All benchmark function experiments were performed with a total population size of 50 and a maximum iteration number of 10000. If the difference between fitness and target value was less than 1 × 10 -8 , the calculation was considered converged. An ensemble of 100 search runs was generated to enhance the statistical significance of the result. For all CPSO calculations, the parameters γ = 1, φ p = φ g = 1.49618, and ω = 0.7298 were used. A mutation constant of F = 0.5 and a crossover constant of CR = 0.9 were taken in the case of the DE algorithm. The 'best1bin' differential evolution strategy (compare with Eq. ( )) was applied, following