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Date: Sat, 22 Aug 2015 05:20:57 +0300
From: Solar Designer <>
Subject: Re: BENCHMARK_LENGTH bugs

On Fri, Aug 21, 2015 at 01:22:40PM +0800, Kai Zhao wrote:
> On Fri, Aug 21, 2015 at 11:17 AM, Solar Designer <> wrote:
> > On Fri, Aug 21, 2015 at 11:03:19AM +0800, Kai Zhao wrote:
> >> Could we define slow: whose speed is less than e.g. 1000K c/s ?
> >
> > As per the previous few messages, we shouldn't define slow for the
> > purpose of your current work.  Since this was merely correlation and we
> > already know counter-examples, we shouldn't focus on this aspect.
> > We should instead focus on whether the "Many salts" and "Only one salt"
> > benchmarks results are expected to be different or almost the same.
> The benchmark_length should be 0 if the speedup from "Only one salt"
> to "Many salts" is greater than 1%.


> Otherwise, it should be -1. Is this right?

Not exactly.  e.g. 0.5% is still significant enough that I'd like to see
it _if_ there are good reasons for this difference to exist.  So the
ultimate decision is based on our knowledge of what goes on under the
hood (the "overkill" detail I provided to you) rather than on the
difference between benchmarks on a given run.

In other words, if the difference is reliably greater than 1% then we
should run the two separate benchmarks and report their separate results.

If not, then our decision may vary on a case by case basis.  If the
difference is extremely small - like all reported digits are literally
the same - then we're very likely to want to mute the separate

All of the above is for salted hashes only.  For saltless, we obviously
must never run these separate benchmarks.


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