Python class as loss layer in Caffe.

An example showing how to use Python class as loss Layer in Caffe.

Code mainly comes from https://gist.github.com//shelhamer/8d9a94cf75e6fb2df221#file-pyloss-py-L28

Conclusion of callback sequence:

initialization:

1. => setup()
2. => reshape()

training:

1. => reshape()
2. => forward()
3. => backward()

notice:

remember to put pyloss.py in $PYTHONPATH, or just copy it to $CAFFE_HOME/python for convenience(make sure you had added it to $PYTHONPATH).