Reshape layer

[sguada]

Added a reshape layer that allows to change the shape of the blobs, although it doesn't change the size. It is generalization of flatten_layer.

[Yangqing]

Shall re rename it reshape_num, reshape_channels, reshape_height and reshape_width to avoid confusion? Since num, channels, height and width may be too general.

[sguada]

Done renamed reshape params. The new params could be used by other layers

[shelhamer]

How about reshape_ instead of new_ just to make it really obvious?

[sguada]

I did that at first, but then I thought that other layers may want to use the same parameters to specify the new dimensions of the output. See for instance #120

[jeffdonahue]

I think it's kind of redundant to have both reshape and flatten layer -- one option is to just add the extra params to FlattenLayer, change its name to ReshapeLayer, and have it default to the flattening behavior when all 0 (default) params are specified. What do you think?

Also, what is the use case for changing "num"? It seems like it may be more natural to only allow reshaping a given data instance (channels/height/width), but maybe there's a need to merge or split data instances that I'm not considering?

[sguada]

@jeffdonahue I think reshape layer could replace flatten layer if the default behavior is clear.
What about the following convention for the params
If it is 0 then it doesn't change the dimensions, that allows to specify that new_num=0 means don't change it.
And if one of the dims is -1 then it will be calculated to match the total number of elements. new_channels=-1 means create as many as needed to hold the data.

That will make the default behave as flatten layer

new_num = 0
new_channels = -1
new_height = 1
new_weight = 1

The need to change num is the motivation I created this layer, I need to be able to concatenate different images and compute features across them.

[jeffdonahue]

All makes sense and sounds good!

[shelhamer]

@sguada could you implement the flattening convention in your #108 (comment) and rebase to make this a clean merge?

Thanks!

[shelhamer]

Let's bring in #219 first, and then this can replace the flatten layer once it is a clean merge.

[shelhamer]

@sguada could you open a PR against dev instead so we can include this layer? Thanks.

[wendlerc]

When will this layer be available?

[shelhamer]

@sguada can you PR this layer to dev and include the flattening behavior in your #108 (comment)?

[shelhamer]

Replaced by #1263.