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[Narusaki <>]

Hi, 

I'm using the Nef_polyhedron_2 to execute intersection of some polygons
(constructed from several half-lines and may be unbounded). 

The question is: When I did it with only a single thread, it is OK; but when
I've tried with multiple threads using OpenMP, there is an assertion in the
locate() method of a Voronoi_diagram_2 object being triggered. 

At last I locate the problem at some part about the intersection of
Nef_polyhedrons. I guess there is sth wrong in the operator *= (i.e. the
intersection operation) of the Nef_polyhedron_2 because when I comment the
following code:

int idx = omp_get_thread_num();
vorCellNef *= boundaryNefs[idx];

No assertion is triggered anymore. I don't know how this piece of code can
affect the locate() method. On the other side, both of the two
Nef_polyhedron_2 objects (vorCellNef and boundaryNefs[idx]) on the two sides
of *= are local variables for each thread, so I guess it should be OK even
if the Nef_polyhedron_2 is not thread-safe.

Does anyone know what may go wrong here? Thanks very much.



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