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APPROXIMATION ALGORITHMS FOR THE DISCRETE TIMECOST TRADEOFF PROBLEM
, 1998
"... Due to its obvious practical relevance, the TimeCost Tradeoff Problem has attracted the attention of many researchers over the last forty years. While the Linear TimeCost Tradeoff Problem can be solved in polynomial time, its discrete variant is known to be NPhard. We present the first approximat ..."
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Due to its obvious practical relevance, the TimeCost Tradeoff Problem has attracted the attention of many researchers over the last forty years. While the Linear TimeCost Tradeoff Problem can be solved in polynomial time, its discrete variant is known to be NPhard. We present the first approximation algorithms for the Discrete TimeCost Tradeoff Problem. Specifically, given a fixed budget we consider the problem of finding a shortest schedule for a project. We give an approximation algorithm with performance ratio 3/2 for the class of projects where all feasible durations of activities are either 0, 1, or 2. We extend our result by giving approximation algorithms with performance guarantee O(log l), where l is the ratio of the maximum duration of any activity to the minimum nonzero duration of any activity. Finally, we discuss bicriteria approximation algorithms which compute schedules for a given deadline or budget such that both project duration and cost are within a constant factor of the duration and cost of an optimum schedule for the given deadline or budget.
Applications of Network Optimization
 Network Models, volume 7 of Handbooks in Operations Research and Management Science
, 1995
"... Network optimization has always been a core problem domain in operations research, as well as in computer science, applied mathematics, and many fields of engineering and management. Network optimization problems arise in a variety of situations, and often in situations that apparently are quite unr ..."
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Network optimization has always been a core problem domain in operations research, as well as in computer science, applied mathematics, and many fields of engineering and management. Network optimization problems arise in a variety of situations, and often in situations that apparently are quite unrelated to networks. These applications are scattered throughout the literature and until recently no single paper, book, or any other reference, summarized these applications. Consequently, the research and practitioner community has not fully appreciated the richness of these applications. This paper attempts to partially satisfy this important need by presenting a collection of applications of the following fundamental network optimization problems: the shortest path problem, the maximum flow problem, the minimum cost flow problem, assignment and matching problems, and the minimum spanning tree problem. We describe 25 applications of these problems and provide references for more than 100 additional applications. This paper is intended to provide an appreciation for the pervasiveness of network optimization problems. We hope that this paper will stimulate researchers and practitioners to model more decisions problems within the framework of network optimization.
New DistanceDirected Algorithms for Maximum Flow and Parametric Maximum Flow Problems
, 1987
"... ..."
Distancedirected augmenting path algorithms for maximum flow and parametric maximum flow problems
 Naval Research Logistics
, 1991
"... Until recently, fast algorithms for the maximum flow problem have typically proceeded by constructing layered networks and establishing blocking flows in these networks. However, in recent years, new distancedirected algorithms have been suggested that do not construct layered networks but instead ..."
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Cited by 4 (1 self)
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Until recently, fast algorithms for the maximum flow problem have typically proceeded by constructing layered networks and establishing blocking flows in these networks. However, in recent years, new distancedirected algorithms have been suggested that do not construct layered networks but instead maintain a distance label with each node. The distance label of a node is a lower bound on the length of the shortest augmenting path from the node to the sink. In this article we develop two distancedirected augmenting path algorithms for the maximum flow problem. Both the algorithms run in O(n 2 m) time on networks with n nodes and m arcs. We also point out the relationship between the distance labels and layered networks. Using a scaling technique, we improve the complexity of our distancedirected algorithms to O(nm log U), where U denotes the largest arc capacity. We also consider applications of these algorithms to unit capacity maximum flow problems and a class of parametric maximum flow problems. t i
An Analysis of Several New Product Performance Metrics
, 2000
"... For most #rms, new product development is the engine for growth and pro#tability. A #rm's new product success depends on its ability to manage the product development process in a way that employs scarce resources to achieve the goal of the #rm as well as the speci#c project's objectives. ..."
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For most #rms, new product development is the engine for growth and pro#tability. A #rm's new product success depends on its ability to manage the product development process in a way that employs scarce resources to achieve the goal of the #rm as well as the speci#c project's objectives. Simple and measurable performance metrics have been proposed and applied in order to monitor and compensate the development teams. In this paper, we develop a modeling framework in order to analyze the implications of setting managerial priorities for three commonly used new product performance metrics: 1) timetomarket, 2) product performance, and 3) total development cost. We model new product development as a product performance production' process that requires scarce development resources. Setting a target for development teams for each of these performance metrics can constrain this performance production process and thereby aect the other performance metrics. We model the constrained process a...
