反向传导算法
From Ufldl
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&= \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-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 \\ | = \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( | + | &= - (y_i - f(z_i^{(n_l)})) \cdot f'(z^{(n_l)}_i) |
= - (y_i - a^{(n_l)}_i) \cdot f'(z^{(n_l)}_i) | = - (y_i - a^{(n_l)}_i) \cdot f'(z^{(n_l)}_i) | ||
\end{align} | \end{align} | ||
