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  • Articles  (9)
  • linear programming  (5)
  • algorithm  (4)
  • 2020-2022
  • 1985-1989  (9)
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  • Economics  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Computational economics 2 (1989), S. 17-36 
    ISSN: 1572-9974
    Keywords: Modeling systems ; modeling languages ; linear programming ; production problems ; transportation problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract In recent years a number of integrated modeling systems have been developed which combine modeling languages with database capabilities to greatly increase the productivity of linear programming, nonlinear programming, and simultaneous equation model builders (Palmer, 1984, Meeraus, 1983, Geoffrion, 1986). Among these systems is GAMS which was developed at the World Bank by Alexander Meeraus. Alongside the development of these systems Arthur Geoffrion has created a general framework for model development which he calls ‘Structured Modeling’. This paper compares the GAMS system to Geoffrion's framework to show (1) which of the capabilities of GAMS are and are not captured in the structured modeling framework and (2) which of the concepts in the structured modeling framework are and are not included in the GAMS system. Notational comparisons are made using the implementation of Structured Modeling presented in Geoffrion (1986a) and the version of GAMS presented in Brooke, Kendrick and Meeraus (1988). The capabilities of the two systems are compared on the basis of a set of characteristics that are considered essential in a modeling system (Fourer, 1983, Krishnan, 1985, Geoffrion, 1986a, 1986b, 1987). The rest of the paper is organized as follows. The structural elements and the organization of each system are introduced through the use of a simple example. A comparison of the two system is then provided. The paper closes with a discussion of user interfaces which may improve the systems.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Computational economics 2 (1989), S. 197-219 
    ISSN: 1572-9974
    Keywords: Market equilibrium ; spatial price ; algorithm ; progressive equilibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract In this paper we consider the solution of large-scale market equilibrium problems with linear transaction costs which can be formulated as strictly convex quadratic programming problems, subject to supply and demand constraints. In particular, we introduce two new classes of progressive equilibration algorithms, which retain the simplicity of the original cyclic ones in that at each step either the supply or demand market equilibrium subproblem can be solved explicitly in closed form. However, rather than equilibrating the markets in cyclic manner, the next market to be equilibrated is selected in a more strategic fashion. We then provide qualitative results for the entire family of progressive equilibration algorithms, i.e., the rate of convergence and computational complexity. We discuss implementation issues and give computational results for large-scale examples in order to illustrate and give insights into the theoretical analysis. Furthermore, we show that one of the new classes of algorithms, the ‘good-enough’ one, is computationally the most efficient. Theoretical results are important in that the relative efficiency of different algorithms need no longer be language, machine, or programmer dependent. Instead, the theory can guide both practitioners and researchers in ensuring that their implementation of these algorithms is, indeed, good. Since an equivalent quadratic programming problem arises in a certain class of constrained matrix problems, our results can be applied there, as well. Finally, since more general asymmetric multicommodity market equilibrium problems can be solved as series of the type of problems considered here, the result$ are also applicable to such equilibrium problems.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 14 (1988), S. 41-59 
    ISSN: 1572-9338
    Keywords: Parallel algorithms ; SOR ; gradient projection ; linear programming ; linear complementarity problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract A gradient projection successive overrelaxation (GP-SOR) algorithm is proposed for the solution of symmetric linear complementary problems and linear programs. A key distinguishing feature of this algorithm is that when appropriately parallelized, the relaxation factor interval (0, 2) isnot reduced. In a previously proposed parallel SOR scheme, the substantially reduced relaxation interval mandated by the coupling terms of the problem often led to slow convergence. The proposed parallel algorithm solves a general linear program by finding its least 2-norm solution. Efficiency of the algorithm is in the 50 to 100 percent range as demonstrated by computational results on the CRYSTAL token-ring multicomputer and the Sequent Balance 21000 multiprocessor.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 14 (1988), S. 245-289 
    ISSN: 1572-9338
    Keywords: 90C27 ; 68Q15 ; 68Q25 ; 68Rxx ; Parallel computer ; computational complexity ; polylog parallel algorithm ; P-completeness ; sorting ; shortest paths ; minimum spanning tree ; matching ; maximum flow ; linear programming ; knapsack ; scheduling ; traveling salesman ; dynamic programming ; branch and bound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract This is a review of the literature on parallel computers and algorithms that is relevant for combinatorial optimization. We start by describing theoretical as well as realistic machine models for parallel computations. Next, we deal with the complexity theory for parallel computations and illustrate the resulting concepts by presenting a number of polylog parallel algorithms andP-completeness results. Finally, we discuss the use of parallelism in enumerative methods.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Computational economics 1 (1988), S. 53-72 
