Re: Vectors vs Arrays performance

We can come up with examples and counter-examples all day long.

Consider this:

int main()
{
    std::vector<int> v;
    v.reserve(1000);
    lib::vecarray<int, 1000> va;
    {
        timer t("vector: ");
        for (int i = 0; i != 1000000; ++i)
        {
            for (int j = 0; j != 1000; ++j)
                v.push_back(j);
            v.clear();
        }
    }
    {
        timer t("vecarray: ");
        for (int i = 0; i != 1000000; ++i)
        {
            for (int j = 0; j != 1000; ++j)
                va.push_back(j);
            va.clear();
        }
    }
}

Which outputs (several runs done, VC++ release build, secure STL disabled):

vector: 2.9741 seconds
vecarray: 2.6782 seconds

Which indicates (for this example) that a stack based container
(http://i42.co.uk/stuff/vecarray.htm) is 11% quicker than std::vector.

1) std::vector contains a pointer to its elements, a stack based container
(or an ordinary array on the stack) does not
2) you may benefit from the locality of your container and other local
variables (think CPU cache)

Have you seen the film "The Matrix"? "There is no spoon." "There is no
pointer.".

/Leigh