Re: iterator and index

It occured to me that which of iterator or index is faster in loops.
Then I tried the code below:
//////////////////////////////
#include<vector>
#include<iostream>
using namespace std;

int main()
{
    vector<int> vi;
    for(int i=0;i!=100000;++i)
        vi.push_back(i);
    for(size_t i=0;i!=vi.size();++i) //for(vector<int>::iterator
iter=vi.begin();iter!=vi.end();++i)
            cout<<vi[i]<<endl; // cout<<*iter<<endl;
}
//////////////////////////////
I thought this design was not good.It depent on many factors.
The result is not so exact. It showed that the iterator is a little
faster. But I found that "The execute file that I re-built each time
didn't take equal time,and the disparity was obviously."

Could someone tell me the matter with iterator and index?

And whether is "vi.end()" called when each loop happens?
And if I change the code of iterator to:

              vector<int>::iterator x=vi.end();
              for(vector<int>::iterator iter=vi.begin(); iter!=x;
++i)
 will it take less time?

Thank you !