“…Due to the properties of multiobjective problems, multiple performance indices should be used to compare the performances of different methods on finding Pareto‐optimal set. In our experiments, the following performance indexes are used (Yuan et al., ; Gharaei and Jolai, ): - Size of space covered (S‐Metric): given a set of m decision vectors (), S‐Metric gives the volume enclosed by the union of the polytopes , where each P i is formed by the intersections of the following hyperplanes arising out of x i , along with the axes: for each axis in the objective space, there exists a hyperplane perpendicular to the axis and passing through its objective value. Here, since the LWTC model we presented above is a minimization problem, we choose the largest objective values among the results obtained by all methods in 20 trials as the reference point (i.e., largest tardiness, largest costs).
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