CGAL users discussion list

[Ben Haller <>]

  Hi all.  I've been using the Delaunay_d CGAL code for a while to do 3D 
triangulations, which has worked very well.  I recently tried to step it up 
to 4D and 5D triangulations, and things are not going so well.  CGAL is 
causing a segfault because it is blowing through the maximum stack size 
(which is 8 MB on OS X) around the 790th 5D point added to the triangulation. 
 I tried giving it 16 MB of stack to give it more headroom, but then it just 
blows through it a little later (around the 1250th point added).  It also 
gets extremely slow at adding points compared to the 3D case; adding 16384 
points in 3D takes just a couple of minutes total on my machine, but adding 
4D or 5D points gets to taking as long as a minute per point added (before it 
causes the segfault).  I was hoping to add as many as 100,000 points to my 5D 
triangulation, but clearly this is not going to work.

  Is this known / expected?  Maybe doing triangulations in more than three 
dimensions is inherently extremely difficult; but it kind of feels like the 
CGAL code might be switching algorithms "under the hood" for >3 dimensions, 
and maybe the algorithm it switches to is not so good.  Or have others been 
successful doing this kind of thing, and there is something about the way I'm 
using CGAL that is causing problems?

Ben Haller
McGill University