“…For example, the evaluation of the constraint functions may be time-consuming, and consequently, surrogates need to be built for constraints [29], [45], [46]. Since constraints can be handled using penalty functions [47], surrogates are built to approximate the penalty function instead of the individual constraint functions [48], [49]. As whether a candidate solution is feasible or not can be seen as a classification problem, support vector machine [50], [51], k-nearest neighbors algorithm [52], and linear hyper-plane estimator [53] have been employed to distinguish feasible solutions from infeasible ones.…”