# Quake III & the reciprocal square root

A marveleous algorithm for a fast computation of the reciprocal square root

In the C source code of the famous game *“Quake III — Arena” *you can find an incredibly efficient piece of code that seems totally insane and incomprehensible! It is the code for computing the reciprocal of the square root of a 32-bit floating point number x. It is usually also known as Fast Inverse Square Root, but I…