CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

Le mercredi 20 octobre 2010 15:07:03, Sebastian Kapfer a écrit :
> Dear Sebastien!
> 
> On Wed, Oct 20, 2010 at 11:27:26AM +0200, Sebastien Loriot 
> (GeometryFactory) 
wrote:
> > I can see you have a 64bits machine. Mine is 32.
> > I try on a 64bits machine and still you code ran without
> > assertion failure.
> > 
> > Did you used cmake to build CGAL?
> 
> Yes.
> 
> > can you try using cmake to generate the makefile to compile
> > your example (you can use the script cgal_create_cmake_script to
> > generate a CMakeLists.txt)
> 
> Using CMake has nothing to do with it.

You are wrong. With gcc-4.2, for example, CGAL cmake scripts adds the 
compilation flag -fno-strict-aliasing, because the aliasing features of that 
version of gcc have bugs.

> In the meantime, I tried on a more modern machine. Ubuntu Lucid, GCC
> 4.4, AMD64, Boost 1.43, CGAL 3.7.  Same problem.
> 
> But your mention of your 32 bit machine tripped me off.  Of course, on
> AMD64, GCC uses the SSE unit to implement floating point, which has
> 64-bit floats all the way through, and doesn't use 80-bit floats for
> registers.
> 
> > sk@noether(~/spielwiese/fast_thicken/MinimalExample)>
> >  g++ -O3
> > -frounding-math -mfpmath=387 -lCGAL -odistance_browsing
> > distance_browsing.cpp
> > sk@noether(~/spielwiese/fast_thicken/MinimalExample)>
> > ./distance_browsing
> > sk@noether(~/spielwiese/fast_thicken/MinimalExample)>
> >  g++ -O3
> > -frounding-math -mfpmath=sse -lCGAL -odistance_browsing
> > distance_browsing.cpp
> > sk@noether(~/spielwiese/fast_thicken/MinimalExample)>
> > ./distance_browsing
> > terminate called after throwing an instance of
> > 'CGAL::Assertion_exception'
> > 
> >   what():  CGAL ERROR: assertion violation!
> >   Expr: new_rd >= copy_rd
> >   File:
> >   /opt/cgal/3.7_boost1.40/include/CGAL/Orthogonal_incremental_neighbor_se
> >   arch.h Line: 267
> >   Aborted
> 
> (see http://gcc.gnu.org/onlinedocs/gcc/i386-and-x86_002d64-Options.html)
> 
> So it seems CGAL works when using 80-bit floats, but not with true
> 64-bit floats?

No. CGAL is tested on different platforms, including of course 32 and 64 bits 
one. The error comes probably from something else. You compiled your programs 
without using CMake. What header <CGAL/compiler_config.h> is found when g++ 
is 
called without -I flags? Does this header correspond to the same version of 
CGAL as the libCGAL.so that is found by the linker without -L flags? It seems 
your CGAL installation is in /opt/cgal/3.7_boost1.40/. How comes that your 
compiler can found its headers and library without -I and -L flags?

-- 
Laurent Rineau, PhD
Release Manager of the CGAL Project       http://www.cgal.org/
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/