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  • Articles  (17)
  • linear programming  (17)
  • Springer  (17)
  • International Union of Crystallography
  • 1985-1989  (17)
  • 1950-1954
  • Computer Science  (12)
  • Architecture, Civil Engineering, Surveying  (5)
  • Geosciences  (1)
  • Natural Sciences in General
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  • Articles  (17)
Publisher
  • Springer  (17)
  • International Union of Crystallography
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 43 (1989), S. 151-173 
    ISSN: 1436-4646
    Keywords: Conical projection methods ; Karmarkar's LP algorithm ; linear programming ; poly-nomial-time algorithms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The Linear Programming Problem is manipulated to be stated as a Non-Linear Programming Problem in which Karmarkar's logarithmic potential function is minimized in the positive cone generated by the original feasible set. The resulting problem is then solved by a master algorithm that iteratively rescales the problem and calls an internal unconstrained non-linear programming algorithm. Several different procedures for the internal algorithm are proposed, giving priority either to the reduction of the potential function or of the actual cost. We show that Karmarkar's algorithm is equivalent to this method in the special case in which the internal algorithm is reduced to a single steepest descent iteration. All variants of the new algorithm have the same complexity as Karmarkar's method, but the amount of computation is reduced by the fact that only one projection matrix must be calculated for each call of the internal algorithm.
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  • 2
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    Stochastic environmental research and risk assessment 3 (1989), S. 17-29 
    ISSN: 1436-3259
    Keywords: Stochastic optimization ; linear programming ; simplex method ; Karmarkar's method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Optimization of multi-reservoir systems operations is typically a very large scale optimization problem. The following are the three types of optimization problems solved using linear programming (LP): (i) deterministic optimization for multiple periods involving fine stage intervals, for example, from an hour to a week (ii) implicit stochastic optimization using multiple years of inflow data, and (iii) explicit stochastic optimization using probability distributions of inflow data. Until recently, the revised simplex method has been the most efficient solution method available for solving large scale LP problems. In this paper, we show that an implementation of the Karmarkar's interior-point LP algorithm with a newly developed stopping criterion solves optimization problems of large multi-reservoir operations more efficiently than the simplex method. For example, using a Micro VAX II minicomputer, a 40 year, monthly stage, two-reservoir system optimization problem is solved 7.8 times faster than the advanced simplex code in MINOS 5.0. The advantage of this method is expected to be greater as the size of the problem grows from two reservoirs to multiples of reservoirs. This paper presents the details of the implementation and testing and in addition, some other features of the Karmarkar's algorithm which makes it a valuable optimization tool are illuminated.
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  • 3
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    Mathematical programming 44 (1989), S. 27-41 
    ISSN: 1436-4646
    Keywords: Interior-point methods ; linear programming ; Karmarkar's algorithm ; polynomial-time algorithms ; logarithmic barrier function ; path following
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We describe a primal-dual interior point algorithm for linear programming problems which requires a total of $$O\left( {\sqrt n L} \right)$$ number of iterations, whereL is the input size. Each iteration updates a penalty parameter and finds the Newton direction associated with the Karush-Kuhn-Tucker system of equations which characterizes a solution of the logarithmic barrier function problem. The algorithm is based on the path following idea.
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  • 4
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    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.
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  • 5
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    Water resources management 3 (1989), S. 129-140 
    ISSN: 1573-1650
    Keywords: Waste load allocation ; water quality management ; multi-objective analysis ; linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract In an attempt to improve managing river water quality, this paper presents a model to a three-objective WLA problem using the constraint method in conjunction with the parametric linear programming technique. The three objectives considered are: (1) maximization of total waste load discharge, (2) minimization of the largest difference in equity between dischargers, and (3) maximization of the lowest allowable water quality standard.
