CGAL users discussion list

[Sylvain Pion <>]

Thomas Zangl - Home a écrit :
>  
> Am Sun, 8 Jun 2008 13:06:53 +0200, schrieb "Thomas Zangl - Home" <>:
>
> Hi all!
>
> I wrote the mail below on 8th June and did not receive any reply. Maybe
> someone can comment on it? This would *greatly* help. Thank you!

Sorry, your mail was on my stack, but I got not much time to process it.

> > I want to use CGAL´s Delaunay Triangulation inside multiple threads
> > where each thread can run on a different CPU. I use boost::thread and the
> > threadpool from threadpool.sf.net. 
> >
> > What do I need to obey if I want to use CGAL with multiple threads? How
> > threadsafe are the triangulatione etc.? 

As Laurent said, for CGAL 3.3, not much.  We hope to have something better
for 3.4 though (at least for Delaunay_3).

In 3.3, you cannot insert/remove in parallel, even in disconnected areas, 
since
the underlying container is not thread-safe.  You should be able to iterate
over the vertices/faces in parallel though.  You can dereference existing
handles in parallel as well.

> > I get various signal 11 errors when I e.g. ask for the dual of a Delaunay
> > Triangulation face and so on. Errors like this:
> > *** glibc detected *** corrupted double-linked list: 0x0d1f81b8 ***
> >
> > Core dump says:
> > #0  0x0819dbac in _int_malloc ()
> > #1  0x0819f7e6 in malloc ()
> > #2  0x08172af8 in operator new ()
> > #3  0x080d3e04 in CGAL::Lazy_construction<CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, 
> > CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::To_interval<CGAL::Gmpq> > >, CGAL::CommonKernelFunctors::Construct_segment_3<CGAL::Simple_cartesian<CGAL::Interval_nt<false> > >, 
> > CGAL::CommonKernelFunctors::Construct_segment_3<CGAL::Simple_cartesian<CGAL::Gmpq> > >::operator()<CGAL::Point_3<CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, 
> > CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::To_interval<CGAL::Gmpq> > > >, CGAL::Point_3<CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, 
> > CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<f
al
>  s
> > e> >, CGAL::To_interval<CGAL::Gmpq> > > > > ()
> > #4  0x080d7cb6 in CGAL::DT3<CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, 
> > CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::To_interval<CGAL::Gmpq> > >, CGAL::TDS3<CGAL::TH_vb3<CGAL::Triangulation_vertex_base_with_info_3<boost::shared_ptr<Isp>, CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, 
> > CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::To_interval<CGAL::Gmpq> > >, 
> > CGAL::T_vb3<CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, 
> > CGAL::To_interval<CGAL::Gmpq> > >, CGAL::TDS_vb3<void> > > >, CGAL::Triangulation_cell_base_with_info_3<boost::shared_ptr<DCellProp
er
>  t
> > y>, CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, 
> > CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::To_interval<CGAL::Gmpq> > >, CGAL::T_cb3<CGAL::Lazy_kernel<CGAL::Simple_cartesian<CGAL::Gmpq>, 
> > CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, CGAL::Cartesian_converter<CGAL::Simple_cartesian<CGAL::Gmpq>, CGAL::Simple_cartesian<CGAL::Interval_nt<false> >, 
> > CGAL::To_interval<CGAL::Gmpq> > >, CGAL::TDS_cb3<void> > > > >::dual ()
> > #5  0x080cafd0 in DFacetProperty::setDual ()
> > #6  0x080d9143 in DCellProperty::insertFacets ()
> > #7  0x080dd258 in CComponent::dtriangulate ()
> > #8  0x080ddafa in CComponent::doWork ()
> > #9  0x0805d4bc in boost::function0<void, std::allocator<boost::function_base> 
> > >::operator() ()
> > #10 0x0805d955 in 
> > boost::threadpool::detail::worker_thread<boost::threadpool::detail::pool_core<boost::function0<void,
> >  std::allocator<boost::function_base> >, boost::threadpool::fifo_scheduler, 
> > boost::threadpool::static_size, boost::threadpool::resize_controller, 
> > boost::threadpool::wait_for_all_tasks> >::run ()
> > #11 0x0805d4bc in boost::function0<void, std::allocator<boost::function_base> 
> > >::operator() ()
> > #12 0x080f94de in thread_proxy ()
> > #13 0x0817e8f4 in pthread_start_thread (arg=0x13966840) at manager.c:310
> > #14 0x081ae73a in clone ()
> >
> > Any ideas what can be wrong? (It works very fine if the code runs with
> > multiple threads on ONE CPU, but it starts failing if the threads are
> > distributed among 2 or more CPUs) 

What kernel do you use, Exact_pred_exact_constructions it seems ?
This one would also have some thread-safety issues, e.g. copying
points between threads...  Even the default constructed Point (or other
objects from this kernel) has a shared ref-counter...



I would be interested in knowing more details about your needs in this area.
(and from other people as well, if some subscribers have thread-safety 
requirements)

--
Sylvain Pion
INRIA Sophia-Antipolis
Geometrica Project-Team
CGAL, http://cgal.org/