RE: random number generator oddity

Random number generators, use a seed number to generate pseudo random
numbers, if you and your colleague have the same seed then you will get the
same numbers.

That said if a number is truly random you have just as much chance of
receiving that number as any other number. So you colleague getting 3444
should have no effect on your random chance of getting 3444!!!

What is random....?

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Emily Smith
Sent: 04 December 2008 21:39
To: midrange-l@xxxxxxxxxxxx
Subject: random number generator oddity

List,

We have a program that uses 'rand' to generate random numbers. I call this
program requesting an eight byte number and receive a number 81239122. I
sign off, and a coworker signs onto my workstation he also calls the program
requesting an eight byte number, and also receives 81239122. He signs off, I
sign back on, run the same program and receive a completely different number
73449833. I sign off. He signs back on again calls the program and receives
81239712.

So we've been testing this for about an hour using different scenarios (one
of us signs in at the same workstation and calls the program then signs off
and the other signs on, we sign in at the same time to different
workstations and call the program simultaneously, one signs in at one
workstation calls the program and then signs off the other signs on to a
second workstation and calls the program etc.) multiple times. Sometimes, we
would each get a random number that was the same as the other. Other times
the numbers would be completely different. Still other times the first four
or six digits would be the same but the last two or four would be the same.
Could anyone shed any light as to how 'rand' works and why it doesn't seem
to truly generate a random number? Is there something wrong with the program
that uses 'rand' to generate the random number?

Here is the code of the program that generates the random number.
D Number S 99 varying
D Length S 2 0
D A S 4 0
D X S 4 0
D digit S 4 dim(16)
D GetRandom PR 10U 0 ExtProc('rand')
C *entry Plist
C parm number
C Eval length = %LEN(Number)
C Eval X = (length / 4) + 1
C Eval A = 1
C Do X
C Eval digit(a) = %CHAR(GetRandom)
C Eval A = A + 1
C Enddo
C eval number = %trimr(digit(1))
C + %trimr(digit(2))
C + %trimr(digit(3))
C + %trimr(digit(4))
C + %trimr(digit(5))
C + %trimr(digit(6))
C + %trimr(digit(7))
C + %trimr(digit(8))
C + %trimr(digit(9))
C + %trimr(digit(10))
C + %trimr(digit(11))
C + %trimr(digit(12))
C + %trimr(digit(13))
C + %trimr(digit(14))
C + %trimr(digit(15))
C + %trimr(digit(16))
C Return

Thanks for all feedback.



Emily Smith
Programmer/Analyst
Bank Data Services
(618)659-4550
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