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  • Articles  (17,904)
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  • 1
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    Springer
    Mathematical programming 19 (1980), S. 300-312 
    ISSN: 1436-4646
    Keywords: Equilibrium Prices ; Nonconvex Mathematical Programming ; Shadow Prices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper a definition is proposed for the concept of shadow prices in nonconvex programming. For a nonlinear program with equality and inequality constraints, existence of these prices and bounds for their possible values are obtained under the Mangasarian—Fromowitz regularity condition. Their exact values and some continuity properties are obtained under the more restrictive linear independence regularity condition. A definition of equilibrium prices is also proposed. Under convexity assumptions, all definitions and results coincide with those already known on this subject in convex programming.
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  • 2
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    Mathematical programming 19 (1980), S. 313-327 
    ISSN: 1436-4646
    Keywords: Retrogressing Paths ; Homotopy Method ; Fixed-point Algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract For certain functionsf fromR n toR n , the Eaves—Saigal algorithm computes a path inR n × (0, 1] which converges to a zero off. In this case, it is shown that even whenf is of classC ∞ and has a unique zero, the converging path may retrogress infinitely many times.
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  • 3
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    Mathematical programming 21 (1981), S. 190-203 
    ISSN: 1436-4646
    Keywords: Complementarity Problem ; Cones ; Topological Degree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we consider the problem of establishing the number of solutions to the complementarity problem. For the case when the Jacobian of the mapping has all principal minors negative, and satisfies a condition at infinity, we prove that the problem has either 0, 1, 2 or 3 solutions. We also show that when the Jacobian has all principal minors positive, and satisfies a condition at infinity, the problem has a unique solution.
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  • 4
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    Mathematical programming 21 (1981), S. 233-234 
    ISSN: 1436-4646
    Keywords: Polytope ; Subdivision ; Simplex ; Volume ; Centroid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Subdivisions of polytopes are described which place any chosen vertex in a (near-) minimal number of simplices. Ancillary procedures to find volumes and centroids of polytopes are indicated.
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  • 5
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    Mathematical programming 21 (1981), S. 301-318 
    ISSN: 1436-4646
    Keywords: Semi-infinite Programs ; Open Helly-type Theorems ; Finite Subprograms ; Convex Programs ; Multi-criteria Programs ; Quasi-convex Programs ; Quasi-differentiable Programs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We show that a semi-infinite quasi-convex program with certain regularity conditions possesses finitely constrained subprograms with the same optimal value. This result is applied to various problems.
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  • 6
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    Mathematical programming 21 (1981), S. 348-356 
    ISSN: 1436-4646
    Keywords: Multi-extremal Optimization ; Multinomial Distribution ; Bayes Estimate ; Monte Carlo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The solution of ak-extremal problem is defined as the set of pairs (x i * , θi),i = 1, ⋯ ,k, where x t * isi th local minimum andθ i is the volume of the set of attraction of this minimum. A Bayesian estimate ofk and (θ 1 , ⋯ , θ k ) is constructed.
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  • 7
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    Mathematical programming 22 (1982), S. 71-81 
    ISSN: 1436-4646
    Keywords: Blocking ; Antiblocking ; Polarity ; Penumbra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract E. Johnson has recently shown that the concept of a penumbra leads to a simple geometric description of the blocker and antiblocker of a given set. Here we develop some basic results on penumbras which permit us to slightly generalize and simplify results on their relationship to blocking and antiblocking theory. In addition, motivated by the obvious symmetry of our results, we examine the effect of reversing the blocking and antiblocking operations.
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  • 8
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    Mathematical programming 22 (1982), S. 121-121 
    ISSN: 1436-4646
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  • 9
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    Mathematical programming 22 (1982), S. 148-162 
    ISSN: 1436-4646
    Keywords: Set Covering Problem ; Median Problem ; Location Problems ; Heuristics ; Worst Case Analysis ; Continuous Location Problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We describe in this paper polynomial heuristics for three important hard problems—the discrete fixed cost median problem (the plant location problem), the continuous fixed cost median problem in a Euclidean space, and the network fixed cost median problem with convex costs. The heuristics for all the three problems guarantee error ratios no worse than the logarithm of the number of customer points. The derivation of the heuristics is based on the presentation of all types of median problems discussed as a set covering problem.
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  • 10
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    Mathematical programming 22 (1982), S. 227-230 
    ISSN: 1436-4646
    Keywords: Minimax ; Nonconvex Optimization ; Stationary Points
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We give a short proof that in a convex minimax optimization problem ink dimensions there exist a subset ofk + 1 functions such that a solution to the minimax problem with thosek + 1 functions is a solution to the minimax problem with all functions. We show that convexity is necessary, and prove a similar theorem for stationary points when the functions are not necessarily convex but the gradient exists for each function.
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  • 11
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    Mathematical programming 18 (1980), S. 186-196 
    ISSN: 1436-4646
    Keywords: Weber's Problem ; Weiszfeld's Method ; Optimal Location
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract For solving the Euclidean distance Weber problem Weiszfeld proposed an iterative method. This method can also be applied to generalized Weber problems in Banach spaces. Examples for generalized Weber problems are: minimal surfaces with obstacles, Fermat's principle in geometrical optics and brachistochrones with obstacles.
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  • 12
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    Mathematical programming 18 (1980), S. 84-88 
    ISSN: 1436-4646
    Keywords: Complementary Pivot Algorithms ; Triangulations ; Vector Labels ; Borsuk's Theorem on Antipodal Points
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this short note a simple and constructive proof is given for Borsuk's theorem on antipodal points. This is done through a special application of the complementary pivoting algorithm.
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  • 13
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    Mathematical programming 18 (1980), S. 110-110 
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  • 14
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    Mathematical programming 18 (1980), S. 155-168 
    ISSN: 1436-4646
    Keywords: Constrained Optimization ; Differential Equation ; Global Solution ; Nonlinear Programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A new method is presented for finding a local optimum of the equality constrained nonlinear programming problem. A nonlinear autonomous system is introduced as the base of the theory instead of usual approaches. The relation between critical points and local optima of the original optimization problem is proved. Asymptotic stability of the critical points is also proved. A numerical algorithm which is capable of finding local optima systematically at the quadratic rate of convergence is developed from a detailed analysis of the nature of trajectories and critical points. Some numerical results are given to show the efficiency of the method.
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  • 15
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    Mathematical programming 18 (1980), S. 215-227 
    ISSN: 1436-4646
    Keywords: Frank—Wolfe Theorem ; Quadratic Programming ; Norm Coercive Functions ; Polyhedral Sets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The Frank—Wolfe theorem states that a quadratic function, bounded below on a nonempty polyhedral convex set, attains its infimum there. This paper gives sufficient conditions under which a function either attains its infimum on a nonempty polyhedral convex set or is unbounded below on some halfline of that set. Quadratic functions are shown to satisfy these sufficient conditions.
