Computer Dice

Forum Archive : Computer Dice

Does MVP Backgammon cheat?

From:   Mark Betz
Date:   28 October 1996
Subject:   Re: MVP Backgammon question
Google:   01bbc507$505521a0$a21b12cf@mariner

Armin wrote:
> I bought a copy of a shareware game called MVP Backgammon and I'm
> wondering if anyone has had any experience with it.
> It seems to me that the rolls are not very random.

Art Buell wrote:
> I bought the same program, and I certainly agree.  I know the tendency
> is to subjectively blame the dice, especially with computer programs, but
> I'm convinced that MVP is definitely biased in its rolls.  Multiple high
> doubles in a running game or when bearing off, hail mary combo shots off
> the bar, leaving me stuck on the bar routinely for 5 or 6 rolls with a
> 3-point board--all these are routine, especially once the cube is
> activated.
>   The worst feature, and one that's NOT subjective, is that if you do get
> the computer into a Crawford situation, say I go up 6-3 in a 7-pointer,
> and the computer wins that game, it doubles in the next game BEFORE you
> get to see its opening roll!!  The roll is made, but it's hidden from
> view until you either blindly accept the double or resign.  Very bad
> feature. I'm ready to give up on this program.

Hi, Art. I'm the author of MVP Backgammon, and I'd like to respond to your
points. I'll take the rolls issue first.

It is possible that the random algorithm used in MVP Backgammon is less
than ideal. I think it's a pretty good scheme, and I'll describe it in a
moment, but the key point is that is is _flatly impossible_ for my program
to bias its rolls in favor of the computer.

The dice engine is a server to the player objects. It has no knowledge of
whether the player object requesting a roll is a computer or human player.
In fact the distinction between human and computer players is invisible in
90% of this 50k line program.

The dice engine is contained in dtimer.dll, which is located in the program
directory. At startup this module creates two medium speed timers using the
multimedia hardware timer services. These timers "roll each die" in the
background about 18 times per second using a standard Borland RTL
pseudorandom number generator. When a player object (computer or human)
needs a roll it calls a method implemented in dtimer.dll which samples the
"roll stream" to obtain a value for each die.

I'd like to make it perfectly clear: the AI in MVP Backgammon does not
cheat; it has no invisible advantages over the human player, and in fact
the game is carefully architected so that all types of players are
subjected to the same constraints, and operate off of the same information
about the game context. In fact the AI is at a decided disadvantage
compared to the human player, as it knows nothing about the game history,
its opponent's history, or strategy, other than what is evidenced in a
single board position. Anyone caring to verify this independently may
contact me, and we can arrange for code to be examined.

On the issue of the operation of the game when the Crawford rule is enabed:
as Phil has pointed out the nature of doubles is that you offer them prior
to rolling. However, I confess that I am a much better programmer than
backgammon player. I implemented the Crawford and Jacoby rules according to
the best information I could get. My sources included Magriel's
"Backgammon", as well as Marc Ringuette, who worked on the AI with me, and
the beta testers in the MVPSOFT forum on Compuserve. I've relied on users
to verify the behavior, and to date noone has written to say that it is not
working properly. If there is a problem with the implementation of either
rule I hope someone here will be kind enough to make me aware of it. I am
about to release version 1.3 and would like to implement as many fixes as

Thanks for your thoughts.

Mark Betz
(Author of MVP Backgammon)
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Computer Dice

Dice on backgammon servers  (Hank Youngerman, July 2001) 
Does Agushak Backgammon cheat?  (Mr Nabutovsky, June 2000) 
Does BG by George cheat?  (George Sutty, Nov 1995) 
Does Backgammon NJ cheat?  (Greg+, June 2010) 
Does Cybergammon cheat?  (Goto Informatique, Aug 1996) 
Does David's Backgammon cheat?  (Joseph B. Calderone, June 1998) 
Does GNU Backgammon cheat?  (Robert-Jan Veldhuizen, Nov 2002) 
Does Gammontool cheat?  (Jim Hurley, Sept 1991) 
Does Hyper-Gammon cheat?  (ZZyzx, June 1996) 
Does Jellyfish cheat?  (Fredrik Dahl, June 1997) 
Does MVP Backgammon cheat?  (Mark Betz, Oct 1996) 
Does MonteCarlo cheat?  (Matt Reklaitis, June 1998) 
Does Motif cheat?  (Rick Kiesau+, Mar 2004)  [Long message]
Does Motif cheat?  (Billie Patterson, Feb 2003) 
Does Motif cheat?  (Robert D. Johnson, Oct 1996) 
Does Snowie cheat?  (André Nicoulin, Sept 1998) 
Does TD-Gammon cheat?  (Gerry Tesauro, Feb 1997) 
Error rates with computer dice  (NoChinDeluxe+, Feb 2011) 
FIBS: Analysis of 10 million rolls  (Stephen Turner, Apr 1997)  [Recommended reading]
FIBS: Are the dice biased?  (Kit Woolsey, Oct 1996) 
FIBS: Entering from the bar  (Tom Keith+, Apr 1997) 
GamesGrid: Too many jokers?  (Gregg Cattanach, Sept 2001) 
GridGammon: Are the dice random?  (leobueno+, Sept 2011) 
Jellyfish: How to check the dice  (John Goodwin, May 1998)  [Recommended reading]
Jellyfish: Proof it doesn't cheat  (Gary Wong, July 1998) 
MSN Zone: Security flaw  (happyjuggler0, June 2004) 
Official complaint form  (Gary Wong, June 1998)  [Recommended reading]
Randomness testing  (Brett Meyer+, Dec 2010) 
Safe Harbor Games dice  (Michael Petch+, Aug 2011) 
Synopsis of "cheating" postings  (Ray Karmo, Feb 2002) 
Testing for bias  (Kit Woolsey, Jan 1995) 
The dice sure seem unfair!  (Michael Sullivan, Apr 2004) 
Too many repeated rolls?  (Stephen Turner, Mar 1994) 
Winning and losing streaks  (Daniel Murphy, Mar 1998) 

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