A multifacility location problem on median spaces

AbstractThis paper is concerned with the problem of locating n new facilities in the median space when there are k facilities already located. The objective is to minimize the weighted sum of distances. Necessary and sufficient conditions are established. Based on these results a polynomial algorithm is presented. The algorithm requires the solution of a sequence of minimum-cut problems. The complexity of this algorithm for median graphs and networks and for finite median spaces with ¦V¦points is O(¦V¦3 + ¦V¦ψ(n)), where ψ(n) is the complexity of the applied maximum-flow algorithm. For a simple rectilinear polygon P with N edges and equipped with the rectilinear distance the analogical algorithm requires O(N + k(logN + logk + ψ(n))) time and O(N + kψ(n)) time in the case of the vertex-restricted multifacility location problem

Applications of network optimization

Includes bibliographical references (p. 41-48).Ravindra K. Ahuja ... [et al.]

Optimal location of single and multiple obnoxious facilities: Algorithms for the maximin criterion under different norms.

This thesis investigates the computational problem of locating obnoxious (undesirable) facilities in a way that minimizes their effect on a given set of clients (e.g. population centres). Supposing that the undesirable effects of such a facility on a given client are a decreasing function of the distance between them the objective is to locate these facilities as far away as possible from the given set of clients, subject to constraints that prevent location at infinity. Emphasis is given to the MAXIMIN criterion which is to maximize the minimum client-to-facility distance. Distances are measured either in the Euclidean or the rectilinear metric. The properties of the optimal solution to the single facility problem are viewed from different, seemingly unrelated, perspectives ranging from plane geometry to duality theory. In particular, duality results from a mixed integer programming model are used to derive new properties of the optimal solution to the rectilinear problem. A new algorithm is developed for the rectilinear problem where the feasible region is a convex polygon. Unlike previous approaches, this method does not require linear programming at all. In addition to this, an interactive graphical approach is proposed as a site-generation tool used to identify potential locations in realistic problems. Its main advantages are that it requires minimal user intervention and makes no assumptions regarding the feasible region. It has been applied in large scale problems with up to 1000 clients, whereas the largest reported application so far involved 10 clients. Alternative models are presented for the multi-facility problem as well. Each of them is based on different assumptions and is applicable to specific situations. Moreover, an algorithm is established for the two-facility problem based on the properties of the optimal solution. To the best of our knowledge this is the first attempt to address this problem in the plane. Finally, a number of unresolved issues, especially in the multi-facility problem, are outlined and suggested as further research topics

Solving the Capacitated Multifacility Weber Problem approximately

In this study, we consider the capacitated multifacility Weber problem which is concerned with locating m facilities in the plane, and allocating their limited capacities to n customers at minimum total cost. In this group of location-allocation problems, the only cost dealt with is the transportation cost that is proportional to the distance between the facility and the customer. The capacities of each facility and the demands and the locations of each customer are predetermined and given as parameters. This problem is an intractable non-convex optimization problem and difficult to solve. Therefore, using approximation strategies to compute efficient and accurate lower and upper bounds for the capacitated multifacility Weber problem can be a good approach. We first concentrate on the alternating location allocation heuristics. Then we continue with the discretization strategies and the Lagrangean relaxations of the approximating models. Some specific lower bounding algorithms are also defined by using the special properties of some of the distance functions. In addition to them, the relaxation of the main model is investigated and a Lagrangean heuristic is devised. In this heuristic, either a linear relaxation or exact solution of the Lagrangean subproblem is found by using column generation and branch and price algorithms combined with concave minimization. Although an exact solution methodology is not found, the approximation methods give accurate results. The tight bounds calculated by using these algorithms can be convenient in searching the exact solutions for this group of problems

Multifacility location with imprecise data

Ankara : The Department of Industrial Engineering and the Institute of Engineering and Science, Bilkent Univ., 1994.Thesis (Master's) -- Bilkent University, 1994.Includes bibliographical references leaves 75-78.Locational decisions often suffer from lack of precise data. In this study, we consider a class of multifacility location problems where the demands of existing and new facilities are unknown, with a known set of possible realizations. The set may be finite or infinite. In the latter case, the data is assumed to be of interval type. We use various criteria to evaluate candidate solutions to these problems and build a framework for decision making.Demir, Muhittin HakanM.S

Discrete Convex Functions on Graphs and Their Algorithmic Applications

The present article is an exposition of a theory of discrete convex functions on certain graph structures, developed by the author in recent years. This theory is a spin-off of discrete convex analysis by Murota, and is motivated by combinatorial dualities in multiflow problems and the complexity classification of facility location problems on graphs. We outline the theory and algorithmic applications in combinatorial optimization problems

A review of network location theory and models

Cataloged from PDF version of article.In this study, we review the existing literature on network location problems. The study has a broad scope that includes problems featuring desirable and undesirable facilities, point facilities and extensive facilities, monopolistic and competitive markets, and single or multiple objectives. Deterministic and stochastic models as well as robust models are covered. Demand data aggregation is also discussed. More than 500 papers in this area are reviewed and critical issues, research directions, and problem extensions are emphasized.Erdoğan, Damla SelinM.S