Experiments on networks of employee timetabling problems

Amnon Meisels, Natalia Lusternik

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

16 Scopus citations


The natural representation of employee timetabling problems (ETPs), as constraint networks (CNs), has variables representing tasks and values representing employees that are assigned to tasks. In this representation, ETPs have binary constraints of non-equality (mutual exclusion), the networks are non uniform, and variables have different domains of values. There is also a typical family of non-binary constraints that represent finite capacity limits. These features differentiate the networks of ETPs from random uniform binary CNs. Much experimental work has been done in recent years on random binary constraint networks (cf. [10, 11, 9]) and the so called phase transitions have been connected with certain value combinations of the parameters of random binary CNs. This paper designs and experiments with a random testbed of ETPs that includes all of the above features and is solved by standard constraint processing techniques, such as forward checking (FC) and conflict directed backjumping (CBJ). Random ETPs are characterized by the usual parameters of constraint networks, like the density of constraints Pl. One result of the experiments is that random ETPs exhibit a strong change in difficulty, as measured by consistency checks, (a phase transition). The critical parameter for the observed phase transition is the average size of domains of variables. Non binary constraints of finite capacity are part of the experimental testbed. An enhanced FC-CBJ search algorithm is used to test these random networks and the experimental results are presented.

Original languageEnglish
Title of host publicationPractice and Theory of Automated Timetabling II - 2nd International Conference, PATAT 1997, Selected Papers
EditorsEdmund Burke, Michael Carter
PublisherSpringer Verlag
Number of pages12
ISBN (Print)3540649794, 9783540649793
StatePublished - 1998
Externally publishedYes
Event2nd International Conference on Practice and Theory of Automated Timetabling, PATAT 1997 - Toronto, Canada
Duration: 20 Aug 199722 Aug 1997

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference2nd International Conference on Practice and Theory of Automated Timetabling, PATAT 1997

Bibliographical note

Publisher Copyright:
© Springer-Verlag Berlin Heidelberg 1998.


  • Constraint networks
  • Employee timetabling
  • Experimental CSP
  • Non binary constraints


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