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  • 16
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    Mathematical programming 18 (1980), S. 248-273 
    ISSN: 1436-4646
    Keywords: Legendre Transform ; Stationary Points ; Convex Functions ; Duality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this work non-convex programs are analyzed via Legendre transform. The first part includes definitions and the classification of programs that can be handled by the transformation. It is shown that differentiable functions that are represented as a sum of strictly concave and convex functions belong to this class. Conditions under which a function may have such representation are given. Pseudo duality is defined and the pseudo duality theorem for non linear programs with equality constraints is proved. The techniques described are constructive ones, and they enable tocalculate explicitly a pseudo dual once the primal program is given. Several examples are included. In the convex case these techniques enable the explicit calculation of the dual even in cases where direct calculation was not possible.
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  • 17
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    Mathematical programming 18 (1980), S. 286-290 
    ISSN: 1436-4646
    Keywords: Facility Location ; Steiner's Problem ; Location on the Sphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This note describes the nature of optimal solutions for the spherical Steiner-Weber location problem for the case of unit weights and either 3 or 4 demand points (requireing 4 demand points to lie in an open hemisphere). Geometrically appealing results which are necessary conditions for optimum solutions and spherical analogs of known planar results are obtained.
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  • 18
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    Mathematical programming 24 (1982), S. 257-268 
    ISSN: 1436-4646
    Keywords: Nondifferentiable Programming ; Convex Analysis ; Sensivity Analysis ; Duality Theory ; Second Order Derivative ; Second Order Methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We study differential properties of the support function of the∈-subdifferential of a convex function; applications in algorithmics are also given.
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  • 19
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    Mathematical programming 18 (1980), S. 62-67 
    ISSN: 1436-4646
    Keywords: Economic Interpretation ; Mathematical Programming ; Duality ; Stochastic Programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The purpose of this note is to interpret a class of stochastic programming problems in economic terms. The primal stochastic program is shown to represent a certain production program of an entrepreneur. The dual program, which is also a stochastic program, represents the problem of a contractor who desires to purchase the entrepreneur's resources and sell product back to him.
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  • 20
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    Mathematical programming 21 (1981), S. 120-120 
    ISSN: 1436-4646
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    Topics: Computer Science , Mathematics
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  • 21
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    Mathematical programming 21 (1981), S. 319-330 
    ISSN: 1436-4646
    Keywords: Nonlinear Programming ; Geometric Programming ; Duality Theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The several published methods for mapping a dual solution estimate to a primal solution estimate in posynomial geometric programming provide no criteria for deciding how much deviation from primal feasibility, or discrepancy between the primal and dual objective function values, should be permitted before the primal solution estimate is accepted by the designer. This paper presents a new and simple dual-to-primal conversion method that uses the cost coefficients to provide a sound economic criterion for determining when to accept a primal solution estimate. The primal solution estimate generated is the exact solution to a modified primal obtained from the given primal by modifying the cost coefficients, with the exponent matrix left unchanged. The method is shown to have desirable properties when coupled with a convergent dual algorithm.
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  • 22
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    Mathematical programming 22 (1982), S. 93-103 
    ISSN: 1436-4646
    Keywords: Linear Programming ; Relaxation Method ; Polynomiality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A class of linear programs is given in which the relaxation method for inequalities, under the same operating rules as Khacian's method, is not polynomial in the length of the input. This result holds for any value of the relaxation parameter.
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  • 23
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    Mathematical programming 22 (1982), S. 117-120 
    ISSN: 1436-4646
    Keywords: Augmenting Path Algorithm ; Boolean Lattice ; Jordan-Hölder Theorem ; Matroid Intersection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract It is noted that the decomposition of a network presented by J.C. Picard and M. Queyranne through an algorithmic argument may be defined from a general lattice-theoretic result for more general problems for which the equalities of maximum-flow minimum-cut type hold.
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  • 24
    ISSN: 1436-4646
    Keywords: Geometric Programming ; Code Comparisons ; Numerical Testing ; Nonlinear Programming
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Ten codes or code variants were used to solve the five equivalent posynomial GP problem formulations. Four of these codes were general NLP codes; six were specialized GP codes. A total of forty-two test problems was solved with up to twenty randomly generated starting points per problem. The convex primal formulation is shown to be intrinsically easiest to solve. The general purpose GRG code called OPT appears to be the most efficient code for GP problem solution. The reputed superiority of the specialized GP codes GGP and GPKTC appears to be largely due to the fact that these codes solve the convex primal formulation. The dual approaches are only likely to be competitive for small degree of difficulty, tightly constrained problems.
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  • 25
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    Mathematical programming 22 (1982), S. 231-235 
    ISSN: 1436-4646
    Keywords: Integer Programming ; Covering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract LetA be a non-negative matrix with integer entries and no zero column. The integer round-up property holds forA if for every integral vectorw the optimum objective value of the generalized covering problem min{1y: yA ≥ w, y ≥ 0 integer} is obtained by rounding up to the nearest integer the optimum objective value of the corresponding linear program. A polynomial time algorithm is presented that does the following: given any generalized covering problem with constraint matrixA and right hand side vectorw, the algorithm either finds an optimum solution vector for the covering problem or else it reveals that matrixA does not have the integer round-up property.
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  • 26
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    Mathematical programming 21 (1981), S. 1-18 
    ISSN: 1436-4646
    Keywords: Game Theory ; Cost Allocation ; Spanning Tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We consider the problem of cost allocation among users of a minimum cost spanning tree network. It is formulated as a cooperative game in characteristic function form, referred to as a minimum cost spanning tree (m.c.s.t.) game. We show that the core of a m.c.s.t. game is never empty. In fact, a point in the core can be read directly from any minimum cost spanning tree graph associated with the problem. For m.c.s.t. games with efficient coalition structures we define and construct m.c.s.t. games on the components of the structure. We show that the core and the nucleolus of the original game are the cartesian products of the cores and the nucleoli, respectively, of the induced games on the components of the efficient coalition structure.
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  • 27
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    Mathematical programming 21 (1981), S. 119-119 
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  • 28
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    Mathematical programming 21 (1981), S. 121-136 
    ISSN: 1436-4646
    Keywords: Linear Programming ; Polynomial Algorithms ; Total Unimodularity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This paper describes several algorithms for solution of linear programs. The algorithms are polynomial when the problem data satisfy certain conditions.
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  • 29
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    Mathematical programming 21 (1981), S. 182-189 
    ISSN: 1436-4646
    Keywords: Equilibrium ; Linear Monetary Economy ; Linear Programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract An algorithm is presented for computing equilibria in a linear monetary economy, that is, an exchange economy in which all individuals have linear utility functions and in which goods are bought and sold only in exchange for money. The algorithm computes the equilibrium prices by solving a finite sequence of linear programming problems.
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    Mathematical programming 21 (1981), S. 229-232 
    ISSN: 1436-4646
    Keywords: Primal Feasible Basis ; Dual Feasible Basis ; Basic Variable ; Nonbasic Variable ; Optimal Basic Solution
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In a recent paper M.C. Cheng proposed new criteria for the simplex algorithm which guarantee that (i) a nonbasic variable of a basic feasible solution will remain nonbasic in an optimal basic solution, (ii) a basic variable of a basic solution will remain basic in an optimal basic solution. This comment gives (i) a slight generalization of the first result and (ii) a counterexample to the second proposition.
