Exercise:Convolution and Pooling
From Ufldl
(→Step 3a: Convolution) |
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These same three steps must also be applied to the convolved patches. | These same three steps must also be applied to the convolved patches. | ||
- | Taking the preprocessing steps into account, the feature activations that you should compute is <math>\sigma(W(T(x-\bar{x})) + b)</math>, where <math>T</math> is the whitening matrix and <math>\bar | + | Taking the preprocessing steps into account, the feature activations that you should compute is <math>\sigma(W(T(x-\bar{x})) + b)</math>, where <math>T</math> is the whitening matrix and <math>\bar{x}</math> is the mean patch. Expanding this, you obtain <math>\sigma(WTx - WT\bar{x} + b)</math>, which suggests that you should convolve the images with <math>WT</math> rather than <math>W</math> as earlier, and you should add <math>(b - WT\bar{x})</math>, rather than just <math>b</math> to the resulting matrix <tt>C</tt>, before finally applying the sigmoid function. |
==== Step 3b: Checking ==== | ==== Step 3b: Checking ==== |