“…In the comparison, 17 algorithms are implemented and tested on Matlab 2015b, all based on the well-known k-NN classifier with k = 5. To show the performance of the proposed algorithm, we compare it with the standard GA, the original CSO algorithm [25], the original PSO, DE [32], ABC-DE [34], ACO-FS [31], ACO-ABC [33], GSA [56], BQIGSA [57], four variants of PSO proposed by Xue's for bi-objective feature subset selection [36] (Xue1-PSO, Xue2-PSO, Xue3-PSO, and Xue4-PSO), and three two-stage algorithms include 2S-GA [40], 2S-HGA [41], and 2S-PSO [39]. Based on Xue et al [36], the major difference between Xue's algorithms is the number of features selected in the initial swarm, while Xue1-PSO uses the normal initialization method where approximately half of the features are chosen in each particles, Xue2-PSO applies a little initialization method in which only about 10% features are chosen in each particles, Xue3-PSO applies heavy initialization method in which more than half (about 2/3) of the features are chosen in each particles, and Xue4-PSO applies a combined initialization in which a major (about 2/3) of the particles are initialized with the little initialization method, while the remaining particles of swarm are initialized with the heavy initialization method.…”