反向传导算法
From Ufldl
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[译者注:由于原作者简化了推导过程,会影响理解,我将推导过程补全为以下公式: | [译者注:由于原作者简化了推导过程,会影响理解,我将推导过程补全为以下公式: | ||
:<math> | :<math> | ||
- | \delta^{(n_l)}_i = \frac{\partial}{partial z^{n_l}_i}J(W,b;x,y) | + | \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} \left\|y - h_{W,b}(x)\right\|^2 |
= - (y_i - a^{(n_l)}_i) \cdot f'(z^{(n_l)}_i) | = - (y_i - a^{(n_l)}_i) \cdot f'(z^{(n_l)}_i) | ||
</math> | </math> |