Shame. On the upside, it’s all perf wins optimizin...

# announcements

[pakoito]

Shame. On the upside, it’s all perf wins optimizing code from there 😄

[karelpeeters]

What allocation is this about?

[pakoito]

https://github.com/arrow-kt/arrow/pull/1332#discussion_r263609089

[pakoito]

this one

[pakoito]

it’s not a biggie by itself, it just makes me wonder whether to audit the codebase for others

[karelpeeters]

I'm still pretty lost, are you talking about repeated uses if the same code as a lambda or something like that?

[pakoito]

So IO could be doing one extra allocation per mapFilter call, which isn’t too much of an issue

[pakoito]

at scale, if every call to every IO through the codebase adds an allocation or a couple, they could add up to something meaningful

[pakoito]

not something that’ll get you to UI jank on an Android app but you know, something noticeable that’s just free perf

[raulraja]

I think what Paco means that if the compiler finds this expression map { f(it) } could optimice it to just map(f) not incurring in an additional lambda allocation.

[pakoito]

^^^^^ that

[raulraja]

unless it already does that which I don't know.

[karelpeeters]

Oh where f is another lambda/function parameter. I was thinking of it as a real function 🤦‍♂️

[raulraja]

no it's just whatever map or any function for that matter takes as argument

[raulraja]

applying it to it seems to have a cost where it's obvious it could be optimized to just pass the reference to the method

[raulraja]

I'm not sure if JIT or Kotlin already tries to optimize these cases, so also looking forward to finding out

[Dico]

What allocation though? As in it puts an extra variable on the stack? What?? If I got this right, I'd say this investigation is a waste of your time. No offense.

[Dico]

Unless map is called on a Sequence in which case it's not inlined of course.

[dmcg]

I'm a bit confused. I suppose that most maps are inline, in which case it's moot, but in this case the particular map wasn't?

[pakoito]

we have plenty of non-inlined maps in arrow because they're suspended constructs

[pakoito]

maps for list, map, set, and other collections are eager and it could make sense to inline them if you're not concerned about bycode bloat

[pakoito]

maps for observable, IO, even mapping functions themselves require capturing the lambda parameter in a data structure to execute it later

[pakoito]

so you do pay for that extra allocation