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  • 6
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    Mathematical programming 41 (1988), S. 317-325 
    ISSN: 1436-4646
    Keywords: Parametric methods ; linear programming ; anti-cycling pivoting rules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The traditional perturbation (or lexicographic) methods for resolving degeneracy in linear programming impose decision rules that eliminate ties in the simplex ratio rule and, therefore, restrict the choice of exiting basic variables. Bland's combinatorial pivoting rule also restricts the choice of exiting variables. Using ideas from parametric linear programming, we develop anticycling pivoting rules that do not limit the choice of exiting variables beyond the simplex ratio rule. That is, any variable that ties for the ratio rule can leave the basis. A similar approach gives pivoting rules for the dual simplex method that do not restrict the choice of entering variables.
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  • 7
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    Mathematical programming 42 (1988), S. 125-133 
    ISSN: 1436-4646
    Keywords: Cycling ; degeneracy ; graph theory ; linear programming ; sensitivity analysis ; simplex method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
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  • 8
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    Mathematical programming 40 (1988), S. 165-181 
    ISSN: 1436-4646
    Keywords: Relaxation ; network ; integer programming ; linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The strategy of subdividing optimization problems into layers by splitting variables into multiple copies has proved useful as a method for inducing exploitable structure in a variety of applications, particularly those involving embedded pure and generalized networks. A framework is proposed in this paper which leads to new relaxation and restriction methods for linear and integer programming based on our extension of this strategy. This framework underscores the use of constructions that lead to stronger relaxations and more flexible strategies than previous applications. Our results establish the equivalence of all layered Lagrangeans formed by parameterizing the equal value requirement of copied variables for different choices of the principal layers. It is further shown that these Lagrangeans dominate traditional Lagrangeans based on incorporating non-principal layers into the objective function. In addition a means for exploiting the layered Lagrangeans is provided by generating subgradients based on a simple averaging calculation. Finally, we show how this new layering strategy can be augmented by an integrated relaxation/restriction procedure, and indicate variations that can be employed to particular advantage in a parallel processing environment. Preliminary computational results on fifteen real world zero-one personnel assignment problems, comparing two layering approaches with five procedures previously found best for those problems, are encouraging. One of the layering strategies tested dominated all non-layering procedures in terms of both quality and solution time.
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  • 9
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    Mathematical programming 40 (1988), S. 197-204 
    ISSN: 1436-4646
    Keywords: Greedy algorithms ; series parallel graphs ; linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract This note describes some sufficient conditions for the maximum or minimum of a weighted flow (the weights are on paths, and are derived from weights on the edges of the path), of given volume in a series parallel graph to be found by a greedy algorithm.
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  • 10
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    Mathematical programming 40 (1988), S. 183-195 
    ISSN: 1436-4646
    Keywords: Karmarkar's method ; linear programming ; inexact projections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Variants of Karmarkar's algorithm are given for solving linear programs with unknown optimal objective valuez *. These new methods combine the approach of Goldfarb and Mehrotra for relaxing the requirement that certain projections be computed exactly with the approach of Todd and Burrell for generating an improving sequence of lower bounds forz * using dual feasible solutions. These methods retain the polynomial-time complexity of Karmarkar's algorithm.
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  • 11
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    Mathematical programming 42 (1988), S. 135-145 
    ISSN: 1436-4646
    Keywords: Degeneracy ; dual infeasibility ; linear programming ; primal degeneracy ; simplex algorithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The Revised Primal Simplex algorithm, in its simplest form, has no defence against degeneracy. Various forms of the perturbation method are usually effective, but most offer no guarantee of avoiding all degeneracy, and can lead to numerical difficulties. This paper presents a method that avoids cycling and circling by taking a dual approach. The degenerate subproblem consists of all the original variables, but only the degenerate transformed constraints. The current primal objective, which may be mixed, is used. This subproblem may be solved using the dual simplex algorithm, starting from the current dual infeasible solution, and with a zero dual objective. If the dual algorithm terminates optimally then the whole problem is optimal (subject to primal feasibility). Otherwise the final solution provides a non-basic direction which improves the value of the mixed primal objective and moves away from the degenerate vertex. A purification algorithm then renders the solution basic and further improves the mixed objective.
