Because the extreme point of the energy function E ( W)( W)( W is weight vector) is equal to zero point of the gradient, tracking the energy function extreme point can be converted into tracking its gradient function zero point. 因为能量函数E(W)(W是权重矢量)的极值点相当于梯度wE(W)的零点,因此,对能量函数极值点的跟踪可以转化为对其梯度函数零点的跟踪。