Re: gaussian distribution pgbench - Mailing list pgsql-hackers

<div class="moz-cite-prefix">On 02/07/14 21:05, Fabien COELHO wrote:<br /></div><blockquote
cite="mid:alpine.DEB.2.10.1407021046080.22369@sto"type="cite"><br /> Hello Mitsumasa-san, <br /><br /><blockquote
type="cite">AndI'm also interested in your "decile percents" output like under <br /> followings, <br /> decile
percents:39.6% 24.0% 14.6% 8.8% 5.4% 3.3% 2.0% 1.2% 0.7% 0.4% <br /></blockquote><br /> Sure, I'm really fine with
that.<br /><br /><blockquote type="cite">I think that it is easier than before. Sum of decile percents is just 100%.
<br/></blockquote><br /> That's a good property:-) <br /><br /><blockquote type="cite">However, I don't prefer
"highest/lowestpercentage" because it will be confused with decile percentage for users, and anyone cannot understand
thisdigits. I cannot understand "4.9%, 0.0%" when I see the first time. Then, I checked the source code, I understood
it:(It's not good design... #Why this parameter use 100? <br /></blockquote><br /> What else? People have ten fingers
andlike powers of 10, and are used to percents? <br /><br /><blockquote type="cite">So I'd like to remove it if you
like.It will be more simple. <br /></blockquote><br /> I think that for the exponential distribution it helps,
especiallyfor high threshold, to have the lowest/highest percent density. For low thresholds, the decile is also
definitelyuseful. So I'm fine with both outputs as you have put them. <br /><br /> I have just updated the wording so
thatit may be clearer: <br /><br />  decile percents: 69.9% 21.0% 6.3% 1.9% 0.6% 0.2% 0.1% 0.0% 0.0% 0.0% <br />
 probabilityof fist/last percent of the range: 11.3% 0.0% <br /><br /><blockquote type="cite">Attached patch is fixed
version,please confirm it. <br /></blockquote><br /> Attached a v15 which just fixes a typo and the above wording
update.I'm validating it for committers. <br /><br /><blockquote type="cite">#Of course, World Cup is being held now.
I'mnot hurry at all. <br /></blockquote><br /> I'm not a soccer kind of person, so it does not influence my
availibility.:-)<br /><br /><br /> Suggested commit message: <br /><br /> Add drawing random integers with a Gaussian
ortruncated exponentional distributions to pgbench. <br /><br /> Test variants with these distributions are also
providedand triggered <br /> with options "--gaussian=..." and "--exponential=...". <br /><br /><br /> Have a nice
day/night,<br /><br /><br /><fieldset class="mimeAttachmentHeader"></fieldset><br /><pre wrap="">
 
</pre></blockquote> I would suggest that probabilities should NEVER be expressed in percentages! As a percentage
probabilitylooks weird, and is never used for serious statistical work - in my experience at least.<br /><br /> I think
probabilitiesshould be expressed in the range 0 ... 1 - i.e. 0.35 rather than 35%.<br /><br /><br /> Cheers,<br />
Gavin<br/>