CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 10/06/2013 09:11 PM, Stefan Salewski wrote:
> On Sun, 2013-10-06 at 17:11 +0200, Stefan Salewski wrote:
> > I guess it may be
> > problematic due to rounding -- I may use two doubles to create a site
> > and as keys of my hash entry, but may get back a rounded double value
> > due to CGAL's intern exact arithmetic?
>
> Or in other words:
>
> double x = 3.14; // double constant
> p = Point(x, x);
> s = Site(p, 2);
> h = ag.insert(s);
> Point pp = h->site().point();
> double xx = CGAL::to_double(pp.x());
> assert(xx != x);
>
> I think the assert() is never executed, because CGAL::to_double() always
> returns the exact initial value?
>
> I still wonder how serious arithmetic errors are for apollonius graphs?
> May I get small errors when I would use plain double data type, or may
> the whole graph generation fail?
The whole generation might fail.
See also http://www.cgal.org/FAQ.html#inexact_NT

Sebastien.

> Best regards,
>
> Stefan Salewski