> There is also the option of combining both. Then we do not get the
> regression, but still the improvement for fft2:

I *definitely* think we should leave Call Arity in place by default unless and until something strictly better comes along. One very nice feature is that it works for a lot of user-written code of various kinds without the user having to do *anything* special. oneShot seems more limited in applicability, for use primarily in library code. So I would personally think that it should be added, with an option, of course, to turn it off. I would also go for documenting it as experimental and provisional.

David