[ylow]

Some random historical notes coroutine stuff which are perhaps of interest to some:

1. You can implement "stack-free coroutines" in C with some really entertaining macros https://www.chiark.greenend.org.uk/~sgtatham/coroutines.html

2. Does anyone remembers Cilk? Its still the fastest stackful coroutine models I know of.

Having implemented and used both before (for different purposes), I like both, but with a mild preference for the stackful version. Largely because you don't have function coloring problems, and you can actually get a proper stack trace and is so significantly easier to debug when things go wrong.

It is also good to differentiate coroutines from async (they seem to be very interleaved these days). Coroutines are a mechanic to achieve mutual recursion / generators. And that is fine for expressing certain algorithms and systems in a much cleaner fashion. Note that parallelism is not necessarily implied by "coroutine".

Async is a mechanic to "doing something else" while waiting for IO. Fibers or state machines are both different solutions to this problem. Certain coroutine implementations can help with this, but I think it is massively overused. Rust due to the function coloring problem, ends up requiring almost everything to be marked "async". And some golang code I have read seems to overuse goroutines unecessarily. I think use of async should be narrow and minimized, and localized to only the places where it makes sense.

[gpderetta]

> Does anyone remembers Cilk?

Yes! It's a shame it never gained traction and Intel abandoned it, eventually getting dropped from icc and gcc.