CGAL users discussion list

[Maarten Moesen <>]

Hello Stephen and Peter,

> I agree with you when you mention that that section in the manual can be 
> overlooked.  
> Perhaps a separate heading with "Kernel Selection" can provide more insight 
> to the user.
Although I'm aware that kernels and their efficiency are prone to
changes, I too think it is a good suggestion to make a separate section
about kernel selection. Why not opening it up to requirements,
limitations and recommendations for kernels and add also what's
mentioned in the reference guide. This may save a user lots of time!

Regards and keep up the good work,

Maarten

> 
> Yes, I have used NDEBUG and O2.
> 
> Stephen
> 
> -----Original Message-----
> From: Peter Hachenberger 
> [mailto:]
> Sent: February-22-08 11:39 AM
> To: 
> 
> Subject: RE: [cgal-discuss] [3d_boolean_ops] Most Efficient Rational Kernel
> 
> Hi Stephen,
> 
> I introduced these new items, because it was clear that filtered kernels
> are inefficient with the old ones. The new ones allow efficient
> filtering. Since I mostly wanted to speed up Cartesian kernels and
> therefore allow handling of double coordinates, I write about it at a
> seemingly strange place of the documentation. It's in the user manual
> under File I/O.
> 
> BTW, do you compile with -DNDEBUG and -O2? That usually gives a big
> efficiency boost.
> 
> Peter
> 
> On Fri, 2008-02-22 at 11:19 -0800, Stephen Wong wrote:
> > Hi Peter,
> >
> > I didn't use SNC_indexed_items before.  I am noticing about 30-40% 
> > improvement in computation time (30% faster) after using 
> > Exact_constructions_exact_predicates and SNC_indexed_items!
> >
> > What does the indexed items do?  It's not mentioned in the documentation 
> > - in fact, the current documentation suggests that you should stay with 
> > the default, SNC_items.
> >
> > Thanks for your excellent analysis.
> >
> > Stephen
> >
> > -----Original Message-----
> > From: Peter Hachenberger 
> > [mailto:]
> > Sent: February-22-08 4:14 AM
> > To: 
> > 
> > Subject: Re: [cgal-discuss] [3d_boolean_ops] Most Efficient Rational 
> > Kernel
> >
> > Hi Stephen,
> >
> > I performed some tests. Assuming you have gmp but no leda, the
> > Exact_predicate_exact_constructions_kernel is up to double as fast as
> > all the others. Don't forget to use the SNC_indexed_items with that
> > kernel. Also all the other kernels (besides the extended kernels) profit
> > from the SNC_indexed_items. The second fastest seems to be
> > Simple_cartesian<Gmpq>. The homogeneous kernels were in general slower
> > than the Cartesians. That would be different with LEDA.
> > Homogeneous<leda_integer> is very fast.
> >
> > Peter
> >
> > On Mon, 2008-02-18 at 11:38 -0800, Stephen Wong wrote:
> > > Hi there,
> > >
> > >
> > >
> > > I am wondering what is the most computationally-efficient kernel that
> > > is allowable in Nef Polyhedra in 3D (Boolean operations), in the set
> > > of rational numbers Q.  Right now I am using Cartesian<Gmpq>, a
> > > variant of Exact_predicate_exact_constructions_kernel.  I am wondering
> > > if there is a Kernel (than I have stated) that performs more
> > > efficiently.  If not, is there a more efficient number type than Gmpq
> > > that is compatible with 3D Nef Polyhedra?
> > >
> > >
> > >
> > > On the same topic of discussion, if I were to use kernels representing
> > > Z, which is the most efficient kernel?
> > >
> > >
> > >
> > > Thanks,
> > >
> > >
> > >
> > > Stephen
> > >
> > >
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> >
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-- 
ir. Maarten Moesen
Department of Metallurgy and Materials Engineering (MTM)
K.U.Leuven
Kasteelpark Arenberg 44 - Bus 02450
B-3001 Heverlee, Belgium
tel. +32 (0)16 32 13 17
fax. +32 (0)16 32 19 90


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