Combating user fatigue and contradictions in subjective-based optimization schemes

Xavier Llorā


ABSTRACT: One of the daunting challenges of interactive genetic algorithms (iGAs)genetic algorithms in which fitness measure of a solution is provided by a human rather than by a fitness function, model, or computation—is user fatigue which leads to sub-optimal solutions. This talk presents a method to combat user fatigue by augmenting user evaluations with a synthetic fitness function. The proposed method combines partial ordering concepts, notion of non-domination from multiobjective optimization, and support vector machines to synthesize a fitness model based on user evaluation. The proposed method is used in an iGA on a simple test problem and the results demonstrate that the method actively combats user fatigue by requiring 3–7 times less user evaluation when compared to a simple iGA. Moreover, the explicit use of partial ordering concepts leads any contradictory evaluation provided by the user introduces to be identified as a cycle in the graph. This property is explored to create measures of the consistency of the evaluations provided by the user along the evolutionary process.

Xavier Llorā interest and work on genetics-based machine learning (GBML) have earned him a spot among
the leaders of the renaissance of learning classifier systems (LCSs). His 2002 PhD dissertation
challenged traditional data-mining techniques by showing the effectiveness of GBML approaches.
He is currently editing a forthcoming book on Advances at the Frontiers of Learning Classifier Systems
(Llorā, Kovacs, & Takadama, Summer 2006) that will review recent work in the field.
He has served recently as LCS/GBML track chair in the ACM SIGEVO organized GECCO conference.
Llorā, awarded with a young research fellowship by the Catalan Government, started his academic career
at the Ramon Llull University (Barcelona, Spain) where he earned his PhD degree with honors.
In 2003 he moved to the University of Illinois at Urbana-Champaign where he joined the
Illinois Genetic Algorithms Laboratory. Since then, Llorā has leaded the DISCUS project
(, a project to support collaborative human-innovation and creativity;
the National Center for Supercomputing Applications and several national and Japanese universities
and consortiums are project partners. In summer 2005, Llorā was named research assistant professor
at the University of Illinois at Urbana-Champaign.

Deepak Ramachandran
Last modified: Fri Aug 8 11:38:17 CST 2006