How to realize U-net without nngraph, can it use nn.ConcatTable() to realize it ?

[royal-feng]

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Because some operation is difficult to define in nngraph，I want to make an nn.sequential to realize U-net network architecture? what about use the nn.ConcatTable() to do it ? Anybody have some cool idea?

[dmarnerides]

I've implemented U-net using only nn. You can have a look here. Let me know if there are any problems with it.