When the Quake III Arena source code was released to the world it contained a previously unknown algorithm called the Fast Inverse Square Root. This is the story of this strange algorithm and how it works as told by retired Microsoft software engineer Dave Plummer. For more info on the FISR: A great video with better math explanations: https://www.youtube.com/watch?v=p8u_k2LIZyo A surprisingly complete and detailed Wikipedia article: https://en.wikipedia.org/wiki/Fast_inverse_square_root Amazon Affiliate links for products mentioned in the video: Zen of Code Optimization - https://amzn.to/2VO7ltx Zen of Graphics Programming - https://amzn.to/3AxTAh9 Zen of Assembly [Out of Print] - https://amzn.to/2VD7Arn Errata: If you find mistakes or important omissions, please let me know and I'll update this! Credits: Thanks to my great-grandfather Plummer for standing in as Monte, and to viewer Brandon Pinske for the video topic suggestion! 00:00 Intro 00:35 Welcome 01:20 Recap 03:12 Racing Talk 05:30 Gates and Allen 08:20 Fixed Point 09:30 Floating Point 11:46 Historical Info 13:00 One Weird Trick 14:35 Constant Confusion 16:53 Race Prep 18:05 4 v 4 19:58 Conclusion