随机逼近，一种不需求导的求最优值或特定值的逼近算法。基本方法为设目标值为A,要找这样的x,使h(x)=A。-Stochastic approximation .without　derivation, a　kind of approximation algorithm of optimal value or particular value.Basic method for setting the target for A, want to find such x, h (x) = A.