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

Following in the footsteps of @antonakos, I'm expanding on the "cheating" solution and running an empirical test. I'm using GCC 4.5 with optimization (-02) and considering both the case when C++0x support is not enabled and when it is with -std=c++0x. Results on 40,000,000 insertions are as follows (showing system time as the other values in this case are not special):

• Without C++0x support
  • No hint: 26.6 seconds
  • Hint at end(): 5.71 seconds
  • Hint at --end(): 5.84 seconds
• With C++0x support enabled
  • No hint: 29.2 seconds
  • Hint at end(): 5.34 seconds
  • Hint at --end(): 5.54 seconds

Conclusion: GCC (with or without C++0x enabled) inserts efficiently when end() is provided as the insertion hint.

The code I used is based on @antonakos's:

#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);
}

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

int main() {
    const int cnt = 40000000;
    Set xs;
    xs.insert(0);
    for (int i = 1; i < cnt; i++) {
        //insert_standard(xs, i);
        //insert_hint_one_before_end(xs, i);
        insert_hint_end(xs, i);
    }

    return 0;
}