Re: Still bug in Random
- To: mathgroup at smc.vnet.net
- Subject: [mg61777] Re: Still bug in Random
- From: Joseph Gwinn <JoeGwinn at comcast.net>
- Date: Sat, 29 Oct 2005 01:32:43 -0400 (EDT)
- References: <djsk93$8lr$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <djsk93$8lr$1 at smc.vnet.net>,
"Pedrob P.B. de Oliveira" <pedrob at mackenzie.br> wrote:
> I've just tried Mathematica 5.2 in respect to an old bug in Random[ ], as
> pointed out in the Mathgroup posting
>
> Subject: [mg61777] bug in Random
> From: Veit Elser <ve10 at cornell.edu>
To: mathgroup at smc.vnet.net
>
> and the bad news is that the bug remains...
>
> The problem is a correlation in the random numbers generated from running
> the expressions
>
> r=Table[Random[Integer,{1,2^62}],{10^5}];
> Union[Table[r[[i]]+r[[i+24]]-r[[i+20]],{i,10^5-24}]]
>
> which, surprisingly, yields simply
>
> {-2147483647, 1, 2147483649, 4611686016279904256,4611686018427387904,
> 4611686020574871552}
I wonder if the integer range of Random[] really supports integers
larger than 32 bits. If not, a random integer on the range 0..2^62 may
not be very random.
If you really do need 62-bit integers, it may work better to make them
from two 32-bit random integers.
Joe Gwinn