Re: gtk+ speed

[Alberto Garcia <agarcia igalia com>]

On Mon, Dec 22, 2008 at 02:44:40PM +0000, Ross Burton wrote:

> > the code generated for a virtual function in C++ is as far as I
> > understand (as I said, noob here) in principle the same as the
> > code you have to manually write in GObject to do the same thing,
> > it's just much more invisible.
> 
> Exactly.  C++ can do slightly more optimisation because the OO,
> casting and so on are in the compiler instead of built at runtime,
> but the underlying mechanics are the same.

As you say, because type casts are dinamic, there's the overhead of
calling g_type_check_instance_* which in languages like C++ is not
needed because it's done at compilation time. I suspect that this
overhead is negligible (I haven't made real tests, though).

However, there is a performance problem with private attributes
(if you use g_type_class_add_private()) that don't exist in other
languages, as GObject's g_type_instance_get_private() can be
noticeably slow.

There are ways of overcoming this problem, fortunately. More info
here:

http://arbur.net/serendipity/archives/40-g_type_instance_get_private-performance-costs.html

http://www.gnome.org/~federico/news-2006-01.html#24

-- 
Alberto García González
http://people.igalia.com/berto/