Error: The number of filter groups does not divide the total number of filters.

Matcovnet 遇到了这个错误，查了资料才知道是filter的channel数目不对，查看手册发现：

VL_NNCONV

 - CNN convolution.

Y = VL_NNCONV(X, F, B) computes the convolution of the image X with the filter bank F and biases B. If B is the empty matrix, then no biases are added. If F is the empty matrix, then the function does not filter the image, but still adds the biases and applies
downsampling and padding as explained below.

X is an array of dimension H x W x C x N where (H,W) are the height and width of the image stack, C is the number of feature channels, and N is the number of images in the batch.

F is an array of dimension FW x FH x FC x K where (FH,FW) are the filter height and width and K the number o filters in the bank. FC is the number of feature channels in each filter and must match the number of feature channels C in X. Alternatively,
FC can
divide* the C; in this case, filters are assumed to form G=C/FC

groups* of equal size (where G must divide K). Each group of

filters works on a consecutive subset of feature channels of the input array X.

黑色的是重点，要求FC与C关系，不然会报错。

这个提问，可以参考下。
https://github.com/vlfeat/matconvnet/issues/222
Hi, your data has 384 channels, and your filters only one channel. This means that there are 384 filter groups, one for each channel, and each containing one filter. If this is your intention, you should have 384 filters, each of which will act independently
on a corresponding input dimension (note that working with many small groups is not implemented very efficiently in the library).

However, I think you meant to create filters with 384 dimensions instead. If this is the case the filters should be 

randn(7,7,384,50,
'single’)

.

On 29 Jul 2015, at 11:16, Kevin Chen notifications@github.com wrote:
Hi, guys. In my implementation, the first layer was displayed for error using : the number of filter groups does not divide the total number of filters. So I wondered why I got this error message. Can anyone help
me out? Thanks a lot.
% layer 1: convolution

net.layers{end+1} = struct('type', 'conv', ...

'filters', f*randn(7,7,1,50, 'single'), ...

'biases', zeros(1, 50,'single'), ...

'stride', 1, ...
'pad', 0) ;
l.filters =
7 7 1 50

l.biases =
1 50

res(i).x =

.
32 32 384 100
Error using vl_nnconv

The number of filter groups does not divide the total number of filters.
Error in vl_simplenn (line 156)

res(i+1).x = vl_nnconv(res(i).x, l.filters, l.biases, 'pad', l.pad, 'stride', l.stride) ;
Error in cnn_train (line 141)

res = vl_simplenn(net, im, one, res, ...
Error in cnn_LIVEII (line 93)

[net,info] = cnn_train(net, imdb, @getbatch, ... % "net" with above-defined layers
—

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