We consider the problem of minimizing a class of quasi-concave functions over a convex set. Quasi-concave functions are generalizations of concave functions and NP-hard to minimize in general. We present a simple full...
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We consider the problem of minimizing a class of quasi-concave functions over a convex set. Quasi-concave functions are generalizations of concave functions and NP-hard to minimize in general. We present a simple fully polynomial time approximation scheme (FPTAS) for minimizing a class of low-rank quasi-concave functions. Our algorithm solves a polynomial number of linear minimization problems and computes an extreme point near-optimal solution. Therefore, it applies directly to combinatorial 0-1 problems where the convex hull of feasible solutions is known. (C) 2013 Elsevier B.V. All rights reserved.
Shop scheduling problems are notorious for their intractability, both in theory and practice. In this paper, we construct a polynomialapproximation scheme for the flow shop scheduling problem with an arbitrary fixed ...
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Shop scheduling problems are notorious for their intractability, both in theory and practice. In this paper, we construct a polynomialapproximation scheme for the flow shop scheduling problem with an arbitrary fixed number of machines. For the three common shop models (open, flow, and job), this result is the only known approximation scheme. Since none of the three models can be approximated arbitrarily closely in the general case (unless P-NP), the result demonstrates the approximability gap between the models in which the number of machines is fixed, and those in which it is part of the input of the instance. The result can be extended to flow shops with job release dates and delivery times and to flow shops with a fixed number of stages, where the number of machines at any stage is fixed. (C) 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
A cutting plane algorithm is presented for finding E-approximate solutions to integer programs contained in the unit hypercube and represented by a separation oracle. Under the assumption that a polynomially bounded b...
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A cutting plane algorithm is presented for finding E-approximate solutions to integer programs contained in the unit hypercube and represented by a separation oracle. Under the assumption that a polynomially bounded ball is contained in the feasible region of the problem, it is demonstrated that the algorithm is an oracle fully polynomial epsilon approximation scheme. Implications of the result for 0/1 integer programming are discussed.
作者:
FISCHETTI, MDEIS
University of Bologna viale Risorgimento 2 40136 Bologna Italy
Given a set of positive integers, the Subset-Sum Problem is to find that subset whose sum is closest to, without exceeding, a given W . For this problem, we present a polynomial-time approximation scheme requiring onl...
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Given a set of positive integers, the Subset-Sum Problem is to find that subset whose sum is closest to, without exceeding, a given W . For this problem, we present a polynomial-time approximation scheme requiring only a linear storage, and prove that its worst-case performance dominates that of the linear-storage approximationschemes from the literature. A modification of the scheme requiring linear time and space for any fixed bound ε on the relative error, is also given. Extensive computational results on randomly generated test problems are reported.
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