CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

Le vendredi 03 août 2012 14:03:24 

 a écrit :
> Hi,
> thank you for your reply!
> 
> > So, I'm wondering whether:
> > 1) The allocation error is connected with a size-limit for Eigen
> 
> matrixes.
> 
> > std::bad_alloc is the exception that is thrown when a 'new' operator
> > cannot
> > allocate the requested memory. It means that, with the number you gave
> 
> us,
> 
> > the
> > Eigen matrix is probably too big to fit in your memory. If you compile
> > your
> > program in 32 bits, it can also mean that you may have enough memory,
> 
> but
> 
> > the
> > requested memory does not fit in the memory space that a process can use
> > in
> > 32 bits (that is less than 4Go).
> 
> A memory problem was also my guess. Anyway I was surprised as  I run  the
> huge case (Number of verticesDT 2971971 Number of cellsC3T3 18586265) on a
> machine with 20Go of memory.
> Do you have any suggestions?

Do you compile your program using a 64 bits compiler? What is the expected 
size of matrix for 2971971 vertices ?

> > 2) It is possible to accelerate intersection procedure.
> > What is the set of lines that you use?
> 
>  I build a vector of directions corresponding to the direction of the
> segments connecting the center of a sphere with points uniformly
> distributed on its surface. Then I build a set of lines with these
> directions and crossing each vertex using an exact kernel to build
> intersections (the Exact_predicates_inexact_constructions_kernel used to
> generate the mesh gave me inexact results for intersections).

If the lines rarely intersect the triangles, you should try to detect if 
there 
is an intersection, using CGAL::do_intersect or Kernel::Do_intersect_3 with 
the Exact_predicates_inexact_constructions_kernel, and only use the "exact-
exact" kernel where the intersection exists. That should speed up your 
intersection computations.

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/