Speed of vectorized vs for-loops using Zygote

[ChrisRackauckas]

@roflmaostc

Zygote fails completely (in terms of performance) on the for-loop function. The vectorized is ok.
But Zygote is roughly 5-10x slower than the function itself.

That’s expected with the current Zygote. I would swap out to ReverseDiff.jl with tape compilation if you’re doing a lot of scalar computations.