CGAL users discussion list

[Clément Jamin <>]

Hi Julian,

On Tue, Oct 4, 2016 at 12:01 AM, Julian Panetta
<>
 wrote:
> Dear Clément,
>
> Thanks for the explanation! I'd searched the manual before posting and
> couldn't find anything about this. If this isn't already documented
> somewhere, maybe it's worth adding to the "Parallel Algorithms" section?

You are right. Let me add this to my TODO-list.
Thanks.

> The extra points indeed cause no harm in my application, but worried me that
> something had broken.
>
> -Julian
>
> On Mon, Oct 3, 2016 at 10:47 AM, Clément Jamin 
> <>
> wrote:
>>
>> Hi Julian,
>>
>> On Sat, Oct 1, 2016 at 11:07 PM, Julian Panetta 
>> <>
>> wrote:
>>>
>>>
>>> Running make_mesh_3 in parallel gives a similar output to the sequential
>>> version, but it's consistently surrounded by 20 disconnected vertices all
>>> well outside the domain's bounding sphere (marked with "plus" signs in the
>>> attached image).
>>>
>>> Of course I can remove these, but it's disconcerting. Any ideas what's
>>> happening?
>>
>>
>> Yes, this is normal. Those points are added to get a better speed-up when
>> parallelism is activated.
>> Basically, the Delaunay triangulation used by the mesher has an infinite
>> vertex (see here http://doc.cgal.org/latest/Triangulation_3/index.html). A
>> lot of cells are adjacent to this vertex, so there is contention on it when
>> several threads work in parallel on the triangulation. Adding those "far
>> points" reduces contention.
>> We could remove them after the meshing process, but it is costly. They
>> usually do not harm since they are not adjacent to any cell of the mesh.
>>
>> Clément.
>>>
>>>
>>> For example, I see this in the implicit sphere example after pasting:
>>>
>>> #define CGAL_LINKED_WITH_TBB
>>> #define CGAL_CONCURRENT_MESH_3
>>>
>>> before the CGAL includes (and changing CGAL::Default to K to build on
>>> CGAL 4.8.1).
>>>
>>> Thanks,
>>> Julian
>>>
>>
>