Doubt about Gradient

[gtbai]

https://github.com/gtbai/DistributedFFM/blob/9bd5c97dacf1f44929b2aa052b830b4b22f12732/src/ffm.py#L75

1. Maybe calc g_j1_f2 and g_j2_f1 seperately?
2. How to apply when weights appear more than once?