Which is the fastest way to get the absolute value of a number

Question

Which is the fastest way to implement an operation that returns the absolute value of a number?

x=root(x²)

or

if !isPositiv         


        

Answer 1

If you are simply comparing the absolute values of two numbers (e.g. you don't need the absolute value of either after the comparison) then just square both values to make both positive (remove the sign of each value), the larger square will be greater than the smaller square.