[wzdd]

Simply compiling it with -O3 produces something which completes in half the time of the JavaScript version (350ms for C, 750ms for JS), so perhaps that.

Edit for Twirrim: on this system (Ryzen 7, gcc 11): "-O3": 350ms; "-O3 -march=native": 208ms; "-O2": 998ms; "-O2 -march=native": 1040ms.

Edit 2: Interestingly, changing the C from float to double produces a 3.5x speedup, taking the time elapsed (with "-O3 -march=native") to 58ms, or about 12x faster than JS. This also makes what it's computing closer to the JavaScript version.

[Twirrim]

For fun and frolics:

No flags: 1843ms

-march=native: 2183 ms

-O2: 423 ms

-O2 -march=native: 250 ms

-O3: 425 ms

-O3 -march=native: 255 ms

O3 doesn't seem to be helping in my case.

[Tadpole9181]

They didn't use any optimization flags.

[Twirrim]

Yeah, I was just trying to show the difference. Doing it without optimisation flags is an utterly bewildering decision by the author.

[nickpsecurity]

Especially given the goal was increasing performance.

[jasonjmcghee]

Seems crazy to me that double would produce that kind of speed up. Is float getting emulated somehow? Don't they end up the same size?

[jlarocco]

> Don't they end up the same size?

No. Float is half the size of double.

[suby]

My intuition would have been that floats were faster because of this. Less memory to iterate through.

[fartsucker69]

it is faster in just about every way. less memory, even the cpu instructions (which are usually not the problem) are faster. there's something fucky going on with code gen here. or it could also simply be the measurement procedure that is doing something weird like working with not properly cold or equally warmed up data or instruction caches.

[anon946]

Did you add output of the results to the C code?

[wzdd]

I did not, but I confirmed with objdump that my compiler was not removing the code.

(But to be sure, I just ran it again with an output and got the same value.)