[ChrisRackauckas]

Not necessarily: you can use it to build fast inverse of scalar functions. Here's an example on a vjp of an ODE f:

https://gist.github.com/GiggleLiu/0c4608f70bda050f59992f5fc0...

[cbkeller]

I'm probably just missing something, but did you mean to say "fast derivatives of scalar functions" by any chance? I.e., that you can use the free inverses to get at the derivatives in some way?

[ChrisRackauckas]

oh yes, I meant derivatives.