CGAL users discussion list

[Andreas Fabri <>]

Hi Alejandro,

Cartesian has reference counted objects. You might try Simple_cartesian 
instead.

Best regards,

andreas



Alejandro Aragon wrote:
> By the way, talking about points in CGAL. I decided to create my own 
> point class, templated by the dimension of the point to see the 
> difference in creation time with that of the CGAL types. I introduced an 
> implicit conversion so that I can use my point type where a CGAL 
> algorithm needs it. Then my test was just creating points. It was 
> surprising the time that it took the creation of 10e9 Point_2 objects 
> compared to my simple templated point class:
>
> int main(int argc, char *argv[]) {
>
>     typedef CGAL::Point_2 PointType;
>
>     Timer t1;
>     cout<<"CGAL point"<<endl;
>     t1.Reset();
>     for (long i=0; i<1.0e9; ++i) {
>         PointType p(3,5);
>     }
>     t1.Tac();
>     cout<<"my point"<<endl;
>     t1.Reset();
>     for (long i=0; i<1.0e9; ++i) {
>         geometry::Point<2> p(3,5);
>     }
>     t1.Tac();
>
>     exit(0);
> }
>
> $./a.out
> CGAL point
> Time: 74.2738sec
> Measurement granularity: 1000000 of a second
> my point
> Time: 1.57362sec
> Measurement granularity: 1000000 of a second
>
> so can someone tell me why is this? I would never expect an almost 
> factor of 50 in execution times! and this was just for creating a point.
>
> Alejandro M. Aragón
>
>
> On Jul 23, 2008, at 10:48 AM, Andreas Fabri wrote:
>
> > Sylvain Pion wrote:
> > > Alejandro Aragon a écrit :
> > > > Hi, no one has replied to my post yet, so I decided to send it again 
> > > > in case someone will.
> > > Wrong decision : you should have decided to read the FAQ, for example.
> >
> > http://www.cgal.org/FAQ.html#inexact_NT
> >
> > > > I'm trying to check how the oriented_side() function works for a 
> > > > line. I
> > > > created a very simple example, where a point should lie on a line, 
> > > > but it
> > > > doesn't. The program is as follows:
> > > >
> > > > #include <CGAL/Cartesian.h>
> > > > #include <iostream>
> > > >
> > > > using std::cout;
> > > > using std::endl;
> > > >
> > > > int main() {
> > > >
> > > > typedef CGAL::Cartesian<double> KernelType;
> > > > typedef KernelType::Point_2 PointType;
> > > > typedef KernelType::Line_2 LineType;
> > > >
> > > >
> > > > PointType p(0.034,0.006);
> > > > cout<<"point -> "<<p<<endl;
> > > >
> > > > LineType l(-0.004, 0.004, 0.000112);
> > > > cout<<"line -> "<<l<<endl;
> > > >
> > > > CGAL::Oriented_side test = l.oriented_side(p);
> > > >
> > > > if ( test == CGAL::ON_POSITIVE_SIDE ) {
> > > > cout<<"point on positive side"<<endl;
> > > > } else if ( test == CGAL::ON_NEGATIVE_SIDE ) {
> > > > cout<<"point on negative side"<<endl;
> > > > } else {
> > > > cout<<"point over line"<<endl;
> > > > }
> > > >
> > > > return 0;
> > > > }
> > > >
> > > > The output of this little program is:
> > > >
> > > > point -> 0.034 0.006
> > > > line -> -0.004 0.004 0.000112
> > > > point on negative side
> > > >
> > > > Can someone tell me what is happening here? The point should not be 
> > > > on the
> > > > negative side. Thank you all.
> >
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