Re: [Vala] Further speculations on couroutines, generators and threads : Emulating Go's goroutines and channels in Vala

[Alexandre Rosenfeld <alexandre rosenfeld gmail com>]

On Wed, Jul 13, 2011 at 15:17, august <august alien mur at> wrote:

>        "With asynchronous methods it is possible to do programming without
>        any blocking."
>
> The following examples in the tutorial  are much more enlightening...so
> it's not that bad.   But, maybe it could be improved.

Async methods were created primarily for GIO to do non-blocking IO. Doing IO
usually blocks the application and so freezes the UI, so the GLib answer is
to provide callbacks to be called when the IO is done and the program can
keep executing while IO is done in the background (note here that background
does not necessarily mean another thread, the IO can be done by the kernel
and notify the process when it's complete).


> I always thought async methods:
>        a) are always single threaded
>        b) uses the glib runtime scheduler to simulate
>                multi-processes
>        c) cannot take advantage of multi-core or multi-processor
>                computers

Async methods have nothing to do with threads, so none of these points are
valid. However, what async methods allow is to stop the processing of a
function in the middle and resume it after the async method returns, by the
means of the callbacks. So, what the async method can do is spawn a thread
to do background processing and later call the callback to resume the
operation of the method that called it.
Which means async methods can be just as blocking as any other method if it
does sequential processing and at the end calls the callback. But also means
it can be designed to use any other way to provide background processing
(including threads) without blocking the main program (especially the UI)
and thus can take advantage of multiple cores.

At least this is what I understood so far about async methods, please let me
know if any of this is wrong.

Regards,
Alexandre