My guess, though, is that if he improved the performance, he used some other wizardry (Chebyshev or something similar).
If anything it's a lesson that the definition of brilliance is being in the wrong place at the wrong time... ;-)
These days I think the reciprocal square root intrinsic is the fastest where precision is not that important.
I think there was a bit twiddling hack for pop count which was consistently faster than the equivalent cpu intrinsic due to some weird pipelining effect, so sometimes it is possible to beat the compilers and intrinsics with clever hacks.
Check it out for yourself! I’m not claiming this was some kind of prodigious programming move, just something memorable that stuck with me.
> He also learned C++ in a weekend and was vastly better at it by the end of that weekend than most people I’ve met in industry
I doubt this. Really, really doubt this. Sure, geniuses exist, but I don't buy it.
The idea that someone who knows a high-level object-oriented language could translate that to immediate success in low-level C++ syntax at a level higher than the experts that developed the libraries over a weekend is frankly fantastical.
this is not synonymous with "most [C++ programmers] in industry"
The claim was the person learned it better than most people in industry, not most people writing the libraries upon which the industry is based
EDIT: Also we don't technically know when this happened. If this story is from the 1990s, it's a lot more likely, because think of how many shitty C++ programmers there were back then since we didn't have all the language options we do now. It was still the language taught in schools, for example. Then it was Java and Python and JS etc. But back then, Jonny Mackintosh was writing bad C++ out of uni.
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