反向传导算法

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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>

Revision as of 16:59, 7 March 2013

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