[PATCH conductor] RM 3396: Complex provider selection algorithms (rev. 2)

Imre Farkas ifarkas at redhat.com
Fri Aug 17 09:45:10 UTC 2012


On 08/15/2012 05:24 PM, Jozef Zigmund wrote:
> On Thu, 2012-08-02 at 14:24 +0200, ifarkas at redhat.com wrote:
>> This revision includes:
>> - a new page where user can enable/disable strategies
>> - fixes to address Jan's and Jozef's findings during their review
>>
>
> ACK, you can pushed the patchset.
>
> As we discussed it's needed to fix ASAP instance variables in patchset
> according "Coding Guidelines" part Instance Variables. [1]
>
> Question at the end:
> Other story is discussion about probability distribution and throwing
> out the matches of selected provider accounts. As we weren't able to say
> exactly if it's ok or not, we'd like to ask community(the best some
> person who has good knowledge from this field) :)
>
> What's happened?
> We are using random match in two places when we are trying to run
> deployment. One of that match is thrown out because the calculated match
> is changed by new one in the final launch. The questions is if we are
> breaking probability distribution of the provider account's selection ?
>
> [1] -
> https://www.aeolusproject.org/redmine/projects/aeolus/wiki/Coding_Guidelines
>
> --
> Jozef
>

I created a simple script which you can run on current master branch. It 
runs a number of experiments in 2 ways:
- 1st: it is using all the number from the random generator
- 2nd: it randomly throws out some outputs of the random generator

Then it displays how many times each match have been picked. If you run 
the experiment you can see there's no significant difference whether we 
are throwing away some numbers of the random generator, or not.

Here's the source: https://gist.github.com/3377279

Why is that? I don't exactly know the mathematical proof for this, so 
maybe I am wrong here, but intuitively you can consider the following:
Each pick has the same probability distribution: x% to be picked as A, 
y% to be picked as B. No matter which subset do you examine, it is true 
for the whole subset that x% of the subset will be picked as A, and y% 
will be picked as B, because each and every item in the subset belong to 
the same probability distribution.

Any issue regarding the test, or comment/critique are more than welcomed!

Imre





More information about the aeolus-devel mailing list