Hypervolume measures the volume dominated by the Pareto front and bounded by a reference point. The value of hypervolume can increase or stay equal as the Pareto front improves. As shown in Figure , qNEHVI gave similar hypervolume performance compared to TSEMO (Figure ) but a significant reduction in computational time (average time per iteration of qNEHVI: 5.1 s vs. average time of TSEMO: 121.5 s) was achieved (Figure ). The reason for the improvement of calculation time is because TSEMO uses a multi-objective genetic algorithm (NSGA-II), while qNEHVI uses a second-order gradient algorithm (L-BFGS-B) with random restarts. The latter is generally significantly faster, especially with the categorical variables where we used the rounding trick. Therefore, we use qNEHVI to optimise the Schotten-Baumann reaction.