Re: why use pow(x, 2)?
Re: why use pow(x, 2)?
- Subject: Re: why use pow(x, 2)?
- From: Gregory Weston <email@hidden>
- Date: Mon, 02 Nov 2009 17:36:45 -0500
Luke the Hiesterman wrote:
On Nov 2, 2009, at 11:25 AM, Ed Wynne wrote:
That said, the original question is a good one. Using x*x instead of
pow(x,2) would be quite a bit faster, so except for clarity
reasons, there
isn't a good reason to use pow() in that case.
Would it really be that much faster? I don't know exactly how pow() is
implemented, but I assume it's basically just a loop of
multiplications, in which case it would basically be the same as x*x
in this case, since it would exit after the first iteration....
The idea that pow() is too slow to be acceptable for small integer
exponents is inherited knowledge. A *long* time ago it was the case
that the overhead of the function call dwarfed the math of such
operations *and* CPUs were slow enough that if you were doing a lot of
it and you cared about performance it made sense to do it longhand.
Since then we've gotten better and tremendously faster CPUs and better
compilers, but it's one of those things that some people just absorbed
as a True Fact.
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