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Expand file tree Collapse file tree Original file line number Diff line number Diff line change 180180 - ![ $$ {{\rm{n}}_i} $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7B%7B%5Crm%7Bn%7D%7D_i%7D%24%24 ) ………………………………..第i层神经元个数
181181 - W………………………………权重
182182 - Cost………………………………代价函数
183- - 所以第` i+1 ` 层的输入：
183+ - 所以第` i+1 ` 层的输入：
184184![ $$ {{\rm{s}}^i} = {z^i}{W^i} + {b^i} $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7B%7B%5Crm%7Bs%7D%7D%5Ei%7D%20%3D%20%7Bz%5Ei%7D%7BW%5Ei%7D%20&plus ; %20%7Bb%5Ei%7D%24%24 )
185- - ![ $$ {z^{i + 1}} = f({s^i}) $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7Bz%5E%7Bi%20&plus ; %201%7D%7D%20%3D%20f%28%7Bs%5Ei%7D%29%24%24 ) ，即` z ` 对应激活之后的值
186- - 根据BP反向传播可以得到：![ $$ {{\partial Cost} \over {\partial s_k^i}} = {f^'}(s_k^i)W_{k, \bullet }^{i + 1}{{\partial Cost} \over {\partial {s^{i + 1}}}} $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7B%7B%5Cpartial%20Cost%7D%20%5Cover%20%7B%5Cpartial%20s_k%5Ei%7D%7D%20%3D%20%7Bf%5E%27%7D%28s_k%5Ei%29W_%7Bk%2C%20%5Cbullet%20%7D%5E%7Bi%20&plus ; %201%7D%7B%7B%5Cpartial%20Cost%7D%20%5Cover%20%7B%5Cpartial%20%7Bs%5E%7Bi%20&plus ; %201%7D%7D%7D%7D%24%24 )
185+ - 激活之后的值表示：
186+ ![ $$ {z^{i + 1}} = f({s^i}) $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7Bz%5E%7Bi%20&plus ; %201%7D%7D%20%3D%20f%28%7Bs%5Ei%7D%29%24%24 ) ，
187+ - 根据BP反向传播可以得到：
188+ ![ $$ {{\partial Cost} \over {\partial s_k^i}} = {f^'}(s_k^i)W_{k, \bullet }^{i + 1}{{\partial Cost} \over {\partial {s^{i + 1}}}} $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7B%7B%5Cpartial%20Cost%7D%20%5Cover%20%7B%5Cpartial%20s_k%5Ei%7D%7D%20%3D%20%7Bf%5E%27%7D%28s_k%5Ei%29W_%7Bk%2C%20%5Cbullet%20%7D%5E%7Bi%20&plus ; %201%7D%7B%7B%5Cpartial%20Cost%7D%20%5Cover%20%7B%5Cpartial%20%7Bs%5E%7Bi%20&plus ; %201%7D%7D%7D%7D%24%24 )
187189 - 权重的偏导（梯度）就为：![ $$ {{\partial Cost} \over {\partial w_{l,k}^i}} = z_l^i{{\partial Cost} \over {\partial s_k^i}} $$ ] ( http://latex.codecogs.com/gif.latex?%5Clarge%20%24%24%7B%7B%5Cpartial%20Cost%7D%20%5Cover%20%7B%5Cpartial%20w_%7Bl%2Ck%7D%5Ei%7D%7D%20%3D%20z_l%5Ei%7B%7B%5Cpartial%20Cost%7D%20%5Cover%20%7B%5Cpartial%20s_k%5Ei%7D%7D%24%24 )
188190 - 还是BP反向传播的推导，可以查看我之前给的BP反向传播的推导。
189191 - 它这里` W ` 是从` 0 ` 开始的，所以对应可能不太一致。
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