# [Tutor] How trustworthy are pseudo-random numbers?

Andre Engels andreengels at gmail.com
Fri Oct 3 17:44:53 CEST 2008

```On Fri, Oct 3, 2008 at 5:32 PM, Andre Engels <andreengels at gmail.com> wrote:
> On Fri, Oct 3, 2008 at 5:25 PM, Luke Paireepinart
> <rabidpoobear at gmail.com> wrote:
>> Is your math correct?  That's ridiculously large.
>
> 1 year equals 3600 * 24 * 365 makes about 3*10^8 seconds.
> The universe is about 15.000.000.000 years old, that's about 5*10^17 seconds.
> With 1 billion combinations per second, each computer does 5*10^26
> combinations in that time.
> There are something like 10^70 or 10^72 particles in the universe,
> thus N is about 10^100, give or take a factor of thousand or so.
> N2 is equal to 5*10^17 * N * N, which we will round up to 10^220.
> N3 by that same calculation will be about 10^460.
> The unnamed last number that way becomes something like 10^940 (in
> reality, because of all the rounding up, more like 10^930). That's
> less than 1/10^600 of 10^1600 - I'd say that's dwarved by any
> definition of the word.

Oh, wait, I had to compare to 10^6001 instead of 10^1600... Which
means I could have gone on to N6 instead of N4.

>> On Fri, Oct 3, 2008 at 10:03 AM, Andre Engels <andreengels at gmail.com> wrote:
>>> On Fri, Oct 3, 2008 at 4:11 PM, Daniele <d.conca at gmail.com> wrote:
>>>> >From here
>>>> http://en.wikipedia.org/wiki/Pseudorandom_number_generator#Periodicity
>>>> and here
>>>>
>>>> I think it can be argued that the randomness is pretty trustworthy :o)
>>>
>>> Nice understatement on that last page - "most applications do not
>>> require 2^19937 unique combinations (2^19937 is approximately 4.315425
>>> × 10^6001)."
>>>
>>> If you used every atom in the known universe as a computer, then let
>>> them turn out a billion combinations a second for the entire time
>>> since the big bang, and call the number of combination you get then
>>> N...
>>> then take N computers turning out N combinations a second for the
>>> entire time since the big bang, and call the number of combinations
>>> they turn out N2...
>>> then take N2 computers turning out N2 combinations a second and call
>>> the number of combination they turn out in the time since the big bang
>>> and call that N3...
>>> then the number of combinations turned out by N3 computers turning out
>>> N3 combinations per second in the time since the big bang STILL
>>> dwarves in comparison to that number.
>>>
>>>
>>> --
>>> André Engels, andreengels at gmail.com
>>> _______________________________________________
>>> Tutor maillist  -  Tutor at python.org
>>> http://mail.python.org/mailman/listinfo/tutor
>>>
>>
>
>
>
> --
> André Engels, andreengels at gmail.com
>

--
André Engels, andreengels at gmail.com
```