CGAL users discussion list

[Graham Macpherson <>]

Hi Sebastien,

Thanks for the reply.

I've checked and I do see the linear memory increase with openSUSE and not 
with
Ubuntu; the logs I attached to my email are valid.

Is it worth investigating if gcc 4.4 vs 4.5 makes a difference?

Regards,

Graham



On Monday 17 January 2011 08:40:52 Sebastien Loriot (GeometryFactory) wrote:
> There is no memory leak in your code.
>
> Behind the Exact_predicates_exact_constructions_kernel, there are
> *a multi-precision number type (for example Gmpq if GMP is available)
> *filtering mechanism on constructed objects (such as points)
>
> In your for loop, you are iteratively summing to your points a vector.
> Both implementation details are responsible for the memory increase:
>
> *The precision needed by the number type to exactly do the sums
> requires more precision, thus more space. Running you code with
> CGAL::Simple_cartesian<CGAL::Gmpq>, you will observe an increase in
> memory usage, but not at each iteration (only when precision of numbers
> is increased).
>
> *the filtering mechanism maintain a DAG of the cascaded constructions.
> Each sum create a note in the DAG. This is the real cause of the memory
> usage increase in your case.
>
>
> However, I am surprised that you do not observe the memory consumption
> increase on Ubuntu.
> Can you please check again to confirm whether there is a problem?
>
> S.
>
> Graham Macpherson wrote:
> > Hello all,
> >
> > I've found a strange memory problem that I've reproduced in the attached 
> > code.
> >
> > I'm taking the vertices of a Delaunay tessellation, calculating a 
> > displacement
> > for them, clearing the tessellation, then reinserting the displaced 
> > vertices.
> > When I run this, the memory use by the process increases linearly with 
> > each
> > iteration, which is wrong, it should be essentially constant, however:
> >
> >  + The problem doesn't occur with option A in the attached, only with 
> > option B,
> >    i.e. when adding a Vector_3 to the point;
> >
> >  + The problem doesn't occur using
> >    Exact_predicates_inexact_constructions_kernel, only with
> >    Exact_predicates_exact_constructions_kernel;
> >
> >  + It doesn't appear on all operating systems - it appears on openSUSE 
> > 11.3, but
> >    not on Ubuntu 10.04.
> >
> > Also attached are two log files showing the contrasting behaviour on the 
> > two
> > operating systems with the code the same.
> >
> > I've tried on openSUSE 11.3 with gcc 4.5.0 (system compiler) and gcc 
> > 4.5.2,
> > boost versions 1.40.0, 1.42.0 (system) and 1.45.0, and with CGAL 3.5.1 
> > and CGAL
> > 3.7, and they all essentially do the same thing.
> >
> > On Ubuntu I'm using CGAL 3.7, gcc 4.4.3 (system compiler) and boost 1.40.0
> > (system).
> >
> > Note, the memInfo class is one that's part of other libraries I'm using, 
> > so it
> > won't compile for you, it's only there to show how the output was 
> > generated.
> >
> > Assuming that the addition operation in option B is legitimate, then this 
> > looks
> > like a bug in a library.  Any suggestions for how to get to the bottom of 
> > it?
> >
> > Best regards,
> >
> > Graham
> >
> > --
> > Graham Macpherson
> >
> > OpenCFD Ltd.
> > www.openfoam.com
> >
> > 
> > +44 (0)118 9471030
> >
> > 9 Albert Road
> > Caversham
> > Reading RG4 7AN
> >
> >
>
>
>
>