Computer Dice

Forum Archive : Computer Dice

Jellyfish: Proof it doesn't cheat

From:   Gary Wong
Date:   22 July 