Figure 4: A total of 40 runs of 100 generations each for each function and each method were performed. The population size is 56 for GA, PSO, and HPSO, respectively, and the number of subpopulation is 4 for HPSO. The relative mean square error between the estimated solutions and real solutions is calculated for each trial. Table 1 shows the averaged relative mean square error over 40 trials for each method. Flowchart of HPSO.