CGAL users discussion list

Quoting "Ben Supnik" 
<>:

> Hi Efi,
>
> Foo - I can't reproduce the problem.  My old code was based on  
> building the map out of a series of boolean operations...because of  
> the poor performance of this structure, I rewrote the code a few  
> days ago to do a single massive insert_curves, and the map as it is  
> built now won't fail with the addition sweep visitor.

I guess this is good.
> I think the most likely problem is that I violated some kind of  
> precondition requirement for the boolean operations code, resulting  
> in an illegal shortcut in the boolean ops that produced a bogus map.  
> :-( The map would pass is_valid but perhaps that test isn't  
> conclusive?

Having a small program that reproduces a bug is the only way we are  
prepared to deal with bugs now days, so if it re-occurs, I'll be happy  
to debug a small test case.

The is_valid() function might be non conclusive. I would call it a  
bug, perhaps not a critical one. If you are able to produce an invalid  
arr. that is not caught by the is_valid() function, let us know.

> cheers
> Ben
>
>
> Efraim Fogel wrote:
> > Ben Supnik wrote:
> > > Hi Y'all,
> > >
> > > I have an arrangement (built out of join and difference operations  
> > > on polygons).  I am using an exact pred/exact constructions kernel  
> > > and half -frounding-math on.  I am in debug mode, so I have all  
> > > warnings, etc.
> > >
> > > After building my arrangement, I do an insert-curves on an  
> > > axis-aligned bounding box that sometimes overlaps the horizontal  
> > > and vertical edges of my map.
> > >
> > > If I insert the four sides using insert_curve, all is good.
> > > If I insert all four using insert_curves, I get an assertion  
> > > failure when trying to split a face.
> > >
> > > Now...looking at the code it seems clear that I should be using  
> > > insert_curve anyway; doing a full copy of the arrangement to put  
> > > only four curves in will be dominated by the copy cost.
> > There are cases where applying incremental inserts is more  
> > efficient than an applying an aggregate insert, especially when the  
> > number if input curves is small, but which copy of arrangement do  
> > you refer to?
> > > But...is there any case where the sweep-line-based insert_curves  
> > > should blow up?  I am concerned that either my map is secretly  
> > > invalid (it passes validation checks) or I have compiler settings  
> > > such that my numerics are not stable.
> > We are not aware of any bug of that sort. Try to come up with a  
> > test case that exposes the problem, and that we can reproduce, and  
> > we'll look at it.
> > > cheers
> > > ben
>
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