[Oberon] [OT] Re: System-7 - Math popular consts

[Liam Proven]

On Fri, 1 Mar 2019 at 13:41, Till Oliver Knoll
<till.oliver.knoll at gmail.com> wrote:

>
> IIRC that was a real „performance optimisation“ introduced by John Carmack in Doom, allowing for integer math in many places. And „circles were round enough“ that way ;) Not sure whether that is some urban myth though, since I could not find any reference at a glance...

I've not heard of that, but I recently came across this one:

https://medium.com/hard-mode/the-legendary-fast-inverse-square-root-e51fee3b49d9

http://ncannasse.fr/blog/fast_inverse_square_root

https://stackoverflow.com/questions/1349542/john-carmacks-unusual-fast-inverse-square-root-quake-iii

I've blogged in the past about how the optimisations in Quake were
Intel Pentium-specific and penalised the otherwise very capable and
quick Cyrix 6x86:

https://liam-on-linux.livejournal.com/49259.html

But there is some dispute -- see:

https://www.vogons.org/viewtopic.php?t=45815&p=461859

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