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Re: [cgal-discuss] optimal_convex_partition_2 produces invalid decomposition


Chronological Thread 
  • From: Manoj Bist <>
  • To:
  • Subject: Re: [cgal-discuss] optimal_convex_partition_2 produces invalid decomposition
  • Date: Thu, 16 Sep 2021 17:11:14 -0700
  • Authentication-results: mail2-smtp-roc.national.inria.fr; spf=None ; spf=Pass ; spf=None
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I was able to merge the header files manually and it did fix the issue I was running into. Is it possible to comment on asymptotic complexity of the brute force fix?  Does it make the CGAL::approx_convex_partition_2 O(n^2) or not?

On Wed, Sep 15, 2021 at 1:23 PM Manoj Bist <> wrote:
The issue has been closed as duplicate. There is a temporary fix in a branch that is 5 years old.   Is it possible to merge it to the main branch?
I have tried manually merging it to the main branch but have been unsuccessful.  

On Tue, Oct 13, 2020 at 4:38 AM "Sebastien Loriot (GeometryFactory)" <> wrote:
I created the following issue to track the resolution of your bug:

https://github.com/CGAL/cgal/issues/5074

Best regards,

Sebastien.


On 10/1/20 8:37 PM, Manoj Bist ( via cgal-discuss
Mailing List) wrote:
>   have attached a testcase that illustrates the issue. Its a cpp file
> that you can compile to reproduce the issue.
>
> Please note that the input is valid. Approximate decomposition works
> correctly. Optimal decomposition fails in CGAL_partition_postcondition.
> /Please do not be confused by the name of CGAL ERROR: precondition
> violation. It is actually failing in the post condition, where in it
> verifies that the decomposition is correct./
>
> 1. I've verified that the input polygon is  a simple counter clockwise
> polygon. I have put the following two asserts to ensure this invariant.
>
>   assert(CGAL::is_simple_2(polygon.vertices_begin(),
> polygon.vertices_end(), Traits()));
> assert(CGAL::orientation_2(polygon.vertices_begin(),
> polygon.vertices_end(), Traits()) == CGAL::COUNTERCLOCKWISE);
>   assert(!hasDuplicatePoints(polygon));
>
> 2. To test the logical correctness for the input polygon, I have also
> done the following.
>
> I've identified a point that is outside the input polygon. A point that
> is outside the input polygon should be outside all the polygons in
> convex decomposition.
>
> Approximate decomposition passes this.
>
> 3. First I run the approximate
> decomposition CGAL::approx_convex_partition_2. It works as expected.
>
> 4. This post condition fails for optimal decomposition.
>
>        CGAL_partition_postcondition(
>               convex_partition_is_valid_2(polygon.begin(), polygon.end(),
>                                        res.output_so_far_begin(),
>                                        res.output_so_far_end(), traits)
>
>
>
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