Why in search-gumbel-architect.py-def _backward_step_unrolled(), dalpha is []?

[zhou123123123]

hi, thank you for your research,I read your paper and code, and i fing in your paper in formula 17, you gradient alpha. But in your code,dalpha=[]. can you tell me the reason? thanks.

[latstars]

Gradient updates in this line (https://github.com/VDIGPKU/DADA/blob/master/search_gumbel/architect.py#L66).