Author: Omid David Tabibi
Date: 11:05:03 07/06/03
Go up one level in this thread
On July 06, 2003 at 13:12:25, Robert Hyatt wrote:
>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.
What's the difference between the above macro and the function
int simple_abs (int i) {
return (i >= 0) ? i : -i;
}
when inlined?
Russel's test (http://talkchess.com/forums/1/message.html?304930) shows that
this simple_abs() is slow in comparison to various other abs implementations.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.