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    Mathematical programming 21 (1981), S. 240-240 
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  • 32
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    Mathematical programming 21 (1981), S. 241-261 
    ISSN: 1436-4646
    Keywords: Dual problem ; Duality Theory ; Optimality Conditions ; Price Functions ; Nonlinear Programming ; Integer Programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We survey some recent developments in duality theory with the idea of explaining and unifying certain basic duality results in both nonlinear and integer programming. The idea of replacing dual variables (prices) by price functions, suggested by Everett and developed by Gould, is coupled with an appropriate dual problem with the consequence that many of the results resemble those used in linear programming. The dual problem adopted has a (traditional) economic interpretation and dual feasibility then provides a simple alternative to concepts such as conjugate functions or subdifferentials used in the study of optimality. In addition we attempt to make precise the relationship between primal, dual and saddlepoint results in both the traditional Lagrangean and the more general duality theories and to see the implications of passing from prices to price functions. Finally, and perhaps surprisingly, it appears that all the standard algorithms terminate by constructing primal and dual feasible solutions of equal value, i.e., by satisfying generalised optimality conditions.
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    Mathematical programming 21 (1981), S. 358-358 
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    Mathematical programming 22 (1982), S. 12-38 
    ISSN: 1436-4646
    Keywords: Graph ; Matching ; Branching ; Linear Programming ; Polyhedron
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Matching forests generalize branchings in a directed graph and matchings in an undirected graph. We present an efficient algorithm, the PMF Algorithm, for the problem: given a mixed graphG and a real weight on each of its edges, find a perfect matching forest of maximum weight-sum. The PMF Algorithm proves the sufficiency of a linear system which definesP = (G) andP(G), the convex hull of incidence vectors of perfect matching forests and matching forests respectively ofG. The algorithm also provides a generalization of Tutte's theorem on the existence of perfect matchings in an undirected graph.
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    Mathematical programming 22 (1982), S. 122-123 
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    Mathematical programming 22 (1982), S. 141-147 
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    Keywords: Integer Rounding ; Pluperfect Graphs ; Combinatorial Optimization
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    Notes: Abstract LetA be a nonnegative integral matrix with no zero columns. Theinteger round-up property holds forA if for each nonnegative integral vectorw, the solution value to the integer programming problem min{1 ⋅y: yA ≥ w, y ≥ 0, y integer} is obtained by rounding up to the nearest integer the solution value to the corresponding linear programming problem min{1 ⋅y: yA ≥ w, y ≥ 0}. Theinteger round-down property is similarly defined for a nonnegative integral matrixB with no zero rows by considering max{1 ⋅y: yB ≤ w, y ≥ 0, y integer} and its linear programming correspondent. It is shown that the integer round-up and round-down properties can be checked through a finite process. The method of proof motivates a new and elementary proof of Fulkerson's Pluperfect Graph Theorem.
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    Mathematical programming 22 (1982), S. 236-237 
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    Mathematical programming 22 (1982), S. 304-315 
    ISSN: 1436-4646
    Keywords: Location Theory ; Tree Networks ; Rigid Circuit Graphs ; Polynomial Algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We discuss several forms of thep-center location problems on an undirected tree network. Our approach is based on utilizing results for rigid circuit graphs to obtain polynomial algorithms for solving the model. Duality theory on perfect graphs is used to define and solve the dual location model.
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    Mathematical programming 23 (1982), S. 111-116 
    ISSN: 1436-4646
    Keywords: Multicriteria Optimization ; Convex Analysis
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    Notes: Abstract Existence and characterization theorems for the efficient (nondominated) set of decisions inR n are presented. The existence is proved when the set of decisions satisfies some compactness conditions. The efficient set is characterized in terms of the exposed efficient decisions when certain convexity and compactness conditions are satisfied.
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    Mathematical programming 23 (1982), S. 170-180 
    ISSN: 1436-4646
    Keywords: Set Covering ; Heuristic Algorithms ; Worst Case Analysis ; Bounds
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In [2], Chvatal provided the tight worst case bound of the set covering greedy heuristic. We considered a general class of greedy type set covering heuristics. Their worst case bounds are dominated by that of the greedy heuristic.
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    Mathematical programming 23 (1982), S. 216-226 
    ISSN: 1436-4646
    Keywords: Nonsmooth Optimization ; Subgradient ; Subdifferential ; Bundle Type Method ; Deletion Rule ; Resetting
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A numerical method for the unconstrained minimization of a convex nonsmooth function of several variables is presented. It is closely related to the ‘bundle type’ approach and to the conjugate subgradient method. A way is suggested to reduce the amount of information to be stored during the computational procedure. Global convergence of the method to the minimum is proved.
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    Mathematical programming 23 (1982), S. 326-340 
    ISSN: 1436-4646
    Keywords: Optimization ; Quasi-Newton ; Conjugate Gradient
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    Notes: Abstract In this paper we study conjugate gradient algorithms for large optimization problems. These methods accelerate (or precondition) the conjugate gradient method by means of quasi-Newton matrices, and are designed to utilize a variable amount of storage, depending on how much information is retained in the quasi-Newton matrices. We are concerned with the behaviour of such methods on the underlying quadratic model, and in particular, with finite termination properties.
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    Mathematical programming 23 (1982), S. 357-360 
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    Mathematical programming 18 (1980), S. 138-145 
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    Keywords: Set-covering Problem ; Branch and Bound ; Lower Bounds ; Steiner Triple Systems
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    Notes: Abstract Fulkerson et al. have given two examples of set covering problems that are empirically difficult to solve. They arise from Steiner triple systems and the larger problem, which has a constraint matrix of size 330 × 45 has only recently been solved. In this note, we show that the Steiner triple systems do indeed give rise to a series of problems that are probably hard to solve by implicit enumeration. The main result is that for ann variable problem, branch and bound algorithms using a linear programming relaxation, and/or elimination by dominance require the examination of a super-polynomial number of partial solutions
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    Mathematical programming 18 (1980), S. 228-228 
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    Mathematical programming 18 (1980), S. 232-232 
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    Mathematical programming 18 (1980), S. 308-329 
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    Keywords: Polytopes ; Linear Programming
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    Notes: Abstract This paper provides answers to several questions raised by V. Klee regarding the efficacy of Mattheiss' algorithm for finding all vertices of convex polytopes. Several results relating to the expected properties of polytopes are given which indicate thatn-polytopes defined by “large” numbers of constraints are difficult to obtain by random processes, the expected value of the number of vertices of polytope is considerably less than Klee's least upper bound the expected performance of Mattheiss' algorithm is far better than Klee's upper bound would suggest.
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    Mathematical programming 68 (1995), S. 105-130 
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    Keywords: primary 49B34 ; secondary 90C31 ; 93C30 ; Variational inequalities ; Sensitivity analysis ; Generalized Jacobian
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    Notes: Abstract Optimization problems with variational inequality constraints are converted to constrained minimization of a local Lipschitz function. To this minimization a non-differentiable optimization method is used; the required subgradients of the objective are computed by means of a special adjoint equation. Besides tests with some academic examples, the approach is applied to the computation of the Stackelberg—Cournot—Nash equilibria and to the numerical solution of a class of quasi-variational inequalities.
