Network decomposition-based benchmark results for the discrete time-cost tradeoff problem

In project management, the project duration can often be compressed by accelerating some of its activities at an additional expense. This is the so-called time–cost tradeoff problem which has been extensively studied in the past. However, the discrete version of the problem which is of great practical relevance, did not receive much attention so far. Given a set of modes (time–cost pairs) for each activity, the objective of the discrete time–cost tradeoff problem is to select a mode for each activity so that the total cost is minimized while meeting a given project deadline. The discrete time–cost tradeoff problem is a strongly -hard optimization problem for general activity networks. In terms of what current state-of-art algorithms can do, instances with (depending on the structure of the network and the number of processing alternatives per activity) no more than 20–50 activities can be solved to optimality in reasonable amount of time. Hence, heuristics must be employed to solve larger instances. To evaluate such heuristics, lower bounds are needed. This paper provides lower and upper bounds using column generation techniques based on “network decomposition”. Furthermore, a computational study is provided to demonstrate that the presented bounds are tight and that large and hard instances can be solved in short run-time

Zum Problem der taktisch-operativen Entscheidung zwischen Eigen- oder Fremdfertigung

Summary in EnglishAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 351 (374) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Improved Lower Bounds for the Proportional Lot Sizing and Scheduling Problem

Where standard MIP--solvers fail to compute optimum objective function values for certain MIP--model formulations, lower bounds may be used as a point of reference for evaluating heuristics. In this paper, we compute lower bounds for the multi--level proportional lot sizing and scheduling problem with multiple machines (PLSP--MM). Four approaches are compared: Solving LP--relaxations of two different model formulations, solving a relaxed MIP--model formulation optimally, and solving a Lagrangean relaxation. Keywords: Multi--level lot sizing, scheduling, lower bounds, PLSP 1 Introduction The problem we are focussing at, can be described as follows: Several items are to be produced in order to meet some known (or estimated) dynamic demand without backlogs and stockouts. Precedence relations among these items define an acyclic gozinto--structure of the general type. In contrast to many authors who allow demand for end items only, now, demand may occur for all items including component ..

A genetic algorithm for multi-level, multi-machine lot sizing and scheduling

SIGLEAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 351 (415) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Fallbasiertes Schliessen auf Methoden zur Produktionsplanung

Available from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, D-21400 Kiel W 351 (433) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Ablauforganisation bei Serienproduktion in Fliessfertigungssystemen

Available from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, D-21400 Kiel W 351 (431) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

On the amount and timing of project payments with hints to customary contracting in Germany

A huge number of publications deal with project scheduling and very often the objective is to minimize the makespan. We claim that in the real world money counts. Therefore, we review how project payments can be defined in practice. The issues of contracting and bidding are discussed to demonstrate that a whole universe of specific model formulations would be needed to cover real situations

A cellular automaton based heuristic for multi-level lot sizing and scheduling

SIGLEAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 351 (331) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Short-term management of lot production

SIGLEAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 351 (480) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Parameter controlled instance generation for lot sizig problems

SIGLEAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 351 (412) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman