Re: gaussian distribution pgbench

On Wed, Jul 2, 2014 at 6:05 PM, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> wrote:
>
> Hello Mitsumasa-san,
>
>> And I'm also interested in your "decile percents" output like under
>> followings,
>> decile percents: 39.6% 24.0% 14.6% 8.8% 5.4% 3.3% 2.0% 1.2% 0.7% 0.4%
>
>
> Sure, I'm really fine with that.
>
>
>> I think that it is easier than before. Sum of decile percents is just
>> 100%.
>
>
> That's a good property:-)
>
>> However, I don't prefer "highest/lowest percentage" because it will be
>> confused with decile percentage for users, and anyone cannot understand this
>> digits. 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?
>
>
> What else? People have ten fingers and like powers of 10, and are used to
> percents?
>
>
>> So I'd like to remove it if you like. It will be more simple.
>
>
> I think that for the exponential distribution it helps, especially for high
> threshold, to have the lowest/highest percent density. For low thresholds,
> the decile is also definitely useful. So I'm fine with both outputs as you
> have put them.
>
> I have just updated the wording so that it may be clearer:
>
> decile percents: 69.9% 21.0% 6.3% 1.9% 0.6% 0.2% 0.1% 0.0% 0.0% 0.0%
> probability of fist/last percent of the range: 11.3% 0.0%
>
>
>> Attached patch is fixed version, please confirm it.
>
>
> Attached a v15 which just fixes a typo and the above wording update. I'm
> validating it for committers.
>
>
>> #Of course, World Cup is being held now. I'm not hurry at all.
>
>
> I'm not a soccer kind of person, so it does not influence my
> availibility.:-)
>
>
> Suggested commit message:
>
> Add drawing random integers with a Gaussian or truncated exponentional
> distributions to pgbench.
>
> Test variants with these distributions are also provided and triggered
> with options "--gaussian=..." and "--exponential=...".

IIRC we've not reached consensus about whether we should support
such options in pgbench. Several hackers disagreed to support them.
OTOH, we've almost reached the consensus that supporting gaussian
and exponential options in \setrandom. So I think that you should
separate those two features into two patches, and we should apply
the \setrandom one first. Then we can discuss whether the other patch
should be applied or not.

Regards,

--
Fujii Masao