Need Diffractor.jl for State-of-the-Art Deep Learning Model

[ChrisRackauckas]

@1115

I can see some tests about higher order AD in Diffractor, it is a good proof of its effort in optimzing compiling. Just wondering what is the typical using case of higher order reverse mode AD?

There is a use case for 2 reverse passes (but not more, the rest forward) in some applications of physics-informed neural networks, and so you can see PINNs as the test case. Fun fact, Diffractor.jl was grant funded for these weird SciML applications (same ARPA-E that made ModelingToolkit.jl, Symbolics.jl, and JuliaSim), but of course fast higher order AD is something anyone could benefit from.