CGAL users discussion list

[Manuel Caroli <>]

Hi Graham,

the move function does not seem to be documented, is it?
Anyway, you are using the Triangulation hierarchy. Currently the move 
function is not implemented in Triangulation_hierarchy_2 but does only 
work for Delaunay_triangulation_2.
So you either use Delaunay_triangulation_2 or you just call insert and 
remove depending on what makes more sense for your application.

best

Manuel


Graham Macpherson wrote:
> Hi Manuel,
>
> > Could you send a minimal example that produces the error?
>
> Attached and at the bottom of this email is an example.  The objective is at 
> each step to move or remove some points from the triangulation, and then add 
> some more.
>
> I get an seg fault within 2-3 steps (no DEBUG) or the "is_valid" assertion 
> fails at the first step (DEBUG) with both exact and inexact kernels.
>
> If I comment out "move", or replace it with the commented out "insert and 
> remove", then the problem stops happening.  If I just "move" the points (no 
> removal or insertion) then it fails the assertion in DEBUG, but *doesn't* seg 
> fault with no DEBUG.
>
> Am I using the "move" function inappropriately or incorrectly?
>
> Thanks very much for your help,
>
> Graham
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
> #include <CGAL/Exact_predicates_exact_constructions_kernel.h>
> #include <CGAL/Delaunay_triangulation_2.h>
> #include <CGAL/Triangulation_hierarchy_2.h>
> #include <CGAL/point_generators_2.h>
> #include <CGAL/Random.h>
> #include <CGAL/algorithm.h>
>
> typedef CGAL::Exact_predicates_exact_constructions_kernel K;
> // typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
>
> typedef CGAL::Triangulation_vertex_base_2<K>             Vbb;
> typedef CGAL::Triangulation_hierarchy_vertex_base_2<Vbb> Vb;
> typedef CGAL::Triangulation_face_base_2<K>               Fb;
> typedef CGAL::Triangulation_data_structure_2<Vb,Fb>      Tds;
> typedef CGAL::Delaunay_triangulation_2<K,Tds>            Dt;
> typedef CGAL::Triangulation_hierarchy_2<Dt>              Triangulation;
> typedef Triangulation::Point                             Point;
> typedef CGAL::Creator_uniform_2<double,Point>            Creator;
>
> int main( )
> {
>     Triangulation t;
>
>     CGAL::Random r;
>
>     CGAL::Random_points_in_square_2<Point,Creator> g(1.0);
>
>     CGAL::copy_n( g, 10000, std::back_inserter(t));
>
>     for (int s = 0; s < 100; s++)
>     {
>         std::cout << "\nstep " << s << std::endl;
>
>         for
>         (
>             Triangulation::Finite_vertices_iterator vit =
>                 t.finite_vertices_begin();
>             vit != t.finite_vertices_end();
>             ++vit
>         )
>         {
>             if (r.get_double() > 0.9)
>             {
>                 t.remove(vit);
>             }
>             else
>             {
>                 t.move
>                 (
>                     vit,
>                     vit->point()
>                   + K::Vector_2(r.get_double(0, 0.1), r.get_double(0, 0.1))
>                 );
>
>                 // t.insert
>                 // (
>                 //     vit->point()
>                 //   + K::Vector_2(r.get_double(0, 0.1), r.get_double(0, 0.1))
>                 // );
>
>                 // t.remove(vit);
>             }
>         }
>
>         assert(t.is_valid());
>
>         std::cout << "Insert more vertices" << std::endl;
>
>         for (int i = 0; i < 1000; i++)
>         {
>             t.insert
>             (
>                 Point(r.get_double(0, 1.0) - 0.5, r.get_double(0, 1.0) - 0.5)
>             );
>         }
>
>         std::cout << t.number_of_vertices() << std::endl;
>     }
>
>     return 0;
> }