Why stackless (async/await) for Swift?

[Jon_Shier]

True. I may try some of the other, faster implementations to see how they compare.

[Jon_Shier]

Erlang non-HIPE runs in as little as 721ms.
Go in as little as 454ms.
Pony in as little as 254ms.
LuaJIT in as little as 144ms.

I tried a bunch more but the examples are too out of date for modern versions of their tools.

[tera]

Great, thank you! Swift looks the fastest.

Are you getting a faster result if you change from actor to class in the swift implementation?

[tera]

@AlexanderM

TL;DR: Implementing async/await as sugar over Promises like in JS or Python just leads to a linked list of promises. It's a very simple and straightforward implementation with fantastic backwards compatibility, but it's a pain train of heap allocations and indirection (which is marginally cost in itself, but it prohibits a lot of other optimizations). Coroutine based async/await is much more complicated to implement (but luckily that's done already, great work team!), but better in every other way I can think of.

Not that winning a popularity contest means it's necessarily better, but it's worth noting that C#, Rust and Go have all gone with some flavour of coroutine (stackful or stackless) as their backing primitive for async/await.

Thank you Alexander, I'm quoting you here as it is more appropriate to have it here rather in the topic named "The Swift Postmortem".

Anyone here aware of a good benchmark (or a set of benchmarks) to compare different approaches in this space? I tried the mentioned skynet benchmark but it only touches a fraction of the relevant surface area.