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SubjectRe: Interesting scheduling times - NOT
Date
Oliver Xymoron <oxymoron@waste.org>:
: > Well, this is a fine theory - and it was what I thought when I started
: > measuring things - but it's wrong in practice. If you take a suite of
: > tests, lmbench for example, and do a bunch of runs and scatter plot them
: > and stare at them you'll see patterns emerging. Now if the pattern was
: > that most run times clustered around the min, then my feeling is that
: > the min is the right number. Wherever they cluster up is the number I
: > wanted because that was the number mostly likely to be seen.
:
: Again, I agree that generally the average is the number that's
: interesting.

Average == mean
Median == point where half the values < and half the values are >

An average will /not/ give you what you want. The median will do it. Try
it - take a bunch of runs and plot mean, median, max, min and you'll see.

: But earlier you seemed to imply that the minimum is not
: generally a meaningful number, because they were way out on the tails of
: normal distributions.

Err, I never said that results follow a normal distribution. In fact,
I would probably be the person that says they don't - normal, gaussian,
whatever, real world results tend not follow them anywhere near as much
as the modeling folks would like you to believe.

And I didn't say that the min is meaningless, I said that it isn't always
representative. Feel free to take any benchmark and plot a bunch of runs
and look at them. After you do that for a while, the median starts to look
like a really good choice. At least it did for me.

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