February 1st: Exploring the QUAKE III Fast Inverse Square Root by Daniel Harrington

For more information on the seminar, see: pgadey.ca/semi....
Abstract: QUAKE III’s fast inverse square root algorithm. The mysterious and ingenious function that made waves on the internet in 2002. Why did this strange piece of game engine code, with comments containing profanity and calling itself evil, make a common operation 4x faster? We will look into how this famous approximation worked, outsmarting the standards it was written in before applying clever bit manipulation and some calculus. Then we will discuss how it can be improved, and where it is today. Basic knowledge of programming is recommended.
#mtbos #quake3 #seminar #magicnumber #floatingpoint

[@Firnael]

Really inspiring work ! I think there is a typo at 30:29, f(y_n) should be "1/y^2 - x", instead of "1/y^2 + x" (even though it does not affect the derivative, it should mess with your signs, but you fixed it at 30:36)
Very cool anyway !

[@danielharringtonportfolio1872]

Thank you! I've never had my work called inspiring before I am flattered. I double checked the math and it seems you are right, I think it is a remnant from some factoring I decided I didn't need to do but good catch!