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    Mathematical programming 69 (1995), S. 1-43 
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    Keywords: Mathematical programming ; Cutting planes ; Analytic center
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    Notes: Abstract Anoracle for a convex setS ⊂ ℝ n accepts as input any pointz in ℝ n , and ifz ∈S, then it returns ‘yes’, while ifz ∉S, then it returns ‘no’ along with a separating hyperplane. We give a new algorithm that finds a feasible point inS in cases where an oracle is available. Our algorithm uses the analytic center of a polytope as test point, and successively modifies the polytope with the separating hyperplanes returned by the oracle. The key to establishing convergence is that hyperplanes judged to be ‘unimportant’ are pruned from the polytope. If a ball of radius 2−L is contained inS, andS is contained in a cube of side 2 L+1, then we can show our algorithm converges after O(nL 2) iterations and performs a total of O(n 4 L 3+TnL 2) arithmetic operations, whereT is the number of arithmetic operations required for a call to the oracle. The bound is independent of the number of hyperplanes generated in the algorithm. An important application in which an oracle is available is minimizing a convex function overS.
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    Mathematical programming 69 (1995), S. 45-73 
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    Keywords: Cutting plane ; Stochastic programming ; Analytic center ; Interior-point method
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    Notes: Abstract The stochastic linear programming problem with recourse has a dual block-angular structure. It can thus be handled by Benders' decomposition or by Kelley's method of cutting planes; equivalently the dual problem has a primal block-angular structure and can be handled by Dantzig-Wolfe decomposition—the two approaches are in fact identical by duality. Here we shall investigate the use of the method of cutting planes from analytic centers applied to similar formulations. The only significant difference form the aforementioned methods is that new cutting planes (or columns, by duality) will be generated not from the optimum of the linear programming relaxation, but from the analytic center of the set of localization.
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    Mathematical programming 69 (1995), S. 237-253 
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    Keywords: Variational inequality ; Nonlinear complementarity ; Nonlinear programming ; Continuation method
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    Notes: Abstract This paper presents a continuation method for monotone variational inequality problems based on a new smooth equation formulation. The existence, uniqueness and limiting behavior of the path generated by the method are analyzed.
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    Mathematical programming 69 (1995), S. 269-309 
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    Keywords: Quadratic programming ; Submodular constraints ; Kuhn-Tucker conditions ; Lexicographically optimal flow ; Parametric maximum flow
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    Notes: Abstract We present new strongly polynomial algorithms for special cases of convex separable quadratic minimization over submodular constraints. The main results are: an O(NM log(N 2/M)) algorithm for the problemNetwork defined on a network onM arcs andN nodes; an O(n logn) algorithm for thetree problem onn variables; an O(n logn) algorithm for theNested problem, and a linear time algorithm for theGeneralized Upper Bound problem. These algorithms are the best known so far for these problems. The status of the general problem and open questions are presented as well.
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    Mathematical programming 69 (1995), S. 335-349 
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    Keywords: Polyhedral combinatorics ; Valid inequalities ; Travelling salesman ; Worst-case analysis
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    Notes: Abstract We consider most of the known classes of valid inequalities for the graphical travelling salesman polyhedron and compute the worst-case improvement resulting from their addition to the subtour polyhedron. For example, we show that the comb inequalities cannot improve the subtour bound by a factor greater than 10/9. The corresponding factor for the class of clique tree inequalities is 8/7, while it is 4/3 for the path configuration inequalities.
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    Mathematical programming 70 (1995), S. 1-16 
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    Keywords: Stochastic programming ; Polyhedral functions ; Simplicial functions
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    Notes: Abstract A dual method is presented to solve a linearly constrained optimization problem with convex, polyhedral objective function, along with a fast bounding technique, for the optimum value. The method can be used to solve problems, obtained from LPs, where some of the constraints are not required to be exactly satisfied but are penalized by piecewise linear functions, which are added to the objective function of the original problem. The method generalizes an earlier solution technique developed by Prékopa (1990). Applications to stochastic programming are also presented.
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    Mathematical programming 70 (1995), S. 107-122 
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    Keywords: Linear complementarity problem ; Predictor—corrector algorithm ; Complexity analysis ; Central trajectory ; Curvature integral ; Interior-point methods
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    Notes: Abstract In this paper, we propose a predictor—corrector-type algorithm for solving the linear complementarity problem (LCP), and prove that the actual number of iterations needed by the algorithm is bounded from above and from below by a curvature integral along the central trajectory of the problem. This curvature integral is not greater than, and possibly smaller than, the best upper bound obtained in the literature to date.
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    Mathematical programming 70 (1995), S. 159-172 
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    Keywords: Parametric nonlinear programming ; Directional differentiability ; B-derivative ; Piecewise smooth function ; Nonunique multipliers ; Degeneracy
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    Notes: Abstract Consider a parametric nonlinear optimization problem subject to equality and inequality constraints. Conditions under which a locally optimal solution exists and depends in a continuous way on the parameter are well known. We show, under the additional assumption of constant rank of the active constraint gradients, that the optimal solution is actually piecewise smooth, hence B-differentiable. We show, for the first time to our knowledge, a practical application of quadratic programming to calculate the directional derivative in the case when the optimal multipliers are not unique.
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    Mathematical programming 70 (1995), S. 191-200 
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    Keywords: Strictly pseudomonotone map ; Z-map ; Complementarity problem ; Least element problem
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    Notes: Abstract Strictly pseudomonotoneZ-maps operating on Banach lattices are considered. Equivalence of complementarity problems and least-element problems is established under certain regularity and growth conditions. This extends a recent result by Riddell (1981) for strictly monotoneZ-maps to the pseudomonotone case. Some other problems equivalent to the above are discussed as well.
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    Mathematical programming 70 (1995), S. 251-277 
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    Keywords: Linear programming ; Barrier methods ; Interior-point methods
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    Notes: Abstract Many interior-point methods for linear programming are based on the properties of the logarithmic barrier function. After a preliminary discussion of the convergence of the (primal) projected Newton barrier method, three types of barrier method are analyzed. These methods may be categorized as primal, dual and primal—dual, and may be derived from the application of Newton's method to different variants of the same system of nonlinear equations. A fourth variant of the same equations leads to a new primal—dual method. In each of the methods discussed, convergence is demonstrated without the need for a nondegeneracy assumption or a transformation that makes the provision of a feasible point trivial. In particular, convergence is established for a primal—dual algorithm that allows a different step in the primal and dual variables and does not require primal and dual feasibility. Finally, a new method for treating free variables is proposed.
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    Keywords: Linear programming ; Mixed-integer programming ; Large-scale optimization ; Airline fleet assignment
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    Notes: Abstract Given a flight schedule and set of aircraft, the fleet assignment problem is to determine which type of aircraft should fly each flight segment. This paper describes a basic daily, domestic fleet assignment problem and then presents chronologically the steps taken to solve it efficiently. Our model of the fleet assignment problem is a large multi-commodity flow problem with side constraints defined on a time-expanded network. These problems are often severely degenerate, which leads to poor performance of standard linear programming techniques. Also, the large number of integer variables can make finding optimal integer solutions difficult and time-consuming. The methods used to attack this problem include an interior-point algorithm, dual steepest edge simplex, cost perturbation, model aggregation, branching on set-partitioning constraints and prioritizing the order of branching. The computational results show that the algorithm finds solutions with a maximum optimality gap of 0.02% and is more than two orders of magnitude faster than using default options of a standard LP-based branch-and-bound code.
