None of the models in the intermediate-cost group is on the Pareto front for both the training set and the validation set. M 3,3 yields the lowest RMSE of 0.07 eV for the training set, however its performance deteriorates considerably for the validation set with an RMSE of 0.22 eV. The next best model for the training set, M 2,3 , with an RMSE of 0.09 eV also performs significantly worse for the validation set with an RMSE of 0.19 eV. We therefore choose the third model, M 3,2 , because its RMSE of 0.09 eV for the training set is similar to M 2,3 , but its performance for the validation set is markedly better with an RMSE of 0.17 eV.