Updated Reshape layer

[ssafar]

Here is a layer similar to sguada's #108. Main differences:

• like FlattenLayer, it doesn't copy blobs
• has numpy-like "-1 for automatic dimension inference" and uses the default 0 to copy dimensions from below (just like it was planned in Reshape layer #108)
• is using the latest API.

As for unifying FlattenLayer and this one, also discussed in #108: technically it could be doable but they have really different defaults. For ReshapeLayer, they are 0 0 0 0 (that is, don't change any dimensions unless explicitly requested), while for a FlattenLayer-like default behavior, we'd need 0 -1 1 1 ("keep num, infer channels, flatten everything else). Also, it might be confusing to have something called RESHAPE automatically flatten things or FLATTEN with parameters doing something entirely different from flattening. Or at least that was my reasoning behind creating another layer; it might still be wrong :)

Also, sorry if it's already work in progress by someone; I was looking at the dates on #108, concluded that I'd like to use such a thing most likely sooner than its expected arrival time, and that it might be useful if I posted it if I was going to implement it for myself anyway. Let me know if this wasn't really the right way of doing things :)

[shelhamer]

Thanks for resurrecting ReshapeLayer! It looks like there are a few issues to work out but this is a good start.

@sguada please review and merge.

[Yangqing]

No action required, but FYI: I am going to change the layer_factory code so that all REGISTER_LAYER_CLASS commands go to their corresponding .cc files, instead of all inside layer_factory.cpp.

[longjon]

@Yangqing good, I had meant to ask about that some time ago...

[Yangqing]

#1270 materializes this plan - all you need to do is to move the

REGISTER_LAYER_CLASS(RESHAPE, ReshapeLayer);

line to reshape_layer.cpp under the INSTANTIATE_CLASS line. Hope this does not cause much trouble.

[ssafar]

Done! (It indeed didn't :))

[shelhamer]

Please squash into a single commit with an informative message for merge. Thanks for the layer!

[ssafar]

Done! Also added some docs to the layer catalog about how to use it.

[shelhamer]

This looks good to me but needs a master edition. @ssafar if you have a chance that's ideal, or else we could merge to master from this PR at some point.

[jeffdonahue]

rebased in #2217

[ssafar]

@jeffdonahue: thanks for the rebase & fixing it up! (& sorry for not doing it myself & disappearing for so long, I had neither a proper GPU-equipped box nor time lately. But then it's all good in the end :))