More problems with random seed (was Re: whrandom seed question)

Al Christians achrist at easystreet.com
Wed Nov 24 22:20:59 CET 1999


Stelios Kyriacou wrote:
> 
> Why when I call the gauss distribution I get 2 alternating values:
> 
> >>> random.seed(0); print random.gauss(0,1);
> 2.11224018067
> >>> random.seed(0); print random.gauss(0,1);
> 0.225551631579
> >>> random.seed(0); print random.gauss(0,1);
> 2.11224018067
> >>> random.seed(0); print random.gauss(0,1);
> 0.225551631579
> >>> random.seed(0); print random.gauss(0,1);
> 2.11224018067
> >>>
> 
> Any more ideas?


Surprisingly:

>>> random.seed(0)
>>> random.gauss(0,1) / random.gauss(0,1)

Gives me either 0.106783136522 or 9.36477455684

And, astoundingly (???):

>>> 9.36477455684 * 0.106783136522
1.0

Not really, according to Numerical Recipes, etc, random gaussian's are 
generated in pairs.  One is saved for next time.  The random.seed() 
function must not be clearing out the cached value.

Should it?

Al




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