Comparing and combining lexicase selection and novelty search

Abstract

Lexicase selection and novelty search, two parent selection methods used in evolutionary computation, emphasize exploring widely in the search space more than traditional methods such as tournament selection. However, lexicase selection is not explicitly driven to select for novelty in the population, and novelty search suffers from lack of direction toward a goal, especially in unconstrained, highly-dimensional spaces. We combine the strengths of lexicase selection and novelty search by creating a novelty score for each test case, and adding those novelty scores to the normal error values used in lexicase selection. We use this new novelty-lexicase selection to solve automatic program synthesis problems, and find it significantly outperforms both novelty search and lexicase selection. Additionally, we find that novelty search has very little success in the problem domain of program synthesis. We explore the effects of each of these methods on population diversity and long-term problem solving performance, and give evidence to support the hypothesis that novelty-lexicase selection resists converging to local optima better than lexicase selection.

Recent Developments in Program Synthesis with Evolutionary Algorithms

“…Using PushGP, lexicase selection variants have been in recent work often compared to other selection methods (e.g., tournament selection) and achieved best success rates on many program synthesis benchmark problems [16], [29], [46], [47], [48], [49], [50], [51], [52], [53], [45].…”

“…Replace Space with Newline [16], [29], [46], [82], [47], [74], [48], [39], [75], [36], [83], [50], [51], [81], [84], [15], [76], [52], [40], [42], [80], [45], [85], [54], [38], [77], [49] [12], [63], [54] -30…”

“…Last Index of Zero [16], [29], [74], [48], [39], [75], [50], [51], [76], [52], [40], [53], [42], [41], [80], [45], [38] [11], [61], [12], [2], [63], [72] [72] 24…”

“…Negative to Zero [16], [29], [46], [82], [47], [74], [48], [39], [75], [36], [50], [51], [76], [52], [40], [42], [80], [45], [54], [38], [77] [11], [12], [2], [63], [54], [72] [72] 28…”

“…Scrabble Score [16], [29], [74], [48], [39], [75], [51], [76], [52], [40], [42], [80], [45], [38] [61], [12], [63] -17…”