Internal and external iteration, fibers

[deadalnix]

On Monday, 21 January 2013 at 20:15:49 UTC, Rob T wrote:
> On Monday, 21 January 2013 at 08:44:10 UTC, Nick Sabalausky 
> wrote:
>>> I ask, because if except for the overhead, fibers are a good 
>>> general solution, then it makes sense to determine if 
>>> anything can be done to lessen the overhead before trying to 
>>> implement yet another solution.
>>> 
>>
>> Yea, they *would* be a good general solution, and I'm sure the 
>> overhead
>> can be decreased, but AIUI I don't think it's even 
>> theoretically
>> possible for them to optimized enough to compete with any of 
>> the other
>> approaches as a general-purpose thing.
>>
>> The other stuff can be optimized down as far as being little 
>> more than
>> an increment per iteration. But AIUI, using a real fiber would 
>> require
>> two context-switches per iteration, so I'm not sure that can 
>> ever
>> compete.
>
> I have not yet had time to actually use fibers for anything 
> real, but I did play around with them and the usage seemed to 
> be exactly what we're looking for to implement co-routines. 
> Since you have experience using them for real, do you think 
> they are useful in general assuming that the performance can be 
> made par with the stackless select switch method?
>

It has no chance to be as fast. However, I use them quite a lot 
and they are very useful. Especially to hide IO latency or for 
dependancy management. I use them for the latter, some other 
software (like vide.d) use them for the former.

This cannot be achieved with stackless coroutine method as you 
need to yield from anywhere, not only the root function.

> By chance, do you know if the current implementation is a 
> built-in language feature or if it's implemented entirely as a 
> library?
>

This is done as library right now, which is awesome !