CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

Le vendredi 17 août 2012 15:54:46 Marc Glisse a écrit :
> On Thu, 26 Jul 2012, Marc Mörig wrote:
> > Dear CGAL maintainers,
> > 
> > in CORE_Expr.h there is twice the call
> > 
> > x.approx(53,1024);
> > 
> > meant to improve the internal approximation in x to double quality.
> > After a call x.approx(r,a) the internal approximation z is such that
> > 
> > |x - z| <= max{ |x|2^{-r}, 2^{-a}  }
> > 
> > So that call wastes precision if x is in the underflow range. It should be
> > 
> > x.approx(53,1075);
> > 
> > since the smallest (positive nonzero) double is 2^{-1074}.
> 
> Thank you for the detailed report. It makes sense, I have made the
> suggested change for 4.2.

CGAL 4.2 will be released in January 2013. If the fix is harmless, I can 
backport it to CGAL 4.1, that will be released in September 2012.

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/