Re: gaussian distribution pgbench -- splits v4
От | Fabien COELHO |
---|---|
Тема | Re: gaussian distribution pgbench -- splits v4 |
Дата | |
Msg-id | alpine.DEB.2.10.1407231828340.3626@sto обсуждение исходный текст |
Ответ на | Re: gaussian distribution pgbench -- part 1/2 (Robert Haas <robertmhaas@gmail.com>) |
Ответы |
Re: gaussian distribution pgbench -- splits v4
(Mitsumasa KONDO <kondo.mitsumasa@gmail.com>)
Re: gaussian distribution pgbench -- splits v4 (Robert Haas <robertmhaas@gmail.com>) |
Список | pgsql-hackers |
Hello Robert, > Some review comments: Thanks a lot for your return. Please find attached two new parts of the patch (A for setrandom extension, B for pgbench embedded test case extension). > 1. I suggest that getExponentialrand and getGaussianrand be renamed to > getExponentialRand and getGaussianRand. Done. It was named like that because "getrand" was used for the uniform case. > 2. I suggest that the code be changed so that the branch currently > labeled as /* uniform with extra argument */ become a hard error > instead of a warning. > > 3. Similarly, I suggest that the use of gaussian or uniform be an > error when argc < 6 OR argc > 6. I also suggest that the > parenthesized distribution type be dropped from the error message in > all cases. I wish to agree, but my interpretation of the previous code is that they were ignored before, so ISTM that we are stuck with keeping the same unfortunate behavior. > 4. This question mark seems like it should be a period: > > + * value fails the test? To be on the safe side, let us try over. Indeed. > 5. With regards to the following paragraph: > > <para> > + The default random distribution is uniform, that is all values in the > + range are drawn with equal probability. The gaussian and exponential > + options allow to change this default. The mandatory > + <replaceable>threshold</> double value controls the actual distribution > + with gaussian or exponential. > + </para> > > This paragraph needs a bit of copy-editing. Here's an attempt: "By > default, all values in the range are drawn with equal probability. > The <literal>gaussian</> and <literal>exponential</> options modify > this behavior; each requires a mandatory threshold which determines > the precise shape of the distribution." The following paragraph > should be changed to begin with "For a Gaussian distribution" and the > one after "For an exponential distribution". Ok. I've kept "uniform" in the first sentence, because this is both an option name and it is significant in term of probabilities. > 6. Overall, I think the documentation here looks much better now, but > I suggest adding one or two example to the Gaussian section. Like > this: for example, if threshold is 2.0, 68% of the values will fall in > the middle third of the interval; with a threshold of 3.0, 99.7% of > the values will fall in the middle third of the interval. These > numbers are fabricated, and the middle third of the interval might not > be the best part to talk about, but you get the idea (I hope). Done with threshold value 4.0 so I have a "middle quarter" and a "middle half". -- Fabien.
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