is fast inverse square root relevant in 2021

Question

fast inverse square root algo from quake game engine

is the algo relevant in 2021

Answer 1

No. I can't think of a good reason to add a library or add code for the fast inverse square root algorithm in any modern software. It might be useful to understand for educational purposes but I think you're looking for more practical use.

All computing devices that show 3D graphics are so much faster now than desktops back in 1999 that the fast inverse square root algorithm would either have no benefit or have so little that it isn't worth the extra lines of code or developer time associated with it.

If you want to draw graphics efficiently, be sure to use graphics technology like OpenGL or DirectX to run any per-pixel operations on the GPU. Fragment shaders on the GPU run in the order of 100's of times faster than equivalent code in CPU on a variety of computing devices from smart phones to desktops. Using the GPU properly makes a big performance improvement but the fast inverse square root estimate does not.