反向传导算法
From Ufldl
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</math> | </math> | ||
+ | [译者注: | ||
+ | :<math> | ||
+ | \delta^{(n_l)}_i = \frac{\partial}{\partial z^{n_l}_i}J(W,b;x,y) | ||
+ | = \frac{\partial}{\partial z^{n_l}_i}\frac{1}{2} \left\|y - h_{W,b}(x)\right\|^2 | ||
+ | = \frac{\partial}{\partial z^{n_l}_i}\frac{1}{2} \sum_{j=1}^S_n_l(y_j-a_j^(n_l))^2 | ||
+ | = \frac{\partial}{\partial z^{n_l}_i}\frac{1}{2} \sum_{j=1}^S_n_l(y_j-f(z_j^(n_l)))^2 | ||
+ | = - (y_i - f(z_j^(n_l))) \cdot f'(z^{(n_l)}_i) | ||
+ | = - (y_i - a^{(n_l)}_i) \cdot f'(z^{(n_l)}_i) | ||
+ | </math> | ||
+ | ] | ||
<li>对 <math>\textstyle l = n_l-1, n_l-2, n_l-3, \ldots, 2</math> 的各个层,第 <math>\textstyle l</math> 层的第 <math>\textstyle i</math> 个节点的残差计算方法如下: | <li>对 <math>\textstyle l = n_l-1, n_l-2, n_l-3, \ldots, 2</math> 的各个层,第 <math>\textstyle l</math> 层的第 <math>\textstyle i</math> 个节点的残差计算方法如下: |