Assertion Nef_3

[gdamiand]

Please use the following template to help us solving your issue.

Issue Details

The following code raise an assertion.

Source Code

surface_mesh_kernel.txt
data.zip

Environment

• Operating system (Windows/Mac/Linux, 32/64 bits): Ubuntu 24.04
• Compiler: g++ 13.2.0
• Release or debug mode: debug
• CGAL version: master branch

[afabri]

I turned this into PR #8646 without fix.

[afabri]

What assertion do you have? When I run the executable in the PR I get th output below without assertion.

andre@motherwell /cygdrive/c/GitHub/cgal/Nef_3/test/Nef_3
$ ./build/Debug/issue8644
0 0  0 0  0 -1  0 1
0 1  0 0  0 0  0 -3/2
0 0  0 -1  0 0  0 3
0 -1  0 0  0 0  0 3
0 0  0 1  0 0  0 3
0 1  0 0  0 0  0 3
0 0  0 -1  0 0  0 -3/2
0 0  0 0  0 1  0 1
[./data/lshape1_dim3.off]: empty kernel.
0 0  0 0  0 1  0 -1
0 -1  0 0  0 0  0 3/2
0 0  0 1  0 0  0 -3
0 1  0 0  0 0  0 -3
0 0  0 -1  0 0  0 -3
0 -1  0 0  0 0  0 -3
0 0  0 1  0 0  0 3/2
0 0  0 0  0 -1  0 -1
[./data/lshape1_dim3.off]: NON empty kernel.
0 -1  0 0  0 0  0 -3
0 0  0 0  0 -1  0 -1
0 0  0 -1  0 0  0 -3
0 0  0 0  0 1  0 -1
0 0  0 1  0 0  0 3/2
0 -1  0 0  0 0  0 3/2
0 0  0 -1  0 0  0 3/2
0 -1  0 0  0 0  0 -3
0 0  0 1  0 0  0 -3
0 1  0 0  0 0  0 -3
[./data/ushape1_dim3.off]: empty kernel.
0 1  0 0  0 0  0 3
0 0  0 0  0 1  0 1
0 0  0 1  0 0  0 3
0 0  0 0  0 -1  0 1
0 0  0 -1  0 0  0 -3/2
0 1  0 0  0 0  0 -3/2
0 0  0 1  0 0  0 -3/2
0 1  0 0  0 0  0 3
0 0  0 -1  0 0  0 3
0 -1  0 0  0 0  0 3
[./data/ushape1_dim3.off]: empty kernel.

[gdamiand]

Result using your branch PR #8646

./issue8644
0 0 0 0 0 -1 0 1
0 1 0 0 0 0 0 -3/2
0 0 0 -1 0 0 0 3
0 -1 0 0 0 0 0 3
0 0 0 1 0 0 0 3
0 1 0 0 0 0 0 3
0 0 0 -1 0 0 0 -3/2
0 0 0 0 0 1 0 1
[./data/lshape1_dim3.off]: empty kernel.
0 0 0 0 0 1 0 -1
0 -1 0 0 0 0 0 3/2
0 0 0 1 0 0 0 -3
0 1 0 0 0 0 0 -3
0 0 0 -1 0 0 0 -3
0 -1 0 0 0 0 0 -3
0 0 0 1 0 0 0 3/2
0 0 0 0 0 -1 0 -1
[./data/lshape1_dim3.off]: NON empty kernel.
0 -1 0 0 0 0 0 -3
0 0 0 0 0 -1 0 -1
0 0 0 -1 0 0 0 -3
0 0 0 0 0 1 0 -1
0 0 0 1 0 0 0 3/2
0 -1 0 0 0 0 0 3/2
0 0 0 -1 0 0 0 3/2
0 -1 0 0 0 0 0 -3
0 0 0 1 0 0 0 -3
0 1 0 0 0 0 0 -3
[./data/ushape1_dim3.off]: empty kernel.
0 1 0 0 0 0 0 3
0 0 0 0 0 1 0 1
0 0 0 1 0 0 0 3
terminate called after throwing an instance of 'CGAL::Assertion_exception'
what(): CGAL ERROR: assertion violation!
Expr: normalized(cet->circle()) == normalized(ce->circle().opposite())
File: /home/gdamiand/sources/cgal/Nef_3/include/CGAL/Nef_3/SNC_external_structure.h
Line: 620
Abandon (core dumped)

[afabri]

Did you get that in the code I have put in the pull request? What you have put in surface_mesh_kernel.txt does not even compile, as you probably extracted it from some application.

