is the mean acceptance probability at iteration i and σ i is the corresponding standard deviation. For an optimal balance of the P acc (k), the final value of σ i should be as small as possible. According to Eq. 4, the differences ∆s i+1 k are corrected by a factor that is strictly proportional to the product of the standard deviation σ i and the difference between the actual value of P acc (k) i and the mean acceptance ratio. As the sum of the differences, n-1 k