[geos-devel] Upgrading to geos 3.3.0 broke all our codebase !

[Sandro Santilli]

On Fri, Jul 08, 2011 at 01:23:05PM +0200, Maxime van Noppen wrote:

> We care a lot about performance. In specific intensive loops this
> might add 0.1 to 3% (wild guess based on previous profiling of the
> code) of overhead. 

[...]

> A very-very-simple-and-naive test to have some feedback:

[...]

> int main()
> {
> 
>   geos::geom::GeometryFactory gf;
>   std::list<geos::geom::Point*> point_list;
> 
>   geos::geom::Coordinate c;
>   c.x = 0;
>   c.y = 0;
>   geos::geom::Geometry* p = gf.createPoint(c);
> 
>   for (unsigned int i = 0; i < 100000; ++i)
>     point_list.push_back(dynamic_cast<geos::geom::Point*>(p));
> 
>   std::cout << point_list.size() << std::endl;
> }
> ---------------------------------------------------------------
> 
> Compiled with g++ -03, this yields these results:
> 
>  - main() : 100%
>     - dynamic_cast    : 41%
>     - operator new    : 31.6%
>     - operator delete : 15.2%
> 
> This enlightens the cost of dynamic_cast which can really be a big
> hit on such specific and intensive loops.

You're basically noticing here that about 17 calls to malloc + 17 
calls to free (34 calls of memory related functions) are taking up
41 + 15.2 = 56.2% of the time while 41% of it is spent doing 100000
dynamic_cast calls.

And this is assuming you sampled enough time to be meaningful...

I guess your average GEOS application does more than that ?

--strk; 

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