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    Mathematical programming 71 (1995), S. 77-100 
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    Keywords: Convex linearly constrained problems ; Variational inequalities ; Interior methods ; Entropy-like proximal method ; Maximal monotone operator
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    Notes: Abstract In this paper, an entropy-like proximal method for the minimization of a convex function subject to positivity constraints is extended to an interior algorithm in two directions. First, to general linearly constrained convex minimization problems and second, to variational inequalities on polyhedra. For linear programming, numerical results are presented and quadratic convergence is established.
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    Mathematical programming 71 (1995), S. 29-50 
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    Keywords: Max-cut ; Cut polytope ; Metric polytope ; Linear relaxation ; One-third-integrality ; Box one-third-integrality ; Forbidden minor
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    Notes: Abstract Given a graphG = (V, E), the metric polytopeS (G) is defined by the inequalitiesx(F) − x(C∖F) ⩽ |F| − 1 for $$F \subseteq C$$ , |F| odd,C cycle ofG, and 0 ⩽x e ⩽ 1 fore ∈ E. Optimization overS (G) provides an approximation for the max-cut problem. The graphG is called 1/d-integral if all the vertices ofS(G) have their coordinates in{i/d ∣ 0 ⩽ i ⩽ d}. We prove that the class of 1/d-integral graphs is closed under minors, and we present several minimal forbidden minors for 1/3-integrality. In particular, we characterize the 1/3-integral graphs on seven nodes. We study several operations preserving 1/d-integrality, in particular, thek-sum operation for 0 ⩽k ⩽ 3. We prove that series parallel graphs are characterized by the following stronger property. All vertices of the polytopeS (G) ∩ {x ∣ ℓ ⩽ x ⩽ u} are 1/3-integral for every choice of 1/3-integral boundsℓ, u on the edges ofG.
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    Mathematical programming 71 (1995), S. 101-112 
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    Keywords: Minmax ; Maximal covering problems ; Multi criteria decision-making
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    Notes: Abstract In this paper we introduce the parametric minquantile problem, a weighted generalisation ofkth maximum minimisation. It is shown that, under suitable quasiconvexity assumptions, its resolution can be reduced to solving a polynomial number of minmax problems. It is also shown how this simultaneously solves (parametric) maximal covering problems. It follows that bicriteria problems, where the aim is to both maximize the covering and minimize the cover-level, are reducible to a discrete problem, on which any multiple criteria method may be applied.
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    Mathematical programming 71 (1995), S. 71-76 
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    Keywords: Location theory ; Fermat—Weber problem ; Weiszfeld's iterative algorithm
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    Notes: Abstract The Fermat—Weber location problem requires finding a point in ℝ N that minimizes the sum of weighted Euclidean distances tom given points. A one-point iterative method was first introduced by Weiszfeld in 1937 to solve this problem. Since then several research articles have been published on the method and generalizations thereof. Global convergence of Weiszfeld's algorithm was proven in a seminal paper by Kuhn in 1973. However, since them given points are singular points of the iteration functions, convergence is conditional on none of the iterates coinciding with one of the given points. In addressing this problem, Kuhn concluded that whenever them given points are not collinear, Weiszfeld's algorithm will converge to the unique optimal solution except for a denumerable set of starting points. As late as 1989, Chandrasekaran and Tamir demonstrated with counter-examples that convergence may not occur for continuous sets of starting points when the given points are contained in an affine subspace of ℝ N . We resolve this open question by proving that Weiszfeld's algorithm converges to the unique optimal solution for all but a denumerable set of starting points if, and only if, the convex hull of the given points is of dimensionN.
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    Mathematical programming 71 (1995), S. 153-177 
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    Keywords: Network optimization ; Assignment problem ; Algorithms ; Experimental evaluation ; Cost scaling
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    Notes: Abstract The cost scaling push-relabel method has been shown to be efficient for solving minimum-cost flow problems. In this paper we apply the method to the assignment problem and investigate implementations of the method that take advantage of assignment's special structure. The results show that the method is very promising for practical use.
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    Mathematical programming 71 (1995), S. 195-206 
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    Keywords: Superfluous matrix ; Linear complementarity problem
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    Notes: Abstract Superfluous matrices were introduced by Howe (1983) in linear complementarity. In general, producing examples of this class is tedious (a few examples can be found in Chapter 6 of Cottle, Pang and Stone (1992)). To overcome this problem, we define a new class of matrices $$\bar Z$$ and establish that in $$\bar Z$$ superfluous matrices of any ordern ⩾ 4 can easily be constructed. For every integerk, an example of a superfluous matrix of degreek is exhibited in the end.
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    Mathematical programming 71 (1995), S. 249-258 
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    Keywords: Combinatorial optimization ; Integrality of polyhedra ; Generalized set packing ; Covering
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    Notes: Abstract A 0, ±1-matrixA is balanced if, in every submatrix with two nonzero entries per row and column, the sum of the entries is a multiple of four. This definition was introduced by Truemper (1978) and generalizes the notion of a balanced 0, 1-matrix introduced by Berge (1970). In this paper, we extend a bicoloring theorem of Berge (1970) and total dual integrality results of Fulkerson, Hoffman and Oppenheim (1974) to balanced 0, ±1-matrices.
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    Mathematical programming 71 (1995), S. 369-370 
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    Keywords: Local Lipschitz property ; Infinite-dimensional Hilbert space
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    Notes: Abstract An oversight in a paper of Correa and Lemaréchal (this journal, 1993) is noted; a counterexample is given.
