CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Could you give the 4.7 release a try?
The 2D minkowski sum package have been partly rework?

Thanks,

Sebastien.


On 10/09/2015 07:36 AM, Panaghis Mavrokefalos wrote:
> Hello,
>
> I have been using the minkowski_sum_2() function from the 2D Minkowski Sums
> package to compute the sums of some non-convex, but simple polygons. In
> some of
> my test cases, I noticed CGAL assertion failures (pre- and post-condition
> failures) at runtime, which I traced to calls of that function. I am
> aware that
> these sort of errors occur when using a kernel with inexact
> consrtuctions, but
> I made sure I was using the Exact_predicates_exact_constructions_kernel. At
> first, I tried replacing the default (convolution) strategy with a
> decomposition strategy (I chose Greene_convex_decomposition_2), but then the
> errors occurred in another test case.
>
> A test file is attached, reproducing the cases which triggerred the
> errors. The
> CMakeLists.txt file is generated using `cgal_create_CMakeLists -s main`.
> I am
> building with g++ version 4.8.4 and using CGAL version 4.5.1, configured
> with
> CMAKE_CXX_FLAGS=-frounding-math -std=c++11.
>
> There are four different test cases, corresponding to the first command line
> argument of the executable equal to 0 through 3. The simplicity of the input
> polygons to the minkowski_sum_2() function is explicitly tested before the
> call. For each test case, the output of the run of the executable is shown:
>
> ./main 0
>
> p is simple
> q is simple
> Computing the Minkowski sum of p and q using the default strategy
> terminate called after throwing an instance of
> 'CGAL::Precondition_exception'
>    what():  CGAL ERROR: precondition violation!
> Expr: nodeP != NULL && nodeP->is_valid()
> File: /usr/local/include/CGAL/Multiset.h
> Line: 339
> Aborted
>
> ./main 1
>
> p is simple
> q is simple
> Computing the Minkowski sum of p and q using the default strategy
> terminate called after throwing an instance of 'CGAL::Assertion_exception'
>    what():  CGAL ERROR: assertion violation!
> Expr: (!is_valid(i)) || (!is_valid(s)) || (!(i>s))
> File: /usr/local/include/CGAL/Interval_nt.h
> Line: 139
> Explanation:  Variable used before being initialized (or CGAL bug)
> Aborted
>
> ./main 2
>
> p is simple
> q is simple
> Computing the Minkowski sum of p and q using the default strategy
> terminate called after throwing an instance of
> 'CGAL::Precondition_exception'
>    what():  CGAL ERROR: precondition violation!
> Expr: nodeP != NULL && nodeP->is_valid()
> File: /usr/local/include/CGAL/Multiset.h
> Line: 339
> Aborted
>
> ./main 3
>
> p is simple
> q is simple
> Computing the Minkowski sum of p and q using the Greene decomposition
> strategy
> terminate called after throwing an instance of
> 'CGAL::Postcondition_exception'
>    what():  CGAL ERROR: postcondition violation!
> Expr: convex_partition_is_valid_2(polygon.vertices_begin(),
> polygon.vertices_end(), res.output_so_far_begin(),
> res.output_so_far_end(), traits)
> File: /usr/local/include/CGAL/Partition_2/partition_greene_approx_convex_2.h
> Line: 834
> Aborted
>
> Since, as mentioned before, I am using an exact constructions kernel, and a
> variety of different errors are produced, I am at a loss as to what is
> wrong.
> Any help would be greatly appreciated.