A shortest-route formulation of the mixed-model assembly line balancing problem is presented. Common tasks across models are assumed to exist and these tasks are performed in the same stations. The formulation is base...
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A shortest-route formulation of the mixed-model assembly line balancing problem is presented. Common tasks across models are assumed to exist and these tasks are performed in the same stations. The formulation is based on an algorithm which solves the single-model version of the problem. The mixed-model system is transformed into a single-model system with a combined precedence diagram. The model is capable of considering any constraint that can be expressed as a function of task assignments. (C) 1999 Elsevier Science B.V. All rights reserved.
We propose a neu method based on minimum mean cycle cancelling for multicommodity flow problems with separable convex cost ruling out saturated capacities. This method is inspired by the cycle cancelling method first ...
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We propose a neu method based on minimum mean cycle cancelling for multicommodity flow problems with separable convex cost ruling out saturated capacities. This method is inspired by the cycle cancelling method first worked out by Goldberg and Tarjan for minimum cost circulations (A.V. Goldberg, R.E. Tarjan, Finding minimum-cost circulation by cancelling negative cycles, JACM 36 (4), 1989, pp. 873-886). Convergence of the method is formally proved and a variant with a more flexible selection of cycles is proposed. Also. we report some computational experience on the message routing problem in telecommunication networks using actual and randomly generated networks. (C) 2000 Elsevier Science B.V. All rights reserved.
The trade-off between false sharing elimination and aggregation in distributed shared memory (DSM) systems has a major effect on their performance. Some studies in this area show that fine grain access is advantageous...
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The trade-off between false sharing elimination and aggregation in distributed shared memory (DSM) systems has a major effect on their performance. Some studies in this area show that fine grain access is advantageous, while others advocate the use of large coherency units. One way to resolve the trade-off is to dynamically adapt the granularity to the application memory access pattern. In this paper, we propose a novel technique for implementing multiple sharing granularities over page-based DSMS. We present protocols for efficient switching between small and large sharing units during runtime. We show that applications may benefit from adapting the memory sharing to the memory access pattern, using both coarse grain sharing and fine grain sharing interchangeably in different stages of the computation. Our experiments show a substantial improvement in the performance using adapted granularity level over using a fixed granularity level. (C) 2000 Elsevier Science Inc. All rights reserved.
Grid protocols and technologies are being adopted in a wide variety of academic, government, and industrial environments, and a growing body of research-oriented literature in grid computing is being compiled. However...
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Grid protocols and technologies are being adopted in a wide variety of academic, government, and industrial environments, and a growing body of research-oriented literature in grid computing is being compiled. However, there is a need for educational material that is suitable for classroom use. This paper describes topics, exercises, and experiences of teaching grid computing at two different universities. Course material in grid computing can be grouped into several knowledge areas. The focus in this paper is on grid programming, i.e., developing grid-enabled services using the Globus toolkit. Assessment data shows that with preparatory material and hands-on exercises, undergraduate computer science students can master grid programming. Topics and exercises for security, network programming, Web services, and grid programming are described. Recommendations include using stand-alone containers on individual student computers and following a first grid programming exercise that builds confidence with at least one more elaborate grid programming exercise.
We give algorithms for finding the k shortest paths (not required to be simple) connecting a pair of vertices in a digraph. Our algorithms output an implicit representation of these paths in a digraph with n vertices ...
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We give algorithms for finding the k shortest paths (not required to be simple) connecting a pair of vertices in a digraph. Our algorithms output an implicit representation of these paths in a digraph with n vertices and m edges, in time O(m + n log n + k). We can also find the k shortest paths from a given source s to each vertex in the graph, in total time O(m + n log n + kn). We describe applications to dynamic programming problems including the knapsack problem, sequence alignment, maximum inscribed polygons, and genealogical relationship discovery.
This paper presents a specialized network procedure for the solution of pure goal network programs with preemptive priorities. The specialization solves such goal network programs efficiently since it requires a modif...
