Fast inverse square root

Have you ever heard of a fast inverse square root? No? Let me explain.

Imagine you have a toy car and you want to find out how fast it can go around a curve without tipping over. In order to do that, you need to know how much force is acting on the car. One important force is called gravity and it affects how much the car leans on the curve. The formula for this force involves a term called the "inverse square root" which is a fancy way of saying "divide one by the square root of something".

Now, doing math operations like taking a square root can be slow and take up a lot of time and resources on a computer. But mathematicians and computer scientists have come up with a clever trick to make finding the inverse square root really fast. It involves using a special number called a floating-point representation, which allows us to represent numbers with a lot of precision and without using too much memory.

The fast inverse square root technique was first popularized in the early 2000s by game programmers who needed to do many calculations in real-time while keeping good performance. It became especially famous for its use in the game Quake, where its speed was necessary for smooth gameplay.

So, in short, fast inverse square root is a clever trick that uses a special representation of numbers, making it faster to find the force of gravity on objects, such as toy cars or 3D game characters, or anything else that needs fast calculations.