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An exact procedure for the unconstrained weighed earliness-tardiness project scheduling problem.

By M Vanhoucke, Erik Demeulemeester and Willy Herroelen


In this paper we study the unconstrained project scheduling problem with weighted earliness-tardiness penalty costs subject to zero-lag finish-start precedence constraints. Each activity of this unconstrained project scheduling problem has a known deterministic due date, a unit earliness penalty cost and a unit tardiness penalty cost. The objective is to schedule the activities in order to minimize the weighted earliness-tardiness penalty cost of the project, in the absence of constraints on the use of resources. With these features the problem setting become highly attractive in just-in-time environments.We introduce a two-step recursive algorithm. The first step consists of a forward pass procedure which schedules the activities such that they finish at their due date or later. The second step applies a recursive search in which the activities are eventually shifted backwards (topwards time zero) in order to minimize the weighted earliness-tardiness cost of the project. The procedure has been coded in Visual C++, version 4.0 under Windows NT 4.0 and has been validated on a randomly generated data set.Scheduling;

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