CGAL users discussion list

["Thomas Zangl - Home" <>]

Am Thu, 03 Jul 2008 15:21:43 +0200, schrieb "Andreas Fabri" 
<>:

Hi!

Another question which arise during testing:

in ftp://ftp-sop.inria.fr/geometrica/pion/publis/lazy-kernel.pdf you
make a comparison between different kernels. Now, I ask myself:

if I use:
typedef CGAL::Simple_cartesian<CGAL::Gmpq> K;
typedef CGAL::Gmpq dbl;

all predicates and operations are done exactly? Like if the
filter of the Filtered_Kernel always returns "NO_IDEA"? 

The reason is, if I use the plain Exact_pred_exact_constr. kernel, my
test app does not produce any degenerate cases. If I use the kernel
typedef'd above, I get a lot of them. It seems, computation accuracy is
far worse with the Simple_cartesian<CGAL::Gmpq> in my case.

Any idea why this can happen? How can I clarify that all computations
are done using exact arithmetic like described in your paper? 

TIA,
-- 
,yours Thomas Zangl, Bakk.rer.soc.oec. - 

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