CGAL users discussion list

[Graham Macpherson <>]

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;
}

#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;
}