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

Scheduling of project networks by job assignment

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

Konzeptionelle Grundlagen kapazitaetsorientierter PPS-Systeme

Summary in EnglishAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel W 351 (315) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Project Scheduling under Resource and Mode Identity Constraints. Part I: Model, Complexity Status, and Methods

: A recurring problem in project management involves the allocation of scarce resources to the individual jobs comprising the project. In many situations such as audit-staff scheduling, timetabling, and course scheduling, the resources correspond to individuals (skilled labour). This naturally leads to an assignment-type project scheduling problem, i.e. a project has to be performed by assigning one or more of several individuals (resources) to each job. In this paper we consider the nonpreemptive variant of a resource-constrained project scheduling problem with mode identity. Mode identity refers to a generalization of the multi-mode case where the set of all jobs is partitioned into disjoint subsets while all jobs forming one subset have to be processed in the same mode. Both time and cost incurred by processing a subset of jobs depend on the resources assigned to it. This problem is a substantial and non-trivial generalization of the well-known multi-mode case. Regarding precedence ..

Project Scheduling under Resource and Mode Identity Constraints. Part II: An Application to Audit-Staff Scheduling

When scheduling its audit-staff, the management of an auditing firm encompasses a number of different decisions which differ markedly in terms of organizational echelon involved, length of the planning horizon and the planning periods, degree of aggregation of the audit tasks, degree of detail of the required information, and decision objective. We outline an hierarchical planning approach for the audit-staff scheduling problem and demonstrate how the first level can be expressed in terms of the MIRCPSP, which has been presented in Part I of this paper. For solving this problem, we also demonstrate how the solution approach RAMSES, also presented in Part I of this paper, can be adapted to it. We provide a number of different priority rules which can be employed alternatively