Re: Amazing Performance Difference between vec[] and iterators

[thoth39]

Ulrich Lauther wrote:
> Paulo Matos <pocmatos@gmail.com> wrote:
> : Hi all,
>
> : I've wanted to know if there was any performance difference between
> : using:
> : for(vector<int>::const_iterator it = v.begin(); it != v.end(); ++it)
>
> : and
>
> : for(unsigned int k = 0; k < v.size(); ++k)
>
> Try
>
> unsigned int size = v.size();
> for (unsigned int k = 0; k < size; ++k)
>
> in your version size() is evaluated size times

Likewise, instead of

for(vector<int>::const_iterator it = v.begin(); it != v.end(); ++it)

try

for(vector<int>::const_iterator it = v.begin(), end = v.end(); it !=
end; ++it)

to avoid calling v.end() every time.