CGAL users discussion list

[Ashwin Nanjappa <>]

Rafael Roberto wrote:
> But now, I have a doubt: what is the real difference between 
> Exact_predicates_exact_constructions to 
> Exact_predicates_inexact_constructions?

Predicates are geometric tests where only the polarity of the result is of 
interest (like pass/fail). Constructions are calculations that result in new 
geometric entities. Now, all geometric algorithms in theory deal with 
numbers of infinite precision. However, when we calculate on the computer we 
are restricted to finite precision. Calculations of "exact" arithmetic can 
be attempted, but it will slow down the program.

So, these 2 kernels offer tradeoffs between speed and precision. As their 
titles indicate, predicates are exact in both, but constructions aren't in 
E_P_I_C. But, E_P_I_C is faster than E_P_E_C.

See for more details:
<http://www.cgal.org/Manual/3.3.1/doc_html/cgal_manual/Kernel_23_ref/Class_Exact_predicates_inexact_constructions_kernel.html>
<http://www.cgal.org/Manual/3.3.1/doc_html/cgal_manual/Kernel_23_ref/Class_Exact_predicates_exact_constructions_kernel.html>

~ash