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How to Prove All NP Statements in ZeroKnowledge and a Methodology of Cryptographic Protocol Design (Extended Abstract)
 PROC. OF CRYPTO 1986, THE 6TH ANN. INTL. CRYPTOLOGY CONF., VOLUME 263 OF LECTURE NOTES IN COMPUTER SCIENCE
, 1998
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Flowshop scheduling with limited temporary storage
 Journal of the ACM
, 1980
"... We examine the problem of scheduling 2machine flowshops in order to minimize makespan, using a limited amount of intermediate storage buffers. Although there are efficient algorithms for the extreme cases of zero and infinite buffer capacities, we show that all the intermediate (finite capacity) ca ..."
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We examine the problem of scheduling 2machine flowshops in order to minimize makespan, using a limited amount of intermediate storage buffers. Although there are efficient algorithms for the extreme cases of zero and infinite buffer capacities, we show that all the intermediate (finite capacity) cases are NPcomplete. We prove exact bounds for the relative improvement of execution times when a given buffer capacity is used. We also analyze an efficient heuristic for solving the 1buffer problem, showing that it has a 3/2 worstcase performance. Furthermore, we show that the &quot;nowait &quot; (i.e., zero buffer) flowshop scheduling problem with 4 machines is NPcomplete. This partly settles a wellknown open question, although the 3machine case is left open here. *Research supported by NSF Grant MCS7701192 +Research supported by NSF/RANN grant APR7612036
A Possible World Semantics for Disjunctive Databases
 IEEE Transactions on Data and Knowledge Engineering
, 1999
"... We investigate the fundamental problem of when a ground atom in a disjunctive database is assumed false. There are basically two different approaches for inferring negative information for disjunctive databases; they are Minker's Generalized Closed World Assumption (GCWA) and Ross and Topor&apo ..."
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We investigate the fundamental problem of when a ground atom in a disjunctive database is assumed false. There are basically two different approaches for inferring negative information for disjunctive databases; they are Minker's Generalized Closed World Assumption (GCWA) and Ross and Topor's Disjunctive Database Rule (DDR). A problem with the GCWA is that disjunctive clauses are sometimes interpreted exclusively, even when they are intended for inclusive interpretation. On the other hand, the DDR always interprets disjunctive clauses inclusively. We argue that neither approach is satisfactory. Whether a disjunctive clause is interpreted exclusively or inclusively should be specified explicitly. Negative information should then be inferred according to the stated intent of the disjunctive clauses. A database semantics called PWS is proposed to solve the aforementioned problem. We also show that for propositional databases with no negative clauses, the problem of determining...
Approximating Minimum Subset Feedback Sets in Undirected Graphs with Applications to Multicuts
, 1996
"... Let G = (V; E) be a weighted undirected graph where all weights are at least one. We consider the following generalization of feedback set problems. Let S ae V be a subset of the vertices. A cycle is called interesting if it intersects the set S. A subset feedback edge (vertex) set is a subset of th ..."
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Let G = (V; E) be a weighted undirected graph where all weights are at least one. We consider the following generalization of feedback set problems. Let S ae V be a subset of the vertices. A cycle is called interesting if it intersects the set S. A subset feedback edge (vertex) set is a subset of the edges (vertices) that intersects all interesting cycles. In minimum subset feedback problems the goal is to find such sets of minimumweight. The case in which S consists of a single vertex is equivalent to the multiway cut problem, in which the goal is to separate a given set of terminals. Hence, the subset feedback problem is NPcomplete, and also generalizes the multiway cut problem. We provide a polynomialtime algorithm for approximating the subset feedback edge set problem that achieves an approximation factor of two. For the subset feedback vertex set problem we achieve an approximation factor of minf2\Delta; O(log jSj); O(log ø )g, where \Delta is the maximum degree in G and ø ...
Notes on Levin's Theory of AverageCase Complexity
 Electronic Colloquium on Computational Complexity
, 1997
"... Abstract. In 1984, Leonid Levin initiated a theory of averagecase complexity. We provide an exposition of the basic definitions suggested by Levin, and discuss some of the considerations underlying these definitions. Keywords: Averagecase complexity, reductions. This survey is rooted in the author ..."
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Abstract. In 1984, Leonid Levin initiated a theory of averagecase complexity. We provide an exposition of the basic definitions suggested by Levin, and discuss some of the considerations underlying these definitions. Keywords: Averagecase complexity, reductions. This survey is rooted in the author’s (exposition and exploration) work [4], which was partially reproduded in [1]. An early version of this survey appeared as TR97058 of ECCC. Some of the perspective and conclusions were revised in light of a relatively recent work of Livne [21], but an attempt was made to preserve the spirit of the original survey. The author’s current perspective is better reflected in [7, Sec. 10.2] and [8], which advocate somewhat different definitional choices (e.g., focusing on typical rather than average performace of algorithms). 1
Approximation Algorithms for Submodular Set Cover with Applications
 IEICE Trans. Inf. Syst
, 2000
"... Introduction We start with the set cover( SC ) problem. Given a finite set M and a family N of subsets of M , a subfamily S of N is called a set cover if every element of M appears in some subset in S; in other words, the union of all subsets in S coincides with M . Each set in N is associated w ..."
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Introduction We start with the set cover( SC ) problem. Given a finite set M and a family N of subsets of M , a subfamily S of N is called a set cover if every element of M appears in some subset in S; in other words, the union of all subsets in S coincides with M . Each set in N is associated with a (U"C2T0"'# e) cost, and the cost of a family is the sum of costs of subsets in it. The set cover problem then asks to find a minimum cost set cover. As a special case when all the costs associated with sets are identical, it is called the unit cost set cover, and it is one of the basic NPcomplete optimization problems presented by Karp [17]. he problem is also equivalent to the hitting set problem and the dominating set problem on gra
On the inapproximability of disjoint paths and minimum steiner forest with bandwidth constraints
 Journal of Computer and Systems Sciences
"... In this paper, we study the inapproximability of several wellknown optimization problems in network optimization. We showthat the max directed vertexdisjoint paths problem cannot be approximated within ratio 2 log1& = n unless NP DTIME[2 polylog n], the max directed edgedisjoint paths proble ..."
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Cited by 15 (1 self)
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In this paper, we study the inapproximability of several wellknown optimization problems in network optimization. We showthat the max directed vertexdisjoint paths problem cannot be approximated within ratio 2 log1& = n unless NP DTIME[2 polylog n], the max directed edgedisjoint paths problem cannot be approximated within ratio 2 log1& = n unless NP DTIME [2 polylog n], the integer multicommodity flow problem in directed graphs cannot be approximated within ratio 2 log1& = n unless NP DTIME[2 polylog n], the max undirected vertexdisjoint paths problem does not have a polynomial time approximation scheme unless P=NP, and the minimum Steiner forest with bandwidth constraints problem cannot be approximated within ratio exp ( poly(n)) unless P=NP. 2000 Academic Press 1.
Constructing Cliques Using Restricted Backtracking
, 1996
"... The restricted backtracking algorithmic paradigm is applied to the Maximum Clique Problem. The notion of backtracking coordinates is introduced. The program searches for those cliques whose backtracking coordinates are bounded by the values given in the input. ..."
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Cited by 15 (5 self)
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The restricted backtracking algorithmic paradigm is applied to the Maximum Clique Problem. The notion of backtracking coordinates is introduced. The program searches for those cliques whose backtracking coordinates are bounded by the values given in the input.