CGAL users discussion list

[Gilbert Bernstein <>]

Peter,

I just tried DNDEBUG and it reduced the time to convert the cat from  
off to nef down to ~30 seconds, which seems like it should make sense.

So, as the next entry in the never ending story, I just tried to  
perform the shark union with a much  higher polycount shark model and  
discovered the following error upon trying to convert the result back  
from nef to off:

CGAL error: precondition violation!
Expr: it1.e_ == it2.e_
File: /usr/local/include/CGAL/iterator.h
Line: 563
Explanation:
terminate called after throwing an instance of  
'CGAL::Precondition_exception'
  what():  CGAL ERROR: precondition violation!
Expr: it1.e_ == it2.e_
File: /usr/local/include/CGAL/iterator.h
Line: 563

I'm using the following header consistently across all conversion  
programs and the set operations file:

#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Polyhedron_3.h>
#include <CGAL/IO/Polyhedron_iostream.h>
#include <CGAL/Nef_polyhedron_3.h>
#include <CGAL/Nef_3/SNC_indexed_items.h>
#include <CGAL/IO/Nef_polyhedron_iostream_3.h>

typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef CGAL::Polyhedron_3<Kernel>  Polyhedron;
typedef CGAL::SNC_indexed_items Items;
typedef CGAL::Nef_polyhedron_3<Kernel, Items>  Nef_polyhedron;

Sorry 'bout this.

-- Gilbert

On Jan 9, 2008, at 4:43 AM, Peter Hachenberger wrote:

Hi Gilbert,

I'm glad that I could help you. It's interesting to know that Gmp and
mpfr make such a difference.

Did you also add the option -DNDEBUG? This might again give you 20-40
seconds.

Peter

On Tue, 2008-01-08 at 23:55 -0600, Gilbert Bernstein wrote:
> Sorry about spamming the list so much here.
>
> Peter,
>
>         It seems the problem was the lack of gmp and mpfr. (from what I
> understand they're mutually dependent inside of CGAL) After
> installing those and rebuilding CGAL, all my programs worked
> correctly without changing the code at all.
>
> It takes me 80 seconds to convert robocat with -O2 set and using the
> exact_predicates_exact_constructions kernel.  This seems at least
> within the realm of plausibility now.  Do you have any
> recommendations on trying to bring this number down closer to 20
> seconds?  Perhaps a particular Kernel is very well suited?
>
> -- Gilbert
>
>
> On Jan 8, 2008, at 6:03 AM, Peter Hachenberger wrote:
>
> So, the robocat took less than 20 seconds on my notebook, which has 2
> Ghz with only one Core. So, taking also your other mail into  
> accout, it
> seems that your CGAL installation might miss some important data types
> and is therefore slower than necessary. Maybe the code I gave you  
> in the
> previous mail will not compile, because you don't have Gmp or some
> similar problem.
>
> Peter
>
> On Mon, 2008-01-07 at 13:46 -0600, Gilbert Bernstein wrote:
> > Peter,
> >
> > Here is the robocat (3756 vert 7512 tri) model, which I was able to
> > get through in half an hour.  I was running another job along with
> > it, so it may not take that long, though it should take a good while.
> >
> > I also tried a simplified shark model (1007 vert 2010 tri) which I
> > just measured at appx. 2 min to convert on my 1.83 Ghz Core Duo (not
> > Core2) (using only one core I believe)
> >
> > -- Gilbert
> >
> > On Jan 7, 2008, at 6:11 AM, Peter Hachenberger wrote:
> >
> > Hi Gilbert,
> >
> > half an hour is more than I would expect from a model of that size. I
> > have an example file that has about 2/3 of the size of your model and
> > the execution of  handling_double_coordinates takes less than half a
> > minute. So, I'm a bit surprised. Can you please send me the file so
> > that
> > I can test it.
> >
> > Peter
> >
> > On Mon, 2008-01-07 at 03:47 -0600, Gilbert Bernstein wrote:
> > > It seems I have to apologize for making such a stink here.  It was
> > > probably a false alarm.
> > >
> > > I think I had unreasonable expectations on the speed of the
> > > computation and thought the program had gone into a loop.  I managed
> > > to push a smaller model (3756 vertices 7512 triangles) through the
> > > conversion both ways just now by waiting about half an hour.  I also
> > > know the model in question has some very funky joins between parts
> > > (lots of long, close, sharp polygons) so I'm pretty sure this was
> > > just a matter of patience.  If only I was testing with the teapot.
> > > Then I could make a really awful joke about watched teapots.
> > >
> > > I just ran another model (1007 vert 2010 tri) through just fine,  
> > > much
> > > faster, so yeah...
> > >
> > > -- Gilbert
> > >
> > > On Jan 7, 2008, at 3:12 AM, Andreas Fabri wrote:
> > >
> > >
> > > Gilbert,
> > >
> > > It might be the best to just post a file that makes problems.
> > > What is your OS/compiler, did you just take the example or
> > > demo program, or write your own program? In the latter case
> > > what kernel did you chooses?
> > >
> > > andreas
> > >
> > >
> > > Gilbert Bernstein wrote:
> > > > Andreas,
> > > >     I'm fairly sure all of the meshes I've tried are triangular
> > > > meshes, (I went back and checked a couple of them (since they're in
> > > > ascii) by eye) so I don't think that's the problem.
> > > > -- Gilbert
> > > > On Jan 7, 2008, at 2:10 AM, Andreas Fabri wrote:
> > > > Hello,
> > > > A typical problem is to have faces which are not triangular,
> > > > and at the same time not coplanar.
> > > > andreas
> > > > Gilbert Bernstein wrote:
> > > > > Hi,
> > > > >     I'm having an awful lot of trouble successfully building Nef
> > > > > Polyhedra from .off input files.  The only model I have
> > > > > successfully translated from .off to a Nef Polyhedron and back is
> > > > > a cube.  I have tried a number of different models, all supposed
> > > > > to be watertight, and which were certified by the
> > > > > Polyhedron_3::is_closed() function.  It certainly may be the case
> > > > > that there was something off (ba dum chh) about these models, but
> > > > > I've reached my point of frustration.  If anyone has any known
> > > > > working examples of importing models into the Nef Polyhedron type,
> > > > > or any suggestions, I would much appreciate the tips.
> > > > > -- Gilbert Bernstein
> > > --
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