Author: Robert Hyatt
Date: 10:12:25 07/06/03
Go up one level in this thread
On July 05, 2003 at 10:17:38, Omid David Tabibi wrote:
>In Genesis I heavily use the abs() function, and so tried to optimize it.
>Instead of using the abs() function defined in <math.h>, I wrote the following
>fucntion:
>
>long abs(long x) {
> long y;
> y = x >> 31;
> return (x ^ y) - y;
>}
>
>Testing it using a profiler, I found out that my implementation is about twice
>slower than the math.h implementation of abs(). I haven't looked at the
>implementation in math.h, but I can't see how a more optimized version of abs()
>can be written.
>
>Any ideas?
#define abs(x) ((x<0) ? -x : x)
I think the compiler will do that about as well as anything can be done, if
you have a good compiler. No branch needed if it is optimized right.
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