CGAL users discussion list

[Marc Glisse <>]

On Sun, 24 Oct 2010, Bernhard Kornberger wrote:

> 1) I need an exact constructions kernel for the computation
> of intersections and orientations. According to an older
> posting, Gmpq is not thread-safe. Is this still true?

Yes, in the sense that a Gmpq shouldn't be accessed (even read-only) from 
different threads. However you can use different Gmpq objects in different 
threads. So if you first compute a structure and then use it read-only in 
several threads, you can make one copy of the whole structure per thread 
and use those instead.


> Is a #define necessary to specify thread-safety?

There is no such thing available for Gmpq. But see this link:

http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Preliminaries/Chapter_main.html#Section_2.6


CGAL::Cartesian<mpq_class> might work for you.


> 2) I assume that a Gmpq value, written to a file using
> outFile<<q and read again is the same? Just to be sure
> that the exactness is not lost in this step.

I think so.

--
Marc Glisse