Authors:
Allan de Lima
1
;
Samuel Carvalho
2
;
Douglas Dias
1
;
Joseph Sullivan
2
and
Conor Ryan
1
Affiliations:
1
University of Limerick, Limerick, Ireland
;
2
Technological University of the Shannon: Midlands Midwest, Limerick, Ireland
Keyword(s):
Lexicase, Tournament, Bloat.
Abstract:
We proposed a novel and simple selection system that alternates between tournament and Lexicase selection to tackle the bloat issue. In this way, we used Lexi2 , an implementation of Lexicase with lexicographic parsimony pressure, adopting the number of nodes in our solutions as size measurement. In addition, we increased the parsimony pressure by adding a penalty, also based on the number of nodes, to the aggregated fitness score. We analysed different scenarios, including some without extra parameters, in five benchmark problems: 2-bit Multiplier, 5-bit Parity, Car Evaluation, LED and Heart Disease. We succeeded in all of them in at least one scenario, reducing the size significantly while maintaining fitness. Beyond error and size, we also included results for the average number of fitness cases used in each generation.