C++0x issue: Constant time insertion into std::set

Question

According to this page, I can achieve constant time insertion if I use

iterator std::set::insert ( iterator position, const value_type& x );

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Answer 1

Is it cheating to run a test instead of reading through library specifications?

For g++-4.4 -O2 for the integers 0 <= i < 5000000 my running times for standard insertion are

real    0m14.952s
user    0m14.665s
sys 0m0.268s

and my running times for insertion using end() as hint are

real    0m4.373s
user    0m4.148s
sys 0m0.224s

Insertion at end() - 1 is just as fast as far as I can tell, but it is more cumbersome to use because end() - 1 is an illegal operation (you have to use operator--()) and it crashes if the set happens to be empty.

#include 

typedef std::set Set;

void insert_standard(Set& xs, int x)
{
    xs.insert(x);
}

void insert_hint_end(Set& xs, int x)
{
    xs.insert(xs.end(), x);
}

int main()
{
    const int cnt = 5000000;
    Set xs;
    for (int i = 0; i < cnt; i++) {
        // insert_hint_end(xs, i);
        insert_standard(xs, i);
    }
}