After selection, a population of new parents is formed, $yk\u2032\u2032$, $k=1,\u2026,\mu $; then the strategy parameters $\sigma newk,p$ of each new parent created from the mutation operator are updated by means of a deterministic adjustment, called the 1/5-success rule, which says that if the estimated probability of successful mutation is $>1/5$, $\sigma newk,p$ is increased; otherwise, it is decreased, that is, ^{11}^{–}^{13}Display Formula
$If[fitness(ymutatedk\u2032\u2032)>fitness(yselectedk)]>1/5$
Display Formula$\sigma updatedk,p=\sigma newk,p*(1+d),p=1,\u2026\u2026,35.$
Else Display Formula$\sigma updatedk,p=\sigma newk,p/d,p=1,\u2026\u2026,35,$
where $d$ is a small positive constant. For all numerical experiments, we used $d=0.001$. Furthermore, $yselectedk$ represents the corresponding randomly selected individual from the initial population to be mutated.