Performance difference between optional args and keyword args

[Henrique_Becker]

@ericphanson

My understanding is Julia still specializes on keyword arguments although it does not dispatch on them.

This is correct but keyword arguments until recently had some limitations that made the compiler infer worse what is related, see: Add keyword argument constant propogation to News by ChrisRackauckas · Pull Request #36292 · JuliaLang/julia · GitHub

@ericphanson

But I think generally speaking they shouldn’t be slower than positional arguments.

I am not sure of that. If I remember correctly, there was a kw_sorter generic function that had to be called receiving the NamedTuple arguments to fill in the defaults and then pass to the under-the-hood method that has no keyword arguments (only positional ones). I think that for larger lists of keyword parameters in which some of them are explicit and other are missing, the function may take a performance hit (but if the function makes any considerable effort this ends up being a little overhead).