Speeding up Local Search for the Indicator-based Subset Selection Problem by a Candidate List Strategy

In evolutionary multi-objective optimization, the indicator-based subset selection problem involves finding a subset of points that maximizes a given quality indicator. Local search is an effective approach for obtaining a high-quality subset in this problem. However, local search requires high computational cost, especially as the size of the point set and the number of objectives increase. To address this issue, this paper proposes a candidate list strategy for local search in the indicator-based subset selection problem. In the proposed strategy, each point in a given point set has a candidate list. During search, each point is only eligible to swap with unselected points in its associated candidate list. This restriction drastically reduces the number of swaps at each iteration of local search. We consider two types of candidate lists: nearest neighbor and random neighbor lists. This paper investigates the effectiveness of the proposed candidate list strategy on various Pareto fronts. The results show that the proposed strategy with the nearest neighbor list can significantly speed up local search on continuous Pareto fronts without significantly compromising the subset quality. The results also show that the sequential use of the two lists can address the discontinuity of Pareto fronts.