[Freeciv-Dev] Re: [RFC][Patch] Inline

[Jason Short <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

Raahul Kumar wrote:

> I was requesting those numbers. It seems -03 is a fairly bad optimisation. 
> Jason ran some tests on the stock freeciv, and he seemed to get large increases
> in performance just by using NDEBUG. Jason, some comments on your previous
> tests please?
>
> With your patch and NDEBUG the speed increase is minor. Why?
Short answer: he gets these gains already in the patch.

When NDEBUG is defined, CHECK_MAP_POS is defined out and so is never 
called.  CHECK_MAP_POS just calls is_normal_map_pos, which calls 
normalize_map_pos.  Both of these are functions, so there is a 
substantial overhead to calling them [1].  This is the largest source of 
the difference between NDEBUG and !NDEBUG, though there are of course 
other assertions in there as well.
Raimar's patch seems to disable CHECK_MAP_POS entirely (which is not 
unreasonable, BTW...one plan was to change CHECK_MAP_POS to only be used 
if DEBUG was defined before the release), so he'll get these benefits 
without NDEBUG.  Even without this, though, is_normal_map_pos and 
normalize_map_pos are functions that should be inlined (currently only 
normalize_map_pos is AFAICT), so the overhead would be less in any case.
[1] Before anyone clamours for their removal: they have helped in 
tracking down a number of bugs and will probably help to track down many 
more.
jason