SBU calculations

Bruce Dubbs bdubbs at
Fri Jun 17 09:38:03 PDT 2005

Tushar Teredesai wrote:
> On 6/17/05, Steve Crosby <steve.crosby at> wrote:
>>  SBU's are a wild-ass guess. The methodology of calculating SBU's is fine,
>>but the application of someone else's build time measurements bear only
>>rough resemblance to my system - specifically because of architecture,
>>disk, memory, CPU cache differences etc. Do we really need to care about
>><10% variances in build times for the initial SBU, when you can get greater
>>variance than that due to other variables in the system.
>>(The point being, should we really care that much about how accurate the
>>SBU is, given it's a finger in the air, rough-guide anyway....)

> +1. My thoughts exactly, though I doubt if I could have said it so
> appropriately.

Even though it is an estimate for users, we should have a precise
methodology.  Giving SBUs to four or five significnat digits is not
appropriate, but giving our best approximation is.

If you check the SBU site main page, you will see in the numbers the
standard deviation of the submitted values.  In some cases, it is
obvious that the values are wildly divergent.  In other cases, they are
pretty good.

I recommend just establishing a policy and using it as specified.  The
details of the policy are not that important.  Documenting and following
the policy is important.

  -- Bruce

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