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This paper presents a specialized network procedure for the solution of pure goal network programs with preemptive priorities. The specialization solves such goal network programs efficiently since it requires a modification only in the pricing rule of the network simplex algorithm. The algorithm is used to solve multiple goal network programs that arise in the assignment of naval personnel to jobs. Computational experience indicates that the specialization dominates the sequential linear goal programming procedure. (C) 1998 Elsevier Science B.V.
The K shortest paths problem has been extensively studied for many years. Efficient methods have been devised, and many practical applications are known. Shortest hyperpath models have been proposed for several proble...
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The K shortest paths problem has been extensively studied for many years. Efficient methods have been devised, and many practical applications are known. Shortest hyperpath models have been proposed for several problems in different areas, for example in relation with routing in dynamic networks. However. the K shortest hyperpaths problem has not yet been investigated. In this paper we present procedures for finding the K shortest hyperpaths in a directed hypergraph. This is done by extending existing algorithms for K shortest loopless paths. Computational experiments on the proposed procedures are performed, and applications in transportation. planning and combinatorial optimization are discussed. (C) 2003 Elsevier Ltd. All rights reserved.
In some applications a minimum cost transportation model arises where supplies are fixed while demands may simultaneously vary. In this paper we analyse the structure of such a model and propose several techniques to ...
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In some applications a minimum cost transportation model arises where supplies are fixed while demands may simultaneously vary. In this paper we analyse the structure of such a model and propose several techniques to describe its behaviour. Our approach is founded on the concept of optimal region, i.e., the subset of demand vectors where a given basic tree is optimal. The proposed algorithm consists in different pivoting strategies designed to: 1. build up a minimal list of basic trees such that the associated optimal regions cover the set of feasible demand vectors;2. analyse the effects of either opening a new supplier or closing an existing one;3. suitably treat the dual degenerate case by building up a minimal representation of every maximal region where the optimal value is linear in the demand vector. Computational complexity is discussed and numerical examples are given. (C) 2002 Elsevier Science B.V. All rights reserved.
The multiperiod assignment problem, a specialization of the three dimensional assignment problem, is an optimization model that describes the situation of assigning people to activities, or jobs over time. We consider...
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The multiperiod assignment problem, a specialization of the three dimensional assignment problem, is an optimization model that describes the situation of assigning people to activities, or jobs over time. We consider the most general case which has both a cost of assigning a person to an activity in each time period, and a cost of transferring the person from one activity in each period to another activity in the next period. In general, the number of time periods need not equal the number of persons and activities. We present a new formulation of the multiperiod assignment problem, that of an integer, multicommodity network flow model. The special structure of the model allows us to find a good feasible solution relatively quickly by a shortest path heuristic algorithm. We discuss a new branch and bound algorithm for solving this problem to optimality. The subproblems of the branch and bound tree are evaluated by solving a set of special-structured, shortest path problems all of which can be solved in order n[SUP2]T time, where n is the number of persons and activities, and T is the number of time periods. We present computational tests of the algorithm on moderately sized problems. [ABSTRACT FROM AUTHOR]
We are interested in order promising models for supply chain management in the context of firms involved in eCommerce. In this context, buyers and suppliers constantly exchange information. All parties update producti...
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We are interested in order promising models for supply chain management in the context of firms involved in eCommerce. In this context, buyers and suppliers constantly exchange information. All parties update production, warehousing, and distribution plans based on negotiations involving product price, features, and due dates. One interesting question, from the supplier's point of view, is how a supplier firm should take part in these negotiations. Of particular interest to us at this point in time is to build an optimization-based decision support system (DSS) that will help an agent of the firm promise orders, i.e., quote due dates and prices. We present a model and illustrate it with a small example to show how the DSS addresses a useful need. (c) 2005 Elsevier B.V. All rights reserved.
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