How can I check if the gradients follow to certain variables

[roastduck]

Hi,

I am porting a renderer to use Enzyme, but Enzyme outputs the gradients to be 0 on CUDA (it is correct on CPU). I think there is something that Enzyme consider as non-differentiable but actually differentiable. I think one way to diagnose this issue could be to verify if each intermediate variables are receiving gradients. Is there a simple method to accomplish this, except for returning all of them from the function?