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  • 12
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    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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  • 13
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    Water resources management 2 (1988), S. 21-34 
    ISSN: 1573-1650
    Keywords: Stochastic programming ; linear programming ; objective function ; synthetic streamflow ; reliability ; skewed ; random variable ; spill ; release ; storage ; free board
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract A generalized linear decision rule is presented which takes into account the aspect of spill in a multi-lag LDR model. The proposed rule incorporates past inflow experience to determine the optimum release rules based on a stochastic (linear) programming optimization model. It also prescribes a procedure of determining spill, should it occur, and the method of adjusting the release policy, accordingly, for the subsequent periods, which are directly affected by the spill of the current period. The use of the rule also makes it possible to produce a specification for a reservoir with a smaller capacity by taking liberal constraints on the reservoir freeboard during the monsoon months. The problem is solved, for the purpose of illustration, using the historical data of a river located in central India. Two synthetic streamflow series of a duration of 50 years each are generated under lognormal flow assumption. The prescribed release rules are applied to a hypothetical reservoir with the optimum capacity determined by the linear programming method, and the generated series as the inflow. The results and findings are quite satisfactory.
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  • 14
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    Water resources management 2 (1988), S. 103-121 
    ISSN: 1573-1650
    Keywords: Aquifer management ; groundwater quality ; waste disposal patterns ; net disposal gain ; analytic solutions ; linear programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The impact of optimal waste disposal patterns upon the maximum assimilative capacity of groundwater systems is investigated in cases where the simultaneous utilization of the same aquifer for water supply as well as for waste disposal is required. A groundwater quality management model that combines analytic solutions off the dimensionless advective-dispersive transport equation with linear programming is developed. Three different patterns of waste disposal are considered: a constant rate, a pulsing-type, and a continuously varying rate. Optimal schedules for all the patterns are determined for a wide range of the problem's parameters, and a critical evaluation of their benefits leads, eventually, to a complete series of useful guidelines. These guidelines can serve as a-priori criteria for the selection of the most suitable waste disposal patterns.
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  • 15
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    Water resources management 1 (1987), S. 143-154 
    ISSN: 1573-1650
    Keywords: Flood management ; large-scale systems ; linear programming ; deterministic inflows ; risk analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The Ottawa River System is a large-scale and complex system comprising 30 major reservoirs and 43 generating stations and has a long history of flooding that extends throughout the basin. Its operation aims primarily at meeting energy requirements but is largely affected by flood reduction and other interests such as nagivation, low flow augmentation, recreation and log driving. This paper gives a brief description of the system and of the linear programming optimization model (MORRO) that is currently used to establish operation rules in flood management. Risk analysis is outlined as a procedure to deviate from optimal policy in order to account for uncertainties in inflow forecast.
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  • 16
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    Mathematical programming 35 (1986), S. 173-192 
    ISSN: 1436-4646
    Keywords: Computational complexity ; average running time ; simplex algorithm ; linear programming ; linear complementarity problem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We show that a particular pivoting algorithm, which we call the lexicographic Lemke algorithm, takes an expected number of steps that is bounded by a quadratic inn, when applied to a random linear complementarity problem of dimensionn. We present two probabilistic models, both requiring some nondegeneracy and sign-invariance properties. The second distribution is concerned with linear complementarity problems that arise from linear programming. In this case we give bounds that are quadratic in the smaller of the two dimensions of the linear programming problem, and independent of the larger. Similar results have been obtained by Adler and Megiddo.
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  • 17
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    Mathematical programming 35 (1986), S. 193-224 
    ISSN: 1436-4646
    Keywords: Local improvement ; average performance of algorithms ; linear complementarity ; linear programming ; extremal set theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We present a general abstract model of local improvement, applicable to such diverse cases as principal pivoting methods for the linear complementarity problem and hill climbing in artificial intelligence. The model accurately predicts the behavior of the algorithms, and allows for a variety of probabilistic assumptions that permit degeneracy. Simulation indicates an approximately linear average number of iterations under a variety of probability assumptions. We derive theoretical bounds of 2en logn and en 2 for different distributions, respectively, as well as polynomial bounds for a broad class of probability distributions. We conclude with a discussion of the applications of the model to LCP and linear programming.
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