REVEALED: Quake III's SECRET Algorithm!

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. Thanks to viewer Brandon Pinske for the video topic suggestion! For more info on the FISR: A great video with better math explanations: https://youtu.be/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 Chapter Markers: 00:00 The Story 02:10 Welcome 03:25 Vectors 04:30 Normalization 05:48 Pythagoras Redux 07:50 Behold Code 09:10 Roots and Floats 10:21 Newton, Approximately 11:14 Rate of Change 13:02 C++ Code 14:15 Gates and Allen 15:04 Outtakes and Rarities Errata: Please let me know in the comments of any important errors or omissions, and I will update things here. Currently, the only major update is at the end - I leave you with the impression that IEEE-754 might have been based on MBF, but I don't think that's the case. I will expand on this in Part 2, but recommend these two links for the curious: • "The IEEE Standard 754: One for the History Books," https://www.computer.org/csdl/magazine/co/2019/12/08909942/1f8KFWxbTCU • "An Interview with the Old Man of Floating-Point," http://people.eecs.berkeley.edu/~wkahan/ieee754status/754story.html