DomainIndependent Extensions to GSAT: Solving Large Structured Satisfiability Problems
 PROC. IJCAI93
, 1993
"... GSAT is a randomized local search procedure for solving propositional satisfiability problems (Selman et al. 1992). GSAT can 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 proc ..."
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Cited by 227 (10 self)
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GSAT is a randomized local search procedure for solving propositional satisfiability problems (Selman et al. 1992). GSAT can 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 Davis
A backbonesearch heuristic for efficient solving of hard 3SAT formulae
, 2001
"... Of late, new insight into the study of random kSAT formulae has been gained from the introduction of a concept inspired by models of physics, the `backbone ' of a SAT formula which corresponds to the variables having a fixed truth value in all assignments satisfying the maximum number of ..."
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Cited by 77 (1 self)
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Of late, new insight into the study of random kSAT formulae has been gained from the introduction of a concept inspired by models of physics, the `backbone ' of a SAT formula which corresponds to the variables having a fixed truth value in all assignments satisfying the maximum number
Results 1  10
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