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From: brianc@billybob.demon.co.uk (Brian A Crawford)
Newsgroups: comp.lang.ada
Subject: Re: Pseudo Random coding problem
Date: Wed, 08 Jan 2003 10:57:54 GMT
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My intention was to produce one stream of pseudo random numbers
continuously one at a time (until say 10 billion trials) for a
simulation; look at that number produced; 
if it was a 20 then do one action, 
if it was a 5 or a 10 do another, 
if it was a 2, 4, 6, 8 do another. 
 
This is simplified somewhat.  I did it in the range of 1 to 50 and 15
trials just for debugging and checking code.  
The random range will be 1.. 1Million.
The number 20, 2, 5 etc aren't important; it was an easy way of
getting a probability of events happening.
E.g #2,4,6,8 coming up in 1 million numbers is 250K to 1 etc.

According to the replies so far I seem to be producing two streams.
How do I produce and check one only.

Many Thanks 
Brian

On Wed, 08 Jan 2003 01:55:07 GMT, tmoran@acm.org wrote:

>> sometimes sees the value 20 and on other occasions doesn't.
>
>You are generating 30 random integer from 1 ..  50 (15 from the
>"Ada.Integer_Text_IO.Put" and another 15 from the
>"if Random_50.Random(Gen => G) = 20 then").  The probability that
>none of those is a 20 is (49/50)**30 = 0.55   If the 20 should come
>up on the "Ada.Integer_Text_IO.Put" you will see it printed
>out.  Since those are half of the 30 calls, you ought to see "20"
>printed about 0.27 of the time.  If the 20 comes up on the
>"if" statement instead, you won't see a 20 at all, but will instead
>see "Random Number is equal to Twenty".  That also should happen
>on about 27% of the runs.  Running your program 100 times, a quarter
>second apart (to let the random generator start differently), I
>see 26 of the runs output "Random Number is equal to Twenty" at
>least once.  Sounds just about right.