Deformable Convolutional Networks V2 with Pytorch

    .\make  # build
    python test.py # run gradient check 

Known issues:

-[ ] Gradient check w.r.t offset. -[ ] Backward is not reentrant.

This is adaption of the official Deformable-ConvNets. I have ran the gradient check for many times with DOUBLE type. Every tensor except offset passes. However, when I set the offset to 0.5, it passes. I'm still wondering what cause this problem. Is it because some non-differential points?

Another issue is that it raises RuntimeError: Backward is not reentrant. However, the error is very small (<1e-7), so it may not be a serious problem (?)

Please post an issue or PR if you have any comments.