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Subject: Re: question about importance of branchless code for speed

Author: Uri Blass

Date: 23:43:22 04/09/03

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On April 10, 2003 at 02:08:36, Tony Werten wrote:

>On April 09, 2003 at 11:11:01, Uri Blass wrote:
>
>>Supppose file1 and file2 are numbers between 0 and 7.
>>
>>Am I correct to assume that in general it is better to not to use
>>
>>int A[8];
>>If (file1<=file2) x+=A[file2-file1];
>
>Most modern compilers will do better with:
>
>bonus=0;
>if (file1>file2) bonus=A[file2-file1];
>x+=bonus;


Do you say that 3 lines are faster than one line?(I guess you mean file1<=file2
and not file1<file2 as you wrote in your next message)

In any case it is only an example
Practically I have a slightly different condition.

if (file1+1<file2)
>
>The 2nd line basicly forces the compiler to use a CMOV.

What does CMOV means?

Uri



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