1 A survey and
This thesis has made the following contributions.
1 A survey and analysis of diversity in genetic programming demonstrated the complexity behind the issue of diversity measures and methods and the relationship between diversity and fitness.
2 An analysis using genetic lineages showed how a search metaphor of hill-climbing can be used to explain and improve genetic programming search. Also, the sampling of unique structures and behaviours demonstrated the the low sampling of both complex behaviours and unique structures of large size.
3 A causal model was developed which linked increased rates of code growth to non-decreased selection pressure and to increased similarity within the population. Decreased selection pressure occurs when fitness-based diversity is lost, and increased similarity in the population is the result of both faster convergence and non-decreased selection pressure.
4 An analysis using the Tree-String problem showed the inability to produce good offspring by both dissimilar-and-fit individuals and by similar-and-equally-well-fit individuals.
5 A model was proposed that identifies dissimilar individuals and moves them to new islands where they can contribute to search more effectively.
S Gustafson 2004-05-20