From: jacobs@cs.utah.edu (Steven R Jacobs)
Subject: Re: Card Machines.
In-reply-to: s8818037@spectrum.cs.unsw.oz.au's message of Thu, 13 Aug 1992 18:27:56 GMT
Organization: University of Utah CS Dept
	<1992Aug13.182756.9454@usage.csd.unsw.OZ.AU>
Date: 16 Aug 92 12:46:06

In article <1992Aug13.182756.9454@usage.csd.unsw.OZ.AU> s8818037@spectrum.cs.unsw.oz.au (Matthew James Leayr) writes:

>I'm brand new to this group, so forgive my ignorance.
>I'm not sure you have them overseas, (no doubt you do) but practically every
>hotel in Australia has "card machines", which are a type of video poker
>machine.
>
>Operation is fairly simple:
>You pay for credits at the bar, usually 20c each which are electronically
>placed on the selected machine. You can bet up to five credits at a time,
>and are dealt five cards like normal poker, from which you select the ones
>to keep.....
>When betting 1 credit for example, two pairs wins 1 credit,
>three of a kind wins 2 credits
>a straight 4 credits,
>and so on, up to a royal flush which wins 500 credits. 

These sounds pretty much like the video poker machines in US casinos, but
with different payoff schedules.

>When you win, you have the option of double or nothing by choosing either red
>or black cards. The win can be doubled a maximum of five times.

I've seen "double" options on several machines, but this is the first time
that I've heard of machines that offer the double option more than
once per win.  It might be possible to exploit this to the player's advantage
if the red/black draw is done without returning the "used" cards to
the deck.  For example, if you've seen 6 red cards and 2 black cards, you
might gain by choosing black for doubling.

>What puzzles me is how are these machines programmed??
>Are they set to give a certain return to the player?

I've always *assumed* that they play a random game, using a single deck
of cards, and that once a cards is seen it is not returned to the deck
until the start of the next game.  So far, I have seen no evidence to
contradict these assumptions.

>Does the computer know in advance, which cards are to be dealt next?

I've always assumed that the cards are drawn completely at random.

>If the program realises that it is paying out too much, can it correct
>this by just "bumming" the next few players?

Maybe, but I don't consider this likely.  The payout schedule (1 for high
pair, 2 for two pair, 3 for trips, etc.) can be adjusted the give the house
an adequate edge without any need for messing with the probabilities involved
in dealing the game.  But, without inside information on the software that
is in the machine's ROMS, it is impossible to say for sure.

>It seems to me that what we may think of as a fairly "random" game of chance
>could simply be an illusion created by the machine. BTW, these machines are 
>extremely addictive. I've watched people put every last cent into them.
>Also, they don't seem to pay out very much - this isn't helped by the fact
>that most players automatically press the "double" button EVERY time they
>win I guess

From your description of payouts, it sounds like these machines have a large
house edge.  If you'll tell me the exact payout for each final hand, I can
compute the house edge (assuming no wild cards are used).

>Another question: whats the chance that the programmers of the machines left
>some coded "trapdoor" in the machine to allow themselves to win ie. some
>intricate (?) key sequence which triggers a winning streak in the machine.
>I suppose the code would come under close scrutiny by government bodies when
>the machines are being manufactured, but this could probably be circumvented.
>A devious thought, I know.............

Entirely possible.  I heard recently of a mad scramble by the casinos to
upgrade ROMS in their video poker machines because somebody discovered a
way to make them pay off nicely for the players.  Details of this rumor
were pretty sketchy though, so that is all I really know about it.
--
Steve Jacobs  ({bellcore,hplabs,uunet}!utah-cs!jacobs, jacobs@cs.utah.edu)
"Never teach a card counter to sing.  It wastes your time and gets the card
 counter barred."
Newsgroups: rec.gambling