CGAL users discussion list

Thanks a lot for your answer!!
But I have many problems with CGAL::Gmpq type... I use few mathematic
functions like sqrt() or acos() from "math.h" package...
Are they defined for CGAL::Gmpq type? and where?


> 
>  wrote:
>> I work with the CGAL library to compute a bounded voronoi diagram for
>> my academic research project. I use the Delaunay_triangulation_2 class,
>> the Voronoi_diagram_2 class, the Min_sphere_of_spheres_d class et other
>> functions like "intersection".
>>
>> I would like to write an article about my subject but I need to know
>> the computing precision. I use C++ double type and I would like to know
>> what is the precision that CGAL can ensure? I work with real number (in
>> double) in the interval [0,1], so how many figures after the comma
>> without precision's error can I publish?
>
> I'm assuming that you speak about the coordinates of the vertices,
> say, of the computed Voronoi diagram.
>
> If your programs exclusively work with type double, and no exact
> fallback number types (like CGAL::Gmpq or CGAL::MP_Float) are being used,
> then CGAL cannot give you any strict precision guarantees. The programs
> may even fail completely for certain inputs.
>
> However, if you compute exactly (this is possible by various means
> in CGAL) and only round the computed results to double in the end, you
> typically incur only unit roundoff, i.e. the results are correct to around
> 17 decimal digits. See http://www.cgal.org/philosophy.html
> for more on the exact computing paradigm in CGAL.
>
> Best,
> Bernd.
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