[afabri]

Just saw "./issue8644" , so it is in my branch. I do not have the assertion. What is your test platform? Let me flag it ready for testing so that we see it in the testsuite.

[afabri]

Hello @gdamiand
So it fails on some platforms in testsuite 6.1-Ic-38

[gspr]

I think I'm seeing this assertion failure with a simpler example, too. Consider:

#include <CGAL/Extended_cartesian.h>
#include <CGAL/Gmpq.h>
#include <CGAL/Nef_polyhedron_3.h>

using Kernel = CGAL::Extended_cartesian<CGAL::Gmpq>;
using Nef = CGAL::Nef_polyhedron_3<Kernel>;

int main(int argc, char ** argv)
{
  Nef hspace_1(Nef::Plane_3(1.0, 0.0, 0.0, 0.0), Nef::INCLUDED);
  Nef hspace_2(Nef::Plane_3(1.0, 0.0, 0.0, 1.0), Nef::INCLUDED);
  Nef hspace_3(Nef::Plane_3(0.0, 0.0, 1.0, 1.0), Nef::INCLUDED);

  Nef intersection_1 = hspace_1*hspace_2; // Line 14. Works fine.
  Nef intersection_2 = hspace_2*hspace_3; // Line 15. Assertion failure.
  
  return 0;
}

The computation on line 14 works fine, while the one on line 15 fails at the assertion in question. Here's the backtrace (captured with version 5.5.1, so it might differ from one captured at git HEAD):

#6  0x00007ffff7ca90d8 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc++.so.6
#7  0x000055555555d592 in CGAL::assertion_fail (expr=0x55555562b7a0 "normalized(cet->circle()) == normalized(ce->circle().opposite())", 
    file=0x55555562b710 "/usr/include/CGAL/Nef_3/SNC_external_structure.h", line=691, msg=0x55555562a09c "")
    at /usr/include/CGAL/assertions_impl.h:173
#8  0x000055555556d158 in CGAL::SNC_external_structure_base<CGAL::SNC_items, CGAL::SNC_structure<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool> >::link_shalfedges_to_facet_cycles (this=0x7fffffffdb90) at /usr/include/CGAL/Nef_3/SNC_external_structure.h:691
#9  0x0000555555566058 in CGAL::SNC_external_structure_base<CGAL::SNC_items, CGAL::SNC_structure<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool> >::build_external_structure (this=0x7fffffffdb90) at /usr/include/CGAL/Nef_3/SNC_external_structure.h:1014
#10 0x0000555555571fb8 in CGAL::SNC_external_structure_base<CGAL::SNC_items, CGAL::SNC_structure<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool> >::build_after_binary_operation<CGAL::ID_support_handler<CGAL::SNC_items, CGAL::SNC_decorator<CGAL::SNC_structure<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool> > > > (this=0x7fffffffdb90) at /usr/include/CGAL/Nef_3/SNC_external_structure.h:1049
#11 0x000055555556758c in CGAL::Binary_operation<CGAL::SNC_structure<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool> >::operator()<CGAL::Nef_polyhedron_3<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool>::AND> (this=0x7fffffffdd70, pl0=0x55555573d6d0, snc1=..., 
    pl1=0x5555556c5e90, snc2=..., pl2=0x5555556f51a0, BOP=...) at /usr/include/CGAL/Nef_3/Binary_operation.h:525
#12 0x0000555555563119 in CGAL::Nef_polyhedron_3<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool>::intersection (
    this=0x7fffffffde40, N1=...) at /usr/include/CGAL/Nef_polyhedron_3.h:1416
#13 0x0000555555561c47 in CGAL::Nef_polyhedron_3<CGAL::Extended_cartesian<CGAL::Gmpq>, CGAL::SNC_items, bool>::operator* (this=0x7fffffffde40, 
    N1=...) at /usr/include/CGAL/Nef_polyhedron_3.h:1488
#14 0x000055555555ae83 in main (argc=1, argv=0x7fffffffe048) at test-2.cpp:15