    ISSN: 1572-9974
    Keywords: Knowledge-based system ; PM system ; production and distribution problems ; linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract Software for production and distribution problems has evolved from FORTRAN programs, to matrix generators, to modeling languages such as GAMS, AMPL, and Structured Modeling. One of the next steps in the evolution of this class of software is to knowledge-based systems. Such systems provide a guided interface for problem input, permit qualitative inference about the problem, and provide a means of creating the problem description in the form required by modeling languages. This paper is written for economists and management scientists who have experience with production and distribution modeling but limited familiarity with knowledge-based systems. The paper describes the PM System which was developed by Krishnan to analyze and model linear programming production and distribution problems. The system is written in PROLOG. Elements of the Mexican steel industry model by Kendrick, Meeraus, and Alatorre are used to illustrate the interface dialog, the PM language, and the transformations which are required to translate the model into the form required by the Structured Modeling system. Illustrations are provided of the use of the system for answering queries and modifying the problem.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 6 (1986), S. 147-160 
    ISSN: 1572-9338
    Keywords: Public sector ; locational equity ; tree network ; algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Classical location theories and models were initially developed for the private sector, so that the related operational research literature has emphasized performance measures of efficiency and effectiveness. For public sector applications, measures of equity become important, yet such measures have received little formal treatment. This paper suggests a locational equity measure, the variance measure, and investigates its properties for tree networks. A fast algorithm (O(M)) to locate the minimum variance point on a tree network is developed, and some numerical results illustrate the variance optimal location.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 6 (1986), S. 291-310 
    ISSN: 1572-9338
    Keywords: Capacitated location-routing ; integer programming ; algorithm ; least cost
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract In location-routing problems, the objective is to locate one or many depots within a set of sites (representing customer locations or cities) and to construct delivery routes from the selected depot or depots to the remaining sites at least system cost. The objective function is the sum of depot operating costs, vehicle acquisition costs and routing costs. This paper considers one such problem in which a weight is assigned to each site and where sites are to be visited by vehicles having a given capacity. The solution must be such that the sum of the weights of sites visited on any given route does not exceed the capacity of the visiting vehicle. The formulation of an integer linear program for this problem involves degree constraints, generalized subtour elimination constraints, and chain barring constraints. An exact algorithm, using initial relaxation of most of the problem constraints, is presented which is capable of solving problems with up to twenty sites within a reasonable number of iterations.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 5 (1985), S. 599-612 
    ISSN: 1572-9338
    Keywords: Microcomputers ; spreadsheets ; linear programming ; optimization ; software
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract This paper discusses the advantages of using spreadsheets for problem specification and report generation in optimization projects. It summarizes some of the mathematical programming software which is compatible with popular spreadsheets. A small production planning problem is used to illustrate the steps in input and processing of the results. Two programs are compared in detail.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 4 (1985), S. 103-121 
    ISSN: 1572-9338
    Keywords: Minimax ; games ; strategy ; matrix ; chess ; algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Computer game-playing programs repeatedly calculate minimax elements μ = min i max j M ij of large pay off matricesM ij . A straightforwardrow-by-row calculation of μ scans rows ofM ij one at a time, skipping to a new row whenever an element is encountered that exceeds a current minimax. Anoptimal calculation, derived here, scans the matrix more erratically but finds μ after testing the fewest possible matrix elements. Minimizing the number of elements tested is reasonable when elements must be computed as needed by evaluating future game positions. This paper obtains the expected number of tests required when the elements are independent, identically distributed, random variables. For matrices 50 by 50 or smaller, the expected number of tests required by the row-by-row calculation can be at most 42% greater than the number for the optimal calculation. When the numbersR, C of rows and columns are very large, both calculations require an expected number of tests nearRC/InR.
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