Complexity Measures for Multi-objective Symbolic Regression
This work addresses the selection of complexity measures in symbolic regression for researchers in evolutionary computation, though it is incremental as it builds on existing multi-objective optimization methods.
The study investigated which complexity measures are most effective for multi-objective symbolic regression using NSGA-II, introducing a novel semantic-based measure and testing it on benchmark datasets to analyze trade-offs between accuracy and model length.
Multi-objective symbolic regression has the advantage that while the accuracy of the learned models is maximized, the complexity is automatically adapted and need not be specified a-priori. The result of the optimization is not a single solution anymore, but a whole Pareto-front describing the trade-off between accuracy and complexity. In this contribution we study which complexity measures are most appropriately used in symbolic regression when performing multi- objective optimization with NSGA-II. Furthermore, we present a novel complexity measure that includes semantic information based on the function symbols occurring in the models and test its effects on several benchmark datasets. Results comparing multiple complexity measures are presented in terms of the achieved accuracy and model length to illustrate how the search direction of the algorithm is affected.