[alicebot-archcomm] more random <random>
Dr. Richard S. Wallace
alicebot-archcomm@list.alicebot.org
Sun, 28 Apr 2002 12:20:10 -0700
Yep. That's called random selection without replacement.
The classic example is a shuffled deck of cards. After you choose the seven
of hearts, you cannot choose the seven of hearts again.
Rich
----- Original Message -----
From: "Noel Bush" <noel@alicebot.org>
To: "Alicebot and AIML Architecture Committee"
<alicebot-archcomm@list.alicebot.org>
Sent: Sunday, April 28, 2002 12:17 PM
Subject: Re: [alicebot-archcomm] more random <random>
> I'm always immediately ready to believe that I'm the stupidest person in
> the room, and that with every word out of my mouth I only add more
> evidence that I'm utterly incompetent to express any thought or
> opinion. But that doesn't stop me from hoping that someone with more
> expertise will come along and help give form to the formless, so to
> speak.
>
> Do you have a prediction, mystical intuition, rock-solid proof,
> anything, regarding something like "shuffle" and whether it's needed?
> People who are building various bots for different applications seem to
> be expressing a need. Can someone who has already picked up several
> statistics books provide some articulation to this need?
>
> On Sun, 2002-04-28 at 23:06, Dr. Richard S. Wallace wrote:
> > My suggestion is to pick up a statistics book.
> >
> > Rich
> >
> > ----- Original Message -----
> > From: "Noel Bush" <noel@alicebot.org>
> > To: "Alicebot and AIML Architecture Committee"
> > <alicebot-archcomm@list.alicebot.org>
> > Sent: Sunday, April 28, 2002 12:02 PM
> > Subject: Re: [alicebot-archcomm] more random <random>
> >
> >
> > > Thanks, John and Rich, for the informative replies.
> > >
> > > I guess my concern has to do with an unanswered requirement that seems
> > > to be lurking, not the nature of randomness itself. The point about
> > > never finding an even distribution in a small sample is definitely
> > > important. And it helps me to understand better the need for a
> > > variation on the <random> theme, as was recently discussed on the
> > > mailing list.
> > >
> > > As in,
> > >
> > > <shuffle>
> > > <li>One thing.</li>
> > > <li>Another thing.</li>
> > > <li>And so on.</li>
> > > </shuffle>
> > >
> > > In which one item is chosen each time, "randomly" (without further
> > > discussing what that is), and then the same element will not be chosen
> > > again in the same bot-user context until all elements from the
<shuffle>
> > > have been "used up".
> > >
> > > I think this meets a need for what people would tend to mislabel
> > > "random" (myself included). It could be that this function is even
more
> > > needed than an actual <random>, since people are actually seeking a
way
> > > to create "varied, not-so-repetitive" responses, not really something
> > > that corresponds to a mathematical definition of random.
> > >
> > > On Sun, 2002-04-28 at 20:30, John Foderaro wrote:
> > > >
> > > >
> > > > >> The problem is that if two different <random> elements are
> > > > >> imagined to each have an independent random "space", tying all of
> > their
> > > > >> choices to the same sequence of pseudo-random numbers really
throws a
> > > > >> wrench into the works.
> > > >
> > > > I know what you're saying but I don't think there is anything to
worry
> > > > about. Random number generators will produce a nice even
distribution
> > > > but only over a very large number of samples. If you're asking
> > > > for a random number between 0 and 4 (inclusive) and call random 5
> > > > times you almost certainly won't get each number chosen once.
> > > > And that's the correct result since the odds of that happening
> > > > if the random number generator were truly random is very small.
> > > >
> > > > I wrote little test program to show this:
> > > >
> > > > If I chose 5 random numbers I get one 2, two 3's and 2 4's.
> > > >
> > > > cl-user(31): (testit :count 5)
> > > > 0: 0 0.0d0
> > > > 1: 0 0.0d0
> > > > 2: 1 0.2d0
> > > > 3: 2 0.4d0
> > > > 4: 2 0.4d0
> > > >
> > > >
> > > > If I chose one million random numbers I get this distribution.
> > > > Now the distribution is very nice over the 5 possible numbers:
> > > >
> > > > cl-user(32): (testit :count 1000000)
> > > > 0: 199398 0.199398d0
> > > > 1: 199834 0.199834d0
> > > > 2: 200394 0.200394d0
> > > > 3: 200158 0.200158d0
> > > > 4: 200216 0.200216d0
> > > >
> > > >
> > > >
> > > > Suppose that after every 7th random number I obtain I call
> > > > the random number generator and throw away the value. This is
> > > > simulating the case of running another <random> tag with a
> > > > different number of elements.
> > > >
> > > > We still end up with a nice distribution:
> > > >
> > > > cl-user(34): (testit :count 1000000 :toss-out 7)
> > > > 0: 200119 0.200119d0
> > > > 1: 200194 0.200194d0
> > > > 2: 199914 0.199914d0
> > > > 3: 199833 0.199833d0
> > > > 4: 199940 0.19994d0
> > > >
> > > >
> > > > So I don't think there is any need to create multiple independent
> > > > random number sequences, one for each <random> tag.
> > > >
> > > >
> > > > --john foderaro
> > > >
> > > > ps. here's my test code
> > > >
> > > > (in-package :user)
> > > >
> > > > (defvar results (make-array 5))
> > > >
> > > > (defun testit (&key (count 10000) (toss-out 0))
> > > > (dotimes (i (length results)) (setf (svref results i) 0))
> > > >
> > > > (dotimes (i count)
> > > >
> > > > ; throw out a random result periodically
> > > > (if* (and (> toss-out 0)
> > > > (zerop (mod i toss-out)))
> > > > then (random (+ (length results) 4)))
> > > >
> > > > ; now collect some random info
> > > > (incf (svref results (random (length results)))))
> > > >
> > > > (dotimes (i (length results))
> > > > (format t "~d: ~d ~s~%"
> > > > i
> > > > (svref results i)
> > > > (/ (float (svref results i) 1.0d0) count)))
> > > > )
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