Performance of vector::size() : is it as fast as reading a variable?

Question

I have do an extensive calculation on a big vector of integers. The vector size is not changed during the calculation. The size of the vector is frequently accessed by the c

Answer 1

Always get a profile of your application before looking at this sort of micro optimization. Remember that even if it performs a subtraction, the compiler could still easily optimize it in many ways that would negate any performance loss.