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A comment on Differentiation for Hackers. Parent comment

Re:Differentiation for Hackers by gugagore on Saturday June 22, 2019 @02:49PM (#20251075)
I don't think this is right. An autodiff package will likely report +inf for the derivative of cuberoot at 0.

The problem is really that there are a lot of ways the function can have infinite slope. The sqrt function also has infinite slope at 0.

Dividing by zero isn't where the NaN comes from.

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Re:Differentiation for Hackers by tobmlt on Saturday June 22, 2019 @04:46PM (#20251647)
My mistake then. I did not intend to try and be so precise. I was thinking loosely. I have a very simple autodiff tool hand rolled (in Python) here to play with. I raise 0 to a negative exponent in the gradient of the cube root at 0. I do not get a NAN. Strictly speaking I get this:

"ZeroDivisionError: 0.0 cannot be raised to a negative power"

Is that satisfying? I do not claim anything more specific here. Sorry to be imprecise.

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