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- From: Andreas Fabri <>
- To:
- Subject: Re: [cgal-discuss] point lying over a line problem
- Date: Wed, 23 Jul 2008 18:25:37 +0200
tolerant algorithms are difficult to implement correctly.
Imagine you do 1D geometry, and decide that points (numbers)
are equal if they only differ on the 15th digit.
Imagine a < b < c in the mathematical sense, and positioned
in a way that a ~ b and b ~ c, but a !~ c then your algorithms
on top of the equality test of points must be written with
the assumption that your equality test is not transitive.
andreas
Alejandro Aragon wrote:
Thanks for replying, I actually read the FAQ before posting my message and I understand that the double type is inexact. However, I don't see why the need of using an "exact" number type when algorithms can be modified such that they give exact results within tolerance. If a double precision type is exact up to the 15th digit, then algorithms should take that into account so when I try to intersect that point with the line, the point is supposed to lie over the line within let's say tol = 10e-14.
Why would I use an exact number type? I don't want to do that, it will slow down a program that I'm actually trying to speed up by doing some profiling.
Alejandro M. Aragón
On Jul 23, 2008, at 10:42 AM, Olivier Devillers wrote:
Alejandro Aragon a écrit :
typedef CGAL::Cartesian<double> KernelType;
If you compute with double, rounding errors make your points non collinear
(e.g. during the decimal to binary conversion if your input is given by
floating point number in decimal notation)
http://www.cgal.org/FAQ.html#inexact_NT
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- Re: [cgal-discuss] point lying over a line problem, (continued)
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Fernando Cacciola, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Andreas Fabri, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Olivier Devillers, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Olivier Devillers, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Fernando Cacciola, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Andreas Fabri, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Sylvain Pion, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
- Re: [cgal-discuss] point lying over a line problem, Alejandro Aragon, 07/23/2008
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