REAL

Hammock Activities in Project Scheduling

Csébfalvi, Anikó Borbála and Csébfalvi, György (2005) Hammock Activities in Project Scheduling. In: Proceedings of the Sixteenth Annual Conference of POMS, 2005.04.29-2005.05.02, Chicago IL.

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Abstract

The concept of hammock activities plays a central role in project management. They are used to fill the time span between other "normal" activities since their duration cannot be calculated or estimated at the initial stage of project planning. However, the recent literature does not offer a general and useful method to compute the unconstrained (resource constrained) duration of such activities. In the proposed approach, a hammock activity is characterized by two dummy activities; therefore the estimation of the unconstrained hammock duration can be formulated as a simple linear programming (LP) problem. The resource-constrained hammock activity duration computation can be described as a mixed integer linear programming (MILP) problem with big- M constraints, which can be solved directly for small-scale projects in reasonable time. The presented implicit enumeration algorithm for the resource constrained hammock activity duration is formulated as a tree-search problem with effective pruning rules. The first pruning rule is based on a special consistency check, which can help to visibilize the "invisible" inconsistencies. The second pruning rule eliminates schedules from explicit enumeration that are known to be unnecessary. The third pruning rule is based on the relaxation of a MILP model, which is a tighter reformulation of the traditional zero-one resource constrained project scheduling model. According to the NP-hard nature of the problem, the proposed implicit enumeration algorithm provides exact solutions for small to medium size problems in reasonable time. Large-scale problems can be managed by introducing an optimality tolerance. In order to illustrate the essence and viability of the proposed new approach, we present detailed computational results for a simple example.

Item Type: Conference or Workshop Item (Paper)
Additional Information: MTMT: 1269770 DOI: 10.4203/ccp.102.160 In.: Shrikant Panwalkar, Jian Li (szerk.): Proceedings of the Sixteenth Annual Conference of POMS. 2005. Konferencia helye, ideje: Chicago IL, Amerikai Egyesült Államok, 2005.04.29.-2005.05.02.
Subjects: T Technology / alkalmazott, műszaki tudományok > T2 Technology (General) / műszaki tudományok általában
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 06 Jun 2014 08:02
Last Modified: 12 Jun 2014 13:23
URI: http://real.mtak.hu/id/eprint/13032

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