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Subject: Re: is the

Author: Dan Newman

Date: 11:30:47 07/20/98

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On July 20, 1998 at 13:35:50, Bruce Moreland wrote:

>I would like to ask you to do another test, if you could, since you have both
>versions available.
>Run your suite maybe 20 times, ten times with the old version, and ten times
>with the new version, but interleave them so that you alternate between the two,
>and do this via a batch file, so it is all as automatic as possible.
>What you should see is slow/fast/slow/fast/slow/fast etc.  What I am a little
>afraid you will see is slow/fast/fast/fast/fast/fast etc.

I think I've seen this priming-the-pump effect--though perhaps not as
pronounced as a 4% change in node rate.  Is it due to branch prediction
being pre-set by the first run or some sort of alignment variation?

One of the biggest effects I see is that I get a much larger node rate
the longer I run.  If I run a test for 10 s I might get 170 knps.  If
I run for 40 s 200 knps.  It does level off of course.  I'm using a
P6/200, so I've attributed this effect to improving branch prediction
as the code runs.  Any ideas?


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