vedaldi
commented
9 years ago Hi, that’s because the convolution applied spatially, but not done across feature channels. This is in principle possible, but it would amount to account for “channel” as a third coordinate analogous to space, which would be odd. For example, there is usually no preferential order in features (although this rule is not always true: there is in local cross-channel normalisation).
On 17 Mar 2015, at 05:11, Zhiyang Wang notifications@github.com wrote:
Hi! Very glad to be the first person starting an issue!
I am a new learner to CNNs and recently I found some problem when reading the MatConvNet documentation or VGG Convolutional Neural Networks Practical.
In Part 1.1 of the practical there is a question "Note that x is indexed by i+i′ and j+j′, but that there is no plus sign between k and k′. Why?" This is also my question.
(1) In that formula, why does $x$ has four dimensions but $f$ has only three dimensions? When defining x,y and f we found clearly that x and y are 3-dimensional, f is 4-dimensional. (2) Why do the first two dimensions of $x$ are i+i′ and j+j′? Does that mean that (row-1, col-1) of x is not involved in the convolution process? If so, I don't think it is right.
— Reply to this email directly or view it on GitHub https://github.com/vedaldi/practical-cnn/issues/1.
slmjlf
in the VGG practical or
in the manual of MatConvNet.
The right form should be
geumjandi
Hi! Very glad to be the first person starting an issue!
I am a new learner to CNNs and recently I found some problem when reading the MatConvNet documentation or VGG Convolutional Neural Networks Practical.
In Part 1.1 of the practical there is a question "Note that x is indexed by i+i′ and j+j′, but that there is no plus sign between k and k′. Why?" This is also my question.
(1) In that formula, why does x has four dimensions but f has only three dimensions? When defining x,y and f we found clearly that x and y are 3-dimensional, f is 4-dimensional. Is there any typo in this formula? (2) Why do the first two dimensions of x are i+i′ and j+j′? Does that mean that (row-1, col-1) of x is not involved in the convolution process? If so, I don't think it is right.