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    Mathematical programming 80 (1998), S. 17-33 
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    Keywords: Dual simplex method ; Maximum flow ; Strongly polynomial ; Preflow algorithm ; Valid distance labels
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    Notes: Abstract This paper presents dual network simplex algorithms that require at most 2nm pivots and O(n 2 m) time for solving a maximum flow problem on a network ofn nodes andm arcs. Refined implementations of these algorithms and a related simplex variant that is not strictly speaking a dual simplex algorithm are shown to have a complexity of O(n 3). The algorithms are based on the concept of apreflow and depend upon the use of node labels that are underestimates of the distances from the nodes to the sink node in the extended residual graph associated with the current flow. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 80 (1998), S. 35-61 
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    Keywords: Graph partitioning ; Linear programming ; Bundle method ; Parallel optimization
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    Notes: Abstract This paper describes heuristics for partitioning a generalM × N matrix into arrowhead form. Such heuristics are useful for decomposing large, constrained, optimization problems into forms that are amenable to parallel processing. The heuristics presented can be easily implemented using publicly available graph partitioning algorithms. The application of such techniques for solving large linear programs is described. Extensive computational results on the effectiveness of our partitioning procedures and their usefulness for parallel optimization are presented. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 80 (1998), S. 129-160 
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    Keywords: Semidefinite programming ; Infeasible-interior-point method ; Predictor—correctormethod ; Superlinear convergence ; Primal—dual nondegeneracy
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    Notes: Abstract An example of an SDP (semidefinite program) exhibits a substantial difficulty in proving the superlinear convergence of a direct extension of the Mizuno—Todd—Ye type predictor—corrector primal-dual interior-point method for LPs (linear programs) to SDPs, and suggests that we need to force the generated sequence to converge to a solution tangentially to the central path (or trajectory). A Mizuno—Todd—Ye type predictor—corrector infeasible-interior-point algorithm incorporating this additional restriction for monotone SDLCPs (semidefinite linear complementarity problems) enjoys superlinear convergence under strict complementarity and nondegeneracy conditions. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 80 (1998), S. 161-169 
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    Keywords: Variational inequalities ; Complementarity problems ; Walrasian equilibrium ; Computational general equilibrium
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    Notes: Abstract This paper explains a method by which the number of variables in a variational inequality having a certain form can be substantially reduced by changing the set over which the variational inequality is posed. The method applies in particular to certain economic equilibrium problems occurring in applications. We explain and justify the method, and give examples of its application, including a numerical example in which the solution time for the reduced problem was approximately 2% of that for the problem in its original form. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 81 (1998), S. 201-214 
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    Keywords: Integer programming ; Cutting planes ; Cover inequalities ; Lifting ; Gomory mixed integer cuts ; Cut-and-branch
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    Notes: Abstract We investigate the use of cutting planes for integer programs with general integer variables. We show how cutting planes arising from knapsack inequalities can be generated and lifted as in the case of 0–1 variables. We also explore the use of Gomory's mixed-integer cuts. We address both theoretical and computational issues and show how to embed these cutting planes in a branch-and-bound framework. We compare results obtained by using our cut generation routines in two existing systems with a commercially available branch-and-bound code on a range of test problems arising from practical applications. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 81 (1998), S. 229-256 
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    Keywords: Branch-and-cut algorithm ; Clustering ; Compiler design ; Equipartitioning ; Finite element method ; Graph partitioning ; Layout of electronic circuits ; Separation heuristics
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    Notes: Abstract In this paper we consider the problem ofk-partitioning the nodes of a graph with capacity restrictions on the sum of the node weights in each subset of the partition, and the objective of minimizing the sum of the costs of the edges between the subsets of the partition. Based on a study of valid inequalities, we present a variety of separation heuristics for cycle, cycle with ears, knapsack tree and path-block cycle inequalities among others. The separation heuristics, plus primal heuristics, have been implemented in a branch-and-cut routine using a formulation including variables for the edges with nonzero costs and node partition variables. Results are presented for three classes of problems: equipartitioning problems arising in finite element methods and partitioning problems associated with electronic circuit layout and compiler design. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 81 (1998), S. 327-347 
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    Keywords: Convex composite function ; Second-order global optimality ; Second-order duality ; Variational inequality
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    Notes: Abstract In recent years second-order sufficient conditions of an isolated local minimizer for convex composite optimization problems have been established. In this paper, second-order optimality conditions are obtained of aglobal minimizer for convex composite problems with a non-finite valued convex function and a twice strictly differentiable function by introducing a generalized representation condition. This result is applied to a minimization problem with a closed convex set constraint which is shown to satisfy the basic constraint qualification. In particular, second-order necessary and sufficient conditions of a solution for a variational inequality problem with convex composite inequality constraints are obtained. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 82 (1998), S. 1-1 
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    Mathematical programming 82 (1998), S. 3-12 
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    Keywords: Symmetric submodular function minimization ; Submodular function minimization ; Symmetric submodular functions ; Submodular functions ; Submodular systems
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    Notes: Abstract We describe a purely combinatorial algorithm which, given a submodular set functionf on a finite setV, finds a nontrivial subsetA ofV minimizingf[A] + f[V ∖ A]. This algorithm, an extension of the Nagamochi—Ibaraki minimum cut algorithm as simplified by Stoer and Wagner [M. Stoer, F. Wagner, A simple min cut algorithm, Proceedings of the European Symposium on Algorithms ESA '94, LNCS 855, Springer, Berlin, 1994, pp. 141–147] and by Frank [A. Frank, On the edge-connectivity algorithm of Nagamochi and Ibaraki, Laboratoire Artémis, IMAG, Université J. Fourier, Grenbole, 1994], minimizes any symmetric submodular function using O(|V|3) calls to a function value oracle. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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    Mathematical programming 82 (1998), S. 41-81 
    ISSN: 1436-4646
    Keywords: Random sampling ; Greedy algorithm ; Matroid basis ; Matroid partitioning
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    Notes: Abstract Random sampling is a powerful tool for gathering information about a group by considering only a small part of it. We discuss some broadly applicable paradigms for using random sampling in combinatorial optimization, and demonstrate the effectiveness of these paradigms for two optimization problems on matroids: finding an optimum matroid basis and packing disjoint matroid bases. Application of these ideas to the graphic matroid led to fast algorithms for minimum spanning trees and minimum cuts. An optimum matroid basis is typically found by agreedy algorithm that grows an independent set into an optimum basis one element at a time. This continuous change in the independent set can make it hard to perform the independence tests needed by the greedy algorithm. We simplify matters by using sampling to reduce the problem of finding an optimum matroid basis to the problem of verifying that a givenfixed basis is optimum, showing that the two problems can be solved in roughly the same time. Another application of sampling is to packing matroid bases, also known as matroid partitioning. Sampling reduces the number of bases that must be packed. We combine sampling with a greedy packing strategy that reduces the size of the matroid. Together, these techniques give accelerated packing algorithms. We give particular attention to the problem of packing spanning trees in graphs, which has applications in network reliability analysis. Our results can be seen as generalizing certain results from random graph theory. The techniques have also been effective for other packing problems. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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  • 78
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    Keywords: Quadratic assignment ; Special cases ; Polynomially solvable ; Anti-Monge matrices ; Toeplitz matrices
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    Notes: Abstract This paper investigates a restricted version of the Quadratic Assignment Problem (QAP), where one of the coefficient matrices is an Anti-Monge matrix with non-decreasing rows and columns and the other coefficient matrix is a symmetric Toeplitz matrix. This restricted version is called the Anti-Monge—Toeplitz QAP. There are three well-known combinatorial problems that can be modeled via the Anti-Monge—Toeplitz QAP: (Pl) The “Turbine Problem”, i.e. the assignment of given masses to the vertices of a regular polygon such that the distance of the center of gravity of the resulting system to the center of the polygon is minimized. (P2) The Traveling Salesman Problem on symmetric Monge distance matrices. (P3) The arrangement of data records with given access probabilities in a linear storage medium in order to minimize the average access time. We identify conditions on the Toeplitz matrixB that lead to a simple solution for the Anti-Monge—Toeplitz QAP: The optimal permutation can be given in advance without regarding the numerical values of the data. The resulting theorems generalize and unify several known results on problems (P1), (P2), and (P3). We also show that the Turbine Problem is NP-hard and consequently, that the Anti-Monge—Toeplitz QAP is NP-hard in general. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.
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  • 79
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    Mathematical programming 85 (1999), S. 135-156 
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    Keywords: Key words: bound constrained quadratic programming – Huber’s M–estimator – condition estimation – Newton iteration – factorization update
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    Notes: 1 , the smallest eigenvalue of a symmetric, positive definite matrix, and is solved by Newton iteration with line search. The paper describes the algorithm and its implementation including estimation of λ1, how to get a good starting point for the iteration, and up- and downdating of Cholesky factorization. Results of extensive testing and comparison with other methods for constrained QP are given.
