Re: rand("state")

[Mike Miller]

On Wed, 15 Feb 2006, Paul Kienzle wrote:

> state(625) is the position in the sequence.
>
> If the state vector is shorter than 625 or the position value points 
> outside the array, then I mix up the array a bit to make sure that bad 
> states are avoid (e.g., all zeros is bad).  This is why you are getting 
> a different seed from rand("state") than you put in with 
> rand("state",x).
>
> Given
>
>   seeds = randint(100,1,1e9);
>   save seedfile seeds
>
> You can get a reproducible effecting using:
>
>   load seedfile
>   for s = seeds, sim(rand("state",seeds(i))); end
>
> You don't get any improvement in the randomness by using longer seeds.
>
> I've corrected the documentation so that it reports the state vector is 
> a row vector.  For compatibility it should be a string, but that is an 
> issue for another day.


That is interesting.  The one thing I don't understand is why there is a 
625-integer state if I get no improvement in randomness for using 625 
integers for the seed instead of a single integer.  I'm probably confusing 
"state" and "seed."  With a period of about 4.3*10^6001, I would think 
that using a seed that is always less than 10^9 would be allowing the user 
to access only a small minority of the random sequences available.

Mike



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