Author: Eugene Nalimov
Date: 14:17:18 02/14/02
Go up one level in this thread
Is it possible that by removing some code from your program you speed up the
remaining code? E.g. better cache locality, less information for branch
predictor to store (less conflicts), etc.?
Eugene
On February 14, 2002 at 16:54:32, martin fierz wrote:
>On February 14, 2002 at 02:42:53, Artem Pyatakov wrote:
>
>>Martin,
>>
>>I have used profiles successfully MANY times to find out which specific areas of
>>the program need optimization. What do you mean by "it just does not work"?
>>Also, kNPS does not tell you what is making the program slow - profiles often
>>do.
>>
>>Artem
>
>i mean what i say - the profiler is interfering so much with your program, that
>you cannot trust what it says. i recently programmed an endgame database builder
>for checkers and wanted to know if the positiontoindex or the indextoposition
>function is faster. i asked the profiler which told me that indextoposition is 8
>times faster.
>this profile was generated in a loop
>
>for(i=0;i<dbsize;i++)
> {
> indextoposition(...)
> positiontoindex(...)
> }
>
>the time to run this program without profiling was 17 seconds. when i took out
>the positiontoindex function of the loop, it took 13 seconds to run. since both
>functions are rather complex, and since there are no common parts of the two
>functions, it is clear that in fact, in the real program, positiontoindex is 3
>times faster. this is off by a factor of 24 compared to what the profiler says.
>since the second method is clearly measuring actual performance of my program, i
>have to conclude that the profiler is dead wrong.
>i guess it has something to do with the fact that positiontoindex calls some
>small subroutines, while indextoposition does not. this makes the
>positiontoindex routine seem slower in the profiling process than it actually is
>since the profiler tries to profile the subroutines too. just a guess...
>
>aloha
> martin
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