CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Graham Macpherson wrote:
> 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?
You were right, there seems to be a problem when using gcc 4.5.
I don't know right now what. I'll post here when I have more
information.

S.


> 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