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    Mathematical programming 85 (1999), S. 35-49 
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    Keywords: Key words: bimatrix game – quasi-strict equilibrium ; Mathematics Subject Classification (1991): 90D05
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    Mathematical programming 85 (1999), S. 107-134 
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    Keywords: Key words: equilibrium constraints – variational inequality problems – strong monotonicity – optimality conditions – global convergence ; Mathematics Subject Classification (1991): 90C30, 90C33, 65K05
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    Mathematical programming 85 (1999), S. 363-377 
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    Notes: 1 ,...,Am are true, then at least ℓ of the propositions B1,...,Bn are true. The main result of the paper is that the procedure in fact provides a convex hull description.
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  • 83
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    Keywords: Key words: maximum-entropy sampling – branch and bound – nonlinear programming
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  • 84
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    Mathematical programming 85 (1999), S. 259-276 
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    Keywords: Key words: linear complementary problems – Q-matrices – polyhedral combinatorics – triangulations of point configurations – 0-1 polytopes
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    Notes: T (Mx+q)=0, Mx+q≥0, x≥0 has a solution. We explain how one can use the polyhedral structure of the set of all triangulations of a finite point set to determine if an n×n matrix M is a Q-matrix. Our implementation of the algorithm is practical for deciding the Q-nature for all M with n≤8.
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  • 85
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    Mathematical programming 85 (1999), S. 593-616 
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    Keywords: Key words: concave optimization – conical algorithms –ω-subdivisions Mathematics Subject Classification (1991): 90C26, 65K05
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    Notes: Abstract. In this paper the problem of finding the global optimum of a concave function over a polytope is considered. A well-known class of algorithms for this problem is the class of conical algorithms. In particular, the conical algorithm based on the so called ω-subdivision strategy is considered. It is proved that, for any given accuracy ε〉0, this algorithm stops in a finite time by returning an ε-optimal solution for the problem, while it is convergent for ε=0.
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    Mathematical programming 85 (1999), S. 439-467 
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    Keywords: Mathematics Subject Classification (1991): 90C11
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    Notes: Abstract. We investigate strong inequalities for mixed 0-1 integer programs derived from flow cover inequalities. Flow cover inequalities are usually not facet defining and need to be lifted to obtain stronger inequalities. However, because of the sequential nature of the standard lifting techniques and the complexity of the optimization problems that have to be solved to obtain lifting coefficients, lifting of flow cover inequalities is computationally very demanding. We present a computationally efficient way to lift flow cover inequalities based on sequence independent lifting techniques and give computational results that show the effectiveness of our lifting procedures.
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  • 87
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    Mathematical programming 85 (1999), S. 525-540 
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    Keywords: Key words: semidefinite programming – perturbation theory – Kantorovi theory – condition number Mathematics Subject Classification (1991): 90C31, 90C25, 90C05
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    Notes: theory. This approach also quantifies the size of permissible perturbations. We include a discussion of these results for block diagonal semidefinite programs, of which linear programming is a special case.
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    Mathematical programming 86 (1999), S. 219-223 
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    Keywords: Key words: linear programming – computational complexity – complexity measure Mathematics Subject Classification (1991): 90C05, 90C60, 68Q25
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    Notes: Abstract. Given an m×n integer matrix A of full row rank, we consider the problem of computing the maximum of ∥B -1 A∥2 where B varies over all bases of A. This quantity appears in various places in the mathematical programming literature. More recently, logarithm of this number was the determining factor in the complexity bound of Vavasis and Ye’s primal-dual interior-point algorithm. We prove that the problem of approximating this maximum norm, even within an exponential (in the dimension of A) factor, is NP-hard. Our proof is based on a closely related result of L. Khachiyan [1].
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  • 89
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    Keywords: Key words: non-interior point method – complementarity problem – smoothing function – homotopy method
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    Notes: Abstract. We propose a class of non-interior point algorithms for solving the complementarity problems(CP): Find a nonnegative pair (x,y)∈ℝ 2n satisfying y=f(x) and x i y i =0 for every i∈{1,2,...,n}, where f is a continuous mapping from ℝ n to ℝ n . The algorithms are based on the Chen-Harker-Kanzow-Smale smoothing functions for the CP, and have the following features; (a) it traces a trajectory in ℝ 3n which consists of solutions of a family of systems of equations with a parameter, (b) it can be started from an arbitrary (not necessarily positive) point in ℝ 2n in contrast to most of interior-point methods, and (c) its global convergence is ensured for a class of problems including (not strongly) monotone complementarity problems having a feasible interior point. To construct the algorithms, we give a homotopy and show the existence of a trajectory leading to a solution under a relatively mild condition, and propose a class of algorithms involving suitable neighborhoods of the trajectory. We also give a sufficient condition on the neighborhoods for global convergence and two examples satisfying it.
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    Mathematical programming 86 (1999), S. 41-50 
    ISSN: 1436-4646
    Keywords: Key words: resolvent method – proximal point method – bundle method – bundle-trust region method – subgradient Mathematics Subject Classification (1991): 90C25, 49M45
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    Notes: Abstract. This paper establishes a linear convergence rate for a class of epsilon-subgradient descent methods for minimizing certain convex functions on ℝ n . Currently prominent methods belonging to this class include the resolvent (proximal point) method and the bundle method in proximal form (considered as a sequence of serious steps). Other methods, such as a variant of the proximal point method given by Correa and Lemaréchal, can also fit within this framework, depending on how they are implemented. The convex functions covered by the analysis are those whose conjugates have subdifferentials that are locally upper Lipschitzian at the origin, a property generalizing classical regularity conditions.
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  • 91
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    Mathematical programming 86 (1999), S. 387-415 
    ISSN: 1436-4646
    Keywords: Key words: semi-infinite optimization – reduction approach – stationary point – strong stability – extended Mangasarian-Fromovitz constraint qualification Mathematics Subject Classification (1991): 90C30, 90C31, 90C34, 49M39
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    Notes: Abstract. The paper deals with semi-infinite optimization problems which are defined by finitely many equality constraints and infinitely many inequality constraints. We generalize the concept of strongly stable stationary points which was introduced by Kojima for finite problems; it refers to the local existence and uniqueness of a stationary point for each sufficiently small perturbed problem, where perturbations up to second order are allowed. Under the extended Mangasarian-Fromovitz constraint qualification we present equivalent conditions for the strong stability of a considered stationary point in terms of first and second derivatives of the involved functions. In particular, we discuss the case where the reduction approach is not satisfied.
