Archiver Effects on the Performance of State-of-the-art Multi and Many-objective Evolutionary Algorithms

Early works on external solution archiving have pointed out the benefits of unbounded archivers and there have been great advances, theoretical and algorithmic, in bounded archiving methods. Moreover, recent work has shown that the populations of most multi- and many-objective evolutionary algorithms (MOEAs) lack the properties that one would desire when trying to find a bounded Pareto-optimal front. Despite all these results, many recent MOEAs are still being proposed, analyzed and compared without considering any kind of archiver assuming their additional computational cost is not justified. In this paper, we investigate the effect of using various kinds of archivers, improving over previous studies in several aspects: (i) the parameters of MOEAs with and without an external archiver are tuned separately using automatic configuration methods; (ii) we consider a comprehensive range of problem scenarios (number of objectives, function evaluations, computation time limit); (iii) we employ multiple, complementary quality metrics; and (iv) we study the effect of unbounded archivers and two state-of-the-art bounded archiving methods. Our results show that both unbounded and bounded archivers are beneficial even for many-objective problems. We conclude that future proposals and comparisons of MOEAs must include archiving as an algorithmic component.