CGAL users discussion list

[Sylvain Pion <>]

Laurent Rineau (GeometryFactory) a écrit :
> On Tuesday 08 December 2009 17:39:48 Ramin H wrote:
> > Hi everyone,
> >
> > I have GCC 4.4.1, CGAL 3.5, Ubuntu 9.10 running in a VMware virtual
> > machine, AMD Turion64-X2 processor and 1GB of RAM assigned to this
> > virtual machine.
> >
> > Compiling classes that contain CGAL code take an incredible amount of
> > time. For example, compiling
> > CGAL-3.5/examples/Mesh_3/mesh_polyhedral_domain.cpp  takes about 10
> > minutes to complete on my machine.
> >
> > This means, each time I change anything in this file, I have to wait
> > 10 minutes for the code in this file to get compiled. Now, if I have 2
> > or 3 classes with CGAL code, if I change anything in those files, I
> > have to wait even longer for the whole code to compile.
> >
> > Is this normal? Is there any trick to reduce compile time?
>
> With your compiler, that example needs more memory to compile. Probably the 
> compiler uses swap. You can try to remove -g from the compilation flags, to 
> reduce the memory need, or increase the memory of the virtual machine so that 
> the compilation does not use swap.

Here is the FAQ entry that I am compiling for this question.
I hope it helps...


#   How to reduce compilation time of programs using CGAL ?

CGAL is heavily using C++ templates, and this has an impact on compilation 
speed. Here are some hints that can help speed up compilation of programs 
using CGAL.

   * Remove compiler debugging options like -g if you can. Indeed, generating 
debug information can be very costly for template instantiations, both in 
terms of running time and memory usage by the compiler tool chain.
   * Remove compiler optimization options like -O2, when you do not need 
them, such as early in the development cycle of your programs.
   * Regroup translation units : if your program is composed of lots of small 
translation units to be compiled and linked, try to reduce their numbers by 
merging them. This traditional style for C programs is very slow for programs 
heavily using C++ templates. Regrouping them reduces the time spent by the 
compiler to parse the header files, and avoids redundant template 
instantiations.
   * Precompile header files : some compilers, such as GCC, provide a feature named precompiled headers. It can be mostly useful if you can regroup in a single header file most of the header files that you use, together with most template instantiations. Refer to your compiler documentation to use this. 


--
Sylvain Pion
INRIA Sophia-Antipolis
Geometrica Project-Team
CGAL, http://cgal.org/