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    Mathematical programming 86 (1999), S. 313-334 
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    Keywords: Key words: linear programming – potential functions – infeasible-interior-point methods – homogeneity – self-dual
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  • 93
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    Keywords: Key words: basis recovery – partition – principal pivot transforms – Balinski-Tucker tableaus – quadratic programming – linear complementarity problems – interior point methods – sufficient matrices – crossover – Criss-Cross method
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    Notes: Abstract. Optimal solutions of interior point algorithms for linear and quadratic programming and linear complementarity problems provide maximally complementary solutions. Maximally complementary solutions can be characterized by optimal partitions. On the other hand, the solutions provided by simplex–based pivot algorithms are given in terms of complementary bases. A basis identification algorithm is an algorithm which generates a complementary basis, starting from any complementary solution. A partition identification algorithm is an algorithm which generates a maximally complementary solution (and its corresponding partition), starting from any complementary solution. In linear programming such algorithms were respectively proposed by Megiddo in 1991 and Balinski and Tucker in 1969. In this paper we will present identification algorithms for quadratic programming and linear complementarity problems with sufficient matrices. The presented algorithms are based on the principal pivot transform and the orthogonality property of basis tableaus.
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    Mathematical programming 86 (1999), S. 417-431 
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    Keywords: Mathematics Subject Classification (1991): 90A11, 90B50, 90C90, 90D65
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    Notes: Abstract. We study the following decision-making scenario: A linear program is solved by a set of agents arranged hierarchically in a tree, where each agent decides the level of certain variables, and has a distinct objective function, known to all agents. Authority is reflected in two ways: Agents higher in the tree set their variables first; and agents that are siblings in the tree resolve their game by focusing on the Nash equilibrium that is optimum for the agent above them. We give a necessary and sufficient condition for such a hierarchy to be efficient (i.e., to have perfect coordination, to ultimately optimize the objective of the firm). We study problems related to designing a hierarchy (assigning decision makers to positions in the tree) in order to achieve efficiency or otherwise optimize coordination.
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    Mathematical programming 86 (1999), S. 533-563 
    ISSN: 1436-4646
    Keywords: Key words: generalized linear complementarity problem – non-interior continuation method – Newton method – Q-quadratical convergence Mathematics Subject Classification (1991): 90C33
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    Notes: Abstract. In this paper, we propose a non-interior continuation method for solving generalized linear complementarity problems (GLCP) introduced by Cottle and Dantzig. The method is based on a smoothing function derived from the exponential penalty function first introduced by Kort and Bertsekas for constrained minimization. This smoothing function can also be viewed as a natural extension of Chen-Mangasarian’s neural network smooth function. By using the smoothing function, we approximate GLCP as a family of parameterized smooth equations. An algorithm is presented to follow the smoothing path. Under suitable assumptions, it is shown that the algorithm is globally convergent and local Q-quadratically convergent. Few preliminary numerical results are also reported.
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  • 96
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    Mathematical programming 86 (1999), S. 463-473 
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    Keywords: Key words: semidefinite relaxations – quadratic programming Mathematics Subject Classification (1991): 20E28, 20G40, 20C20
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    Notes: Abstract. We demonstrate that if A 1,...,A m are symmetric positive semidefinite n×n matrices with positive definite sum and A is an arbitrary symmetric n×n matrix, then the relative accuracy, in terms of the optimal value, of the semidefinite relaxation $$\max_X\{\Tr(AX)\mid\, \Tr(A_iX)\le1,\,\,i=1,...,m;\,X\succeq0\} \eqno{\hbox{(SDP)}}$$ of the optimization program $$x^TAx\to\max\mid\, x^TA_ix\le 1,\,\,i=1,...,m \eqno{\hbox{(P)}}$$ is not worse than $$1-\frac{1}{{2\ln(2m^2)}}$$ . It is shown that this bound is sharp in order, as far as the dependence on m is concerned, and that a~feasible solution x to (P) with $$x^TAx\ge \frac{{\Opt(\hbox{{\rm SDP}})}}{{2\ln(2m^2)}} \eqno{(*)}$$ can be found efficiently. This somehow improves one of the results of Nesterov [4] where bound similar to (*) is established for the case when all Ai are of rank 1.
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    Mathematical programming 86 (1999), S. 161-185 
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    Keywords: Mathematics Subject Classification (1991): 90C10
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    Notes: Abstract. This paper considers the precedence constrained knapsack problem. More specifically, we are interested in classes of valid inequalities which are facet-defining for the precedence constrained knapsack polytope. We study the complexity of obtaining these facets using the standard sequential lifting procedure. Applying this procedure requires solving a combinatorial problem. For valid inequalities arising from minimal induced covers, we identify a class of lifting coefficients for which this problem can be solved in polynomial time, by using a supermodular function, and for which the values of the lifting coefficients have a combinatorial interpretation. For the remaining lifting coefficients it is shown that this optimization problem is strongly NP-hard. The same lifting procedure can be applied to (1,k)-configurations, although in this case, the same combinatorial interpretation no longer applies. We also consider K-covers, to which the same procedure need not apply in general. We show that facets of the polytope can still be generated using a similar lifting technique. For tree knapsack problems, we observe that all lifting coefficients can be obtained in polynomial time. Computational experiments indicate that these facets significantly strengthen the LP-relaxation.
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    Mathematical programming 70 (1995), S. 27-45 
    ISSN: 1436-4646
    Keywords: Convex polytopes ; Enumeration of faces ; Adjacency ; Segments
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    Notes: Abstract We introduce the concept of a segment of a degenerate convex polytope specified by a system of linear constraints, and explain its importance in developing algorithms for enumerating the faces. Using segments, we describe an algorithm that enumerates all the faces, in time polynomial in their number. The role of segments in the unsolved problem of enumerating the extreme points of a convex polytope specified by a degenerate system of linear constraints, in time polynomial in the number of extreme points, is discussed.
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    Mathematical programming 70 (1995), S. 47-72 
    ISSN: 1436-4646
    Keywords: Bilevel programming ; Nonlinear nonconvex ; Nondifferentiable optimization ; Economic planning ; Sensitivity analysis
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    Notes: Abstract This paper is concerned with general nonlinear nonconvex bilevel programming problems (BLPP). We derive necessary and sufficient conditions at a local solution and investigate the stability and sensitivity analysis at a local solution in the BLPP. We then explore an approach in which a bundle method is used in the upper-level problem with subgradient information from the lower-level problem. Two algorithms are proposed to solve the general nonlinear BLPP and are shown to converge to regular points of the BLPP under appropriate conditions. The theoretical analysis conducted in this paper seems to indicate that a sensitivity-based approach is rather promising for solving general nonlinear BLPP.
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    Mathematical programming 70 (1995), S. 123-148 
    ISSN: 1436-4646
    Keywords: Generalized equations ; Variational inequalities ; Nonlinear programming ; Sensitivity analysis ; Power series ; Strong regularity ; Constrained optimization ; Perturbation theory
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    Notes: Abstract We show that the solution of a strongly regular generalized equation subject to a scalar perturbation expands in pseudopower series in terms of the perturbation parameter, i.e., the expansion of orderk is the solution of generalized equations expanded to orderk and thus depends itself on the perturbation parameter. In the polyhedral case, this expansion reduces to a usual Taylor expansion. These results are applied to the problem of regular perturbation in constrained optimization. We show that, if the strong regularity condition is satisfied, the property of quadratic growth holds and, at least locally, the solutions of the optimization problem and of the associated optimality system coincide. If, in addition the number of inequality constraints is finite, the solution and the Lagrange multiplier can be expanded in Taylor series. If the data are analytic, the solution and the multiplier are analytic functions of the perturbation parameter.
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