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At a cable TV company that I worked at we used a random number to select a
customer account number on a monthly basis. The selected account won a free
month subscription. The selected number was checked against the delinquent,
employee and level of service tables prior to being accepted.
----- Original Message -----
From: <rob@dekko.com>
To: <RPG400-L@midrange.com>
Sent: Wednesday, April 25, 2001 2:32 PM
Subject: RE: Random Number in PRG: example
>
> But don't we first need to find out why a random number is needed in the
> first place? For example, shouldn't a UUID be used in many cases in which
> a random number is used? UUID is great for a key because it's guaranteed
> to be unique across systems. Check out the archives for UID in midrange-l
> and rpg400-l available at midrange.com.
> About the only thing I use a random number for is a password generator.
>
>
> Rob Berendt
>
> ==================
> Remember the Cole!
>
>
>
> Scott Klement
> <klemscot@klement To:
"'RPG400-L@midrange.com'" <RPG400-L@midrange.com>
> s.com> cc:
> Sent by: Subject: RE: Random
Number in PRG: example
> owner-rpg400-l@mi
> drange.com
>
>
> 04/25/01 10:30 AM
> Please respond to
> RPG400-L
>
>
>
>
>
>
>
> On Wed, 25 Apr 2001, DeLong, Eric wrote:
>
> > True, I added the time seed shortly after posting the example, and I too
> > realized that Hans' example was repeating sequences. It also occurs to
> me
> > that seeding by TIME (6.0) could be a bad idea is the program runs at
the
> > same time every night (scheduled job). It's not hard to imagine the same
> > seed value being used repeatedly...... perhaps something more random
like
> > milliseconds....
> >
> > > Caveat: every time you run this, you will get the same sequence of
> > > `random' numbers. To get more truly pseudo-random numbers, seed the
> > > generator with (say) the result of the TIME opcode.
>
> Call me a purist, but... time is about the LEAST random thing I can
> think of -- it follows a rather well-established pattern. :)
>
> It may be true that when I'm typing the command to run a program on my
> AS/400, I can't predict at what millisecond the program will run -- but
> if I were a computer program, or a job scheduler, etc, my program would
> run at a rather predictable time.
>
> Even if the time a job starts varies a little now, as computers get faster
> it'll become more and more consistent!
>
> Therefore, I like to stick elements from the JOB NUMBER and DATE into my
> seed as well as the milliseconds. (Actually, I use microseconds) This
> makes me feel better. :)
>
> Here's an example:
>
> H DFTACTGRP(*NO) ACTGRP(*NEW) BNDDIR('QC2LE')
>
> D rand PR 10I 0 extproc('rand')
>
> D srand PR extproc('srand')
> D seed 10U 0 value
>
> D gettimeofday PR ExtProc('gettimeofday')
> D timeval 8A
> D timezone 8A
>
> D timeval DS
> D tv_secs 10I 0
> D tv_usecs 10I 0
>
> D sds
> D JobNo 264 269
>
> D Junk S 8A
> D Epoch S Z
> INZ(z'1970-01-01-00.00.00.000000')
> D UTC S Z
> D Date S D
> D Micro S 6S 0
> D DateStr S 10A
> D MicroStr S 6A
> D Seed S 10U 0
> D SeedStr S 10A
>
> D num s 10I 0
> D i s 10I 0
>
>
> ** get current time
> c callp gettimeofday(timeval: junk)
>
> ** convert to a timestamp
> c Epoch adddur tv_secs:*S UTC
> c adddur tv_usecs:*MS UTC
>
> ** get date & microseconds in a char string:
> c move UTC Date
> c *ISO move Date DateStr
> c extrct UTC:*MS Micro
> c move Micro MicroStr
>
> ** make a seed
> C eval SeedStr = %subst(DateStr: 9: 1)
> c + %subst(MicroStr: 6: 1)
> c + %subst(JobNo: 6: 1)
> c + %subst(DateStr: 10: 1)
> c + %subst(MicroStr: 2: 1)
> c + %subst(JobNo: 5: 1)
> c + %subst(MicroStr: 1: 1)
> c + %subst(MicroStr: 3: 3)
> c move SeedStr Seed
>
> c callp srand(Seed)
>
> c for i = 1 to 10
> c eval num = rand
> c num dsply
> c endfor
>
> c eval *inlr = *on
>
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