Resourceconstrained project scheduling: Past work and new directions
 Department of Industrial and Systems Engineering, University of Florida
, 2001
"... This report summarizes past work in resourceconstrained project scheduling problems (RCPSP) and also presents a new RCPSP with a specialized minimum cost objective function. This new RCPSP model focuses on singleresource problems with resource consumption and late delivery costs. This model applie ..."
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This report summarizes past work in resourceconstrained project scheduling problems (RCPSP) and also presents a new RCPSP with a specialized minimum cost objective function. This new RCPSP model focuses on singleresource problems with resource consumption and late delivery costs. This model applies, for example, to a general contractor or subcontractor in the construction industry facing project deadlines with limited resources and penalties for late completion. We develop a new binpacking based algorithm to provide good solutions for this problem and describe some computational experience with this algorithm. This paper is separated into two distinct parts. Part 1 (Sections 1 through 5) summarizes the vast literature on RCPSPs and categorizes this literature. Part 2 (Section 6) presents our new RCPSP variant and our heuristic algorithm. 1. Introduction and Classification of RCPSP Problems Resource constrained project scheduling problems (RCPSPs) involve assigning jobs or tasks to a resource or set of resources with limited capacity in order to meet some predefined objective. As we will see, many different objectives are possible and these depend on the goals of the decision maker, but
Generating Schedules to Maximize Quality
, 2004
"... Abstract. In knowledge generating production processes such as intelligence gathering and news reporting, the quality of the result produced by a given activity depends on its duration, and, due to resource limitations and process deadlines, tradeoffs must invariably be made regarding how much time ..."
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Abstract. In knowledge generating production processes such as intelligence gathering and news reporting, the quality of the result produced by a given activity depends on its duration, and, due to resource limitations and process deadlines, tradeoffs must invariably be made regarding how much time to devote to various activities to achieve maximum overall effect. In essense, some activities must be executed in faster time cycles than would be desirable under nonconstraining circumstances, with consequent degradation of process quality. In this paper, we consider this type of scheduling problem, which we refer to generally as quality maximization. Starting with normal resourceconstrained project scheduling problem (RCPSP) assumptions, we define a new type of scheduling problem by additionally associating a quality profile with each activity in the project. Quality profiles have an “anytime ” property, implying that activities can be terminated at any point, with the quality of the output being proportional to duration. Instead of finishing all activities as fast as possible, the goal of scheduling in this context is to maximize the overall quality given a hard project due date. We formulate this quality maximization problem as a constraintbased optimization problem, and present a new constraint posting algorithm for solving this problem that incorporates a linear optimization program. Different constraint posting heuristics are defined and evaluated on a set of quality maximization RCPSP problems constructed from standard reference RCPSP problems. The experimental results show the overall effectiveness of our approach for generating schedules to maximize quality. And ratiobased heuristics provide a promising starting point for stochastic sampling or other schedule refining techniques by solving 100 % problems without backtracking. 1
Coordination and incentive contracts in project management under asymmetric information
, 2005
"... We study the problem of the manager of a project consisting of two subprojects or tasks which are outsourced to different subcontractors. The project manager earns more revenue from the project if it is completed faster, but he cannot observe how hard subcontractors work, only the stochastic durati ..."
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We study the problem of the manager of a project consisting of two subprojects or tasks which are outsourced to different subcontractors. The project manager earns more revenue from the project if it is completed faster, but he cannot observe how hard subcontractors work, only the stochastic duration of their tasks. We derive the optimal linear incentive contracts to offer to the subcontractors when the tasks are conducted in series or in parallel. We compare them to the fixedprice contracts often encountered in practice, and discuss when incentive contracts lead to bigger performance improvement. We characterize how the incentive contracts vary with the subcontractors ’ risk aversion and cost of effort, the marginal effect of subcontractor effort, and the variability of task durations. We find that this dependence is sometimes counterintuitive in nature. For instance, for parallel tasks, if the first agent’s task is on the critical path and his variability increases, the project manager should induce the first agent to work less hard and the second agent to work harder.
Decision support and optimization in shutdown and turnaround scheduling
 INFORMS J. Computing
, 2010
"... informs doi 10.1287/ijoc.1100.0393 ..."
Chapter 1 Applications of Network Optimization
"... Highways, telephone lines, electric power systems, computer chips, water delivery systems, and rail lines: these physical networks, and many others, are familiar to all of us. In each of these problem settings, we often wish to send some good(s) (vehicles, messages, electricity, or water) from one p ..."
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Highways, telephone lines, electric power systems, computer chips, water delivery systems, and rail lines: these physical networks, and many others, are familiar to all of us. In each of these problem settings, we often wish to send some good(s) (vehicles, messages, electricity, or water) from one point to another, typically as