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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 62 (1996), S. 539-564 
    ISSN: 1572-9338
    Keywords: Linear programming ; Iri-Imai method ; primal-dual potential function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In this paper, we show that the number of main iterations required by the Iri-Imai algorithm to solve a linear programming problem isO(nL). Moreover, we show that a modification of this algorithm requires only $$\mathcal{O}(\sqrt {nL} )$$ main iterations. In this modification, we measure progress by means of a primal-dual potential function.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 46-47 (1993), S. 203-233 
    ISSN: 1572-9338
    Keywords: Linear programming ; simplex method ; pivot rules ; cycling ; recursion ; minimal index rule ; parametric programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The purpose of this paper is to discuss the various pivot rules of the simplex method and its variants that have been developed in the last two decades, starting from the appearance of the minimal index rule of Bland. We are mainly concerned with finiteness properties of simplex type pivot rules. Well known classical results concerning the simplex method are not considered in this survey, but the connection between the new pivot methods and the classical ones, if there is any, is discussed. In this paper we discuss three classes of recently developed pivot rules for linear programming. The first and largest class is the class of essentially combinatorial pivot rules including minimal index type rules and recursive rules. These rules only use labeling and signs of the variables. The second class contains those pivot rules which can actually be considered as variants or generalizations or specializations of Lemke's method, and so they are closely related to parametric programming. The last class has the common feature that the rules all have close connections to certain interior point methods. Finally, we mention some open problems for future research.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 87 (2000), S. 453-465 
    ISSN: 1436-4646
    Keywords: Key words: quadratic programming – semidefinite programming relaxation – polynomial-time algorithm – approximation ; Mathematics Subject Classification (1991): 90C20, 90C26
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. In this paper we study a class of quadratic maximization problems and their semidefinite programming (SDP) relaxation. For a special subclass of the problems we show that the SDP relaxation provides an exact optimal solution. Another subclass, which is ??-hard, guarantees that the SDP relaxation yields an approximate solution with a worst-case performance ratio of 0.87856.... This is a generalization of the well-known result of Goemans and Williamson for the maximum-cut problem. Finally, we discuss extensions of these results in the presence of a certain type of sign restrictions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 81 (1998), S. 77-87 
    ISSN: 1436-4646
    Keywords: Linear programming ; Interior point method ; Potential function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We propose a polynomial time primal—dual potential reduction algorithm for linear programming. The algorithm generates sequencesd k andv k rather than a primal—dual interior point (x k ,s k ), where $$d_i^k = \sqrt {{{x_i^k } \mathord{\left/ {\vphantom {{x_i^k } {s_i^k }}} \right. \kern-\nulldelimiterspace} {s_i^k }}} $$ and $$v_i^k = \sqrt {x_i^k s_i^k }$$ fori = 1, 2,⋯,n. Only one element ofd k is changed in each iteration, so that the work per iteration is bounded by O(mn) using rank-1 updating techniques. The usual primal—dual iteratesx k ands k are not needed explicitly in the algorithm, whereasd k andv k are iterated so that the interior primal—dual solutions can always be recovered by aforementioned relations between (x k, sk) and (d k, vk) with improving primal—dual potential function values. Moreover, no approximation ofd k is needed in the computation of projection directions. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 82 (1998), S. 235-254 
    ISSN: 1436-4646
    Keywords: Single machine scheduling ; Traveling Salesman Problem ; Polynomial time algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper a one-machine scheduling model is analyzed wheren different jobs are classified intoK groups depending on which additional resource they require. The change-over time from one job to another consists of the removal time or of the set-up time of the two jobs. It is sequence-dependent in the sense that the change-over time is determined by whether or not the two jobs belong to the same group. The objective is to minimize the makespan. This problem can be modeled as an asymmetric Traveling Salesman Problem (TSP) with a specially structured distance matrix. For this problem we give a polynomial time solution algorithm that runs in O(n logn) time. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Computational optimization and applications 13 (1999), S. 87-110 
    ISSN: 1573-2894
    Keywords: convex quadratic system ; existence of optimal solutions ; quadratically constrained quadratic programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we consider optimization problems defined by a quadratic objective function and a finite number of quadratic inequality constraints. Given that the objective function is bounded over the feasible set, we present a comprehensive study of the conditions under which the optimal solution set is nonempty, thus extending the so-called Frank-Wolfe theorem. In particular, we first prove a general continuity result for the solution set defined by a system of convex quadratic inequalities. This result implies immediately that the optimal solution set of the aforementioned problem is nonempty when all the quadratic functions involved are convex. In the absence of the convexity of the objective function, we give examples showing that the optimal solution set may be empty either when there are two or more convex quadratic constraints, or when the Hessian of the objective function has two or more negative eigenvalues. In the case when there exists only one convex quadratic inequality constraint (together with other linear constraints), or when the constraint functions are all convex quadratic and the objective function is quasi-convex (thus allowing one negative eigenvalue in its Hessian matrix), we prove that the optimal solution set is nonempty.
    Type of Medium: Electronic Resource
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