Why is std::sin() and std::cos() slower than sin() and cos()?

Question

Test code:

#include 
#include 

const int N = 4096;
const float PI = 3.1415926535897932384626;

float cosine[N][N];
float sine[N][         


        

Answer 1

I guess the difference is that there are overloads for std::sin() for float and for double, while sin() only takes double. Inside std::sin() for floats, there may be a conversion to double, then a call to std::sin() for doubles, and then a conversion of the result back to float, making it slower.