Re: Vector vs. Array
Peter Vermeer wrote:
Hi,
I have implemented Manhattan Distance computation one time with
arrays and and one time with vectors:
float manDist(vector<float>& v1, vector<float>& v2)
{
float sum = 0;
for (int i = 0; i < 100; i++)
{
sum += fabs(v1[i]-v2[i]);
}
return sum;
}
float manDist(float v1[], float v2[])
{
float sum = 0;
for (int i = 0; i < 100; i++)
{
sum += fabs(v1[i]-v2[i]);
}
return sum;
}
Curiously, the array version is much faster (factor 100). So
probably, there is something wrong with my code. I have tested also
iterators instead of [] as well as at() instead of [] for vectors.
Furthermore, I defined _SECURE_SCL 0.
Can someone enlighten me?
Are you running in debug mode? :-)
Testing them with a main function like:
int main()
{
vector<float> v1(100), v2(100);
return int(manDist(v1, v2) + manDist(&v1[0], &v2[0]));
}
shows that the two functions produce identical assembly code. MSVC10
Express, Release mode.
Bo Persson
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