[clug] Code Search
Alex Satrapa
grail at goldweb.com.au
Sun Oct 8 23:33:43 GMT 2006
On 7 Oct 2006, at 14:00, Paul TBBle Hampson wrote:
> == Bad word follows... ==
>
> I particularly liked
> http://www.google.com/codesearch?...
> which caused me to learn about the method of approximating zeroes. ^_^
Approximating inverse square roots, even ;)
http://www.codemaestro.com/reviews/review00000105.html
I'm now twitching to find a problem I can solve with the magic number:
> The results are very surprising – Lomont's well calculated
> mathematically optimal constant [for the first approximation to the
> inverse square root of any number] turns out to be slighltly
> different (0x5f37642f) , and in spite of being theoretically
> better, it yields worse results then the original constant used in
> the source code!! Indeed, John Carmack must have used genuine black
> magic to find this number.
The funny thing is, you can find people commenting on the code
saying, "it's just a standard Newton-Raphson method" - totally
oblivious to the fact that the number John Carmack's code monkey
picked is better than what a mathematician found through mathematical
methods. Poor code monkey must have been looking for that number for
a long time.
Alex
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