Re: [ANNOUNCE] Interbench v0.20 - Interactivity benchmark

From: David Lang
Date: Wed Jul 13 2005 - 19:36:07 EST


On Thu, 14 Jul 2005, Con Kolivas wrote:

On Thu, 14 Jul 2005 03:54, Bill Davidsen wrote:
Con Kolivas wrote:
On Tue, 12 Jul 2005 21:57, David Lang wrote:
for audio and video this would seem to be a fairly simple scaleing factor
(or just doing a fixed amount of work rather then a fixed percentage of
the CPU worth of work), however for X it is probably much more
complicated (is the X load really linearly random in how much work it
does, or is it weighted towards small amounts with occasional large
amounts hitting? I would guess that at least beyond a certin point the
liklyhood of that much work being needed would be lower)

Actually I don't disagree. What I mean by hardware changes is more along
the lines of changing the hard disk type in the same setup. That's what I
mean by careful with the benchmarking. Taking the results from an athlon
XP and comparing it to an altix is silly for example.

I'm going to cautiously disagree. If the CPU needed was scaled so it
represented a fixed number of cycles (operations, work units) then the
effect of faster CPU would be shown. And the total power of all attached
CPUs should be taken into account, using HT or SMP does have an effect
of feel.

That is rather hard to do because each architecture's interpretation of fixed
number of cycles is different and this doesn't represent their speed in the
real world. The calculation when interbench is first run to see how many
"loops per ms" took quite a bit of effort to find just how many loops each
different cpu would do per ms and then find a way to make that not change
through compiler optimised code. The "loops per ms" parameter did not end up
being proportional to cpu Mhz except on the same cpu type.

right, but the amount of cpu required to do a specific task will also vary significantly between CPU families for the same task as well. as long as the loops don't get optimized away by the compiler I think you can setup some loops to do the same work on each CPU, even if they take significantly different amounts of time (as an off-the-wall, obviously untested example you could make your 'loop' be a calculation of Pi and for the 'audio' test you compute the first 100 digits, for the video test you compute the first 1000 digits, and for the X test you compute a random number of digits between 10 and 10000)

David Lang

--
There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies.
-- C.A.R. Hoare
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