RuntimeError: start (0) + length (0) exceeds dimension size (0)

Probably due to your tensor shape, there is a narrow on empty tensor some where. You can try use a debugger and/or print out the tensor shapes to see where things got wrong.

Additionally, we have added proper empty tensor support, and will be available in next release. So the error message will be nicer. But that probably isn’t the root of your problem.