Simple algorithm question - how to reorder a sequence economically

[Carlos Nepomuceno]

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> Date: Fri, 24 May 2013 12:01:35 -0700
> Subject: Re: Simple algorithm question - how to reorder a sequence economically
> From: peter.h.m.brooks at gmail.com
> To: python-list at python.org
>
> On May 24, 5:00 pm, Carlos Nepomuceno <carlosnepomuc... at outlook.com>
> wrote:
>>
>>
>> I don't know what "spurious evidence of correlation" is. Can you give a mathematical definition?
>>
> If I run the simulation with the same sequence, then, because event E1
> always comes before event E2, somebody might believe that there is a
> causative connection between them in the world that's being simulated,
> when, in fact, they only correlate in this way because the sequence is
> not being shuffled. That's what it means.

Correlation does not imply causation. If "somebody" is an expert system and you want to avoid it's recognition and/or triggering of some kind, and you can't or don't want to change it's behavior, you may take the random way because it's cheaper.

> Actually it'll be a bit more subtle than that, because each iteration
> of the simulation updates all nodes in one time interval, the events
> will not usually show the order of iteration - but, where there are
> any secondary effects, that are related to the order in which the
> nodes are updated, these will always happen the same way, which is my
> concern.

You should have a more precise understanding of the dependence of the variables you taking in consideration before randomizing the series of events your are using for tests.

I suggest you start using PPMCC. If it's close to zero or negative you wouldn't have to mind about it! ;)