This paper is concerned with linearprogramming problems in which many of the constraints are handled implicitly by requiring that the vector of decision variables lie in a polyhedronX. It is shown that the simplex me...
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This paper is concerned with linearprogramming problems in which many of the constraints are handled implicitly by requiring that the vector of decision variables lie in a polyhedronX. It is shown that the simplex method can be implemented using a working basis whose size is the number of explicit constraints as long as the local structure ofX around the current point is known. Various ways of describing this local structure lead to known implementations whenX is defined by generalized or variable upper bounds or flow conservation constraints. In the general case a decomposition principle can be used to generate this local structure. We also show how to update factorizations of the working basis.
In this paper, we focus on large-scale linear programming problems with block angular structure for which the Dantzig-Wolfe decomposition method has been successfully applied. By considering the vague nature of human ...
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In this paper, we focus on large-scale linear programming problems with block angular structure for which the Dantzig-Wolfe decomposition method has been successfully applied. By considering the vague nature of human judgements, we assume that the decision maker may have a fuzzy goal for the objective function and fuzzy constraints for the coupling constraints. Having elicited the corresponding linear membership functions through the interaction with the decision maker, if we adopt the convex fuzzy decision for combining them, it is shown that, under some appropriate conditions, the formulated problem can be reduced to a number of independent linear subproblems and the overall satisficing solution for the decision maker is directly obtained just only solving the subproblems.
This paper describes a method and the corresponding algorithms for simplification of large-scale linear programming models. It consists of the elimination of the balance constraints (i.e. constraints with zero RHS ter...
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In this paper, we present an interactive fuzzy satisficing method for large-scale multiobjective linearprogramming problems with the block angular structure. By considering the vague nature of human judgements, we as...
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In this paper, we present an interactive fuzzy satisficing method for large-scale multiobjective linearprogramming problems with the block angular structure. By considering the vague nature of human judgements, we assume that the decision maker (DM) may have a fuzzy goal for each of the objective functions. Having elicited the corresponding linear membership functions, if the DM specifies the reference membership levels for all the membership functions, the corresponding Pareto optimal solution which is, in the minimax sense, nearest to the requirement or better than that if the reference membership levels are attainable can be obtained by solving the minimax problem. Here it is shown that the formulated minimax problem can be reduced to one master problem and a number of linear subproblems and the Pareto optimal solution together with the trade-off rate information between the membership functions can be obtained by applying the Dantzig-Wolfe decomposition method. In this way, the satisficing solution for the DM can be derived from Pareto optimal solutions by updating the current reference membership levels on the basis of the current levels of the membership functions together with the trade-off rates between the membership functions.
In this paper, we focus on large-scale multiobjective linearprogramming problems with the block angular structure. By considering the imprecise nature of human judgements, we assume that the decision maker may have a...
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In this paper, we focus on large-scale multiobjective linearprogramming problems with the block angular structure. By considering the imprecise nature of human judgements, we assume that the decision maker may have a fuzzy goal for each of the objective functions. Having elicited the corresponding linear membership functions through the interaction with the decision maker, we adopt the fuzzy decision for aggregating them. Then it is shown that the formulated problem can be reduced to one master problem and a number of linear subproblems and the satisficing solution for the decision maker can be obtained by directly applying the Dantzig-Wolfe decomposition method.
In this paper, a large-scale multiobjective block-angular linearprogramming problem involving fuzzy parameters is formulated by considering the experts' vague understanding of the nature of the parameters in the ...
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In this paper, a large-scale multiobjective block-angular linearprogramming problem involving fuzzy parameters is formulated by considering the experts' vague understanding of the nature of the parameters in the problem-formulation process. Using the α-level sets of fuzzy numbers, the corresponding nonfuzzy α-programming problem is introduced and the fuzzy goals of the decision maker are quantified by eliciting the membership functions. Through the introduction of an extended Pareto optimality concept, if the decision maker specifies the degree a and the reference membership values, the corresponding extended Pareto optimal solution can be obtained by solving the minimax problems for which the Dantzig-Wolfe decomposition method is applicable. Then a linearprogramming-based interactive fuzzy satisficing method for deriving a satisficing solution for the decision maker from an extended Pareto optimal solution set is presented.
We describe an active-set, cutting-plane approach called Constraint Optimal Selection Techniques (COSTs) and develop an efficient new COST for solving nonnegative linearprogramming problems. We give a geometric inter...
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We describe an active-set, cutting-plane approach called Constraint Optimal Selection Techniques (COSTs) and develop an efficient new COST for solving nonnegative linearprogramming problems. We give a geometric interpretation of the new selection rule and provide computational comparisons of the new COST with existing linearprogramming algorithms for some large-scale sample problems. (C) 2014 Elsevier Inc. All rights reserved.
The standard basis, which plays a fundamental role in simplex methodology, was recently extended to include a deficient case (with fewer columns than rows) by taking advantage of primal degeneracy. Computational resul...
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The standard basis, which plays a fundamental role in simplex methodology, was recently extended to include a deficient case (with fewer columns than rows) by taking advantage of primal degeneracy. Computational results have been favorable with dense implementations. In this paper, we propose a primal simplex algorithm using sparse LU factors of deficient bases. Amenable to real-world linearprogramming problems, which are often degenerate or even highly degenerate, the algorithm would solve them with potentially improved stability compared to the simplex algorithm. The proposed algorithm has been implemented and tested on a set of 50 Netlib test problems as well as a set of 15 much larger real-world problems, including 8 Kennington and 5 BPMPD problems. It significantly outperformed MINOS 5.3 in terms of both iteration counts and run time. In particular,. these results reveal that there is no inevitable correlation between an algorithm's inefficiency and degeneracy (contradicting common belief). (C) 2007 Elsevier Inc. All rights reserved.
Recently, computational results demonstrated remarkable superiority of a so-called "largest-distance" rule and "nested pricing" rule to other major rules commonly used in practice, such as Dantzig's original rule...
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Recently, computational results demonstrated remarkable superiority of a so-called "largest-distance" rule and "nested pricing" rule to other major rules commonly used in practice, such as Dantzig's original rule, the steepest-edge rule and Devex rule. Our computational experiments show that the simplex algorithm using a combination of these rules turned out to be even more efficient.
We revise the dual projective pivot algorithm using sparse rectangular LU factors. In each iteration, the proposed algorithm solves at most three triangular systems, while simplex algorithms solve four. Instead of the...
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We revise the dual projective pivot algorithm using sparse rectangular LU factors. In each iteration, the proposed algorithm solves at most three triangular systems, while simplex algorithms solve four. Instead of the classical basis, it uses a so-called pseudobasis ( a rectangular matrix having fewer columns than rows), thereby solving smaller linear systems with a potentially improved stability compared to simplex algorithms. Most importantly, it generates good search directions at a low cost. We report encouraging computational results on a set of 50 Netlib standard test problems as well as a set of 15 much larger real-world problems. A code named RDPPA 1.10 based on the proposed algorithm outperformed MINOS 5.51 significantly in terms of both iterations and run time. In particular, it appears that a high proportion of degenerate iterations need not imply many total iterations ( contradicting the common belief).
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