Preface: 21st International Conference on Applications of Evolutionary Computation - Sim, Kevin; Kaufmann, Paul; Ascheid, Gerd; Bacardit, Jaume; Cagnoni, Stefano; Cotta, Carlos; D’Andreagiovanni, Fabio; Divina, Federico; Esparcia-Alcázar, Anna I.; Vega, Francisco Fernández De; Glette, Kyrre; Hubert, Julien; et al. (My University, 2018)