Swim operation. If the better solution is found in tumble operation, H(t, k) is updated in the generated direction, as shown in Eq 14, and continue to create bacteria until no better ones are found. H(t+1,k)=min{MSE(i)−MSEbestMSEmax−MSEminH(t,k),ME(i)−MEbestMEmax−MEminH(t,k)},(14) where MSEbest is the best MSE value found so far and MEbest is the best ME value.