Which direction: DifferentiatonInterface, Enzyme, Zygote with CUDA and FFTs?

[giordano]

Autodifferentiation with FFT, with Enzyme?

It would be great to have some Enzyme rules in AbstractFFTs.jl (there’s a draft PR at Add EnzymeRules by sethaxen · Pull Request #103 · JuliaMath/AbstractFFTs.jl · GitHub, but someone has to adopt the project and get it over the finish line). In the meantime, maybe you’ll find the following Enzyme reverse rule useful, extracted from a private project I’m working on. It’s not a complete solution (no forward rules, no batched rules, no rule for mul!), but I think it’s correct for the cases it cov…