From: "tim....." 
Newsgroups: uk.finance
Subject: Re: Premium Bonds
Date: Fri, 1 Jun 2007 18:22:38 +0100


"Ronald Raygun"  wrote in message 
news:_AS7i.29133$Ro3.13253@text.news.blueyonder.co.uk...
> Tiddy Ogg wrote:
>
>> On 31 May 2007 16:47:47 -0700, martynduerden@cwcom.net wrote:
>>
>>>it seems to me to be quite an important question
>>>
>>>When is the draw?????????
>> If they're still using the original ERNIE it probably takes all day.
>>
>> Even if not, it must take a while.  Picking thousands from millions is
>> different from picking 6 from 49.
>
> Well, sure it's different, but since it doesn't involve handling
> millions of physical balls in a huge tumble drier, it's really
> quite quick.
>
> And you don't need to generate random numbers in the space of all
> possible numbers, as JB said.  It is sufficient to know how many
> (and which) numbers are actually issued.  You simply make a list
> of the numbers issued, and if there are N numbers in that list, you
> can easily generate a random number in the interval [1..N].  Then
> you use the generated number as an index into your list, and Bob's
> your uncle.  Repeat N-1 times.  Most desktop PCs these days could
> do it in perhaps a microsecond per pick.

The system that is used generates numbers that include
the cashed in Bonds.

One month I got a little letter telling me that I had won
from the "reserve list" as one (or more) of the winning
list was a Bond that was no longer eligible.

tim