Risc System/6000

[Keith Bierman - SPD Advanced Languages]

In article <415 at peyote.cactus.org> woan at peyote.cactus.org (Ronald S. Woan) writes:

   you get a system at $650/SPEC or so. Why are SPECs the geometric mean rather
   than average by the way?

Because the arithmetic mean (the "average") isn't reasonable when
comparing different rates. I've done a writeup or two, but I've
misplaced my brain. Let it suffice to note that:

	time A
	..      vs  time (A+..+N)
	time N
	

and compute the average(s). With the arithmetic mean, the single
number is jerked up a lot by one big outlier. The harmonic mean
produces the same value, which is argued fair by the original
livermore loops report, and other folks ... but which turns out to
penalize a system for screwing up on one particular code by a lot. The
geometric mean falls somewhere between. 

When I do the algebra, I pick the harmonic mean. When I stare at
enough benchmark figures, the geometric mean seems more sensible.
Others get different results. I wasn't there for the SPEC meetings,
but I bet this was debated for a bit and decided along Mashey's lines.


--
Keith H. Bierman    |*My thoughts are my own. !! kbierman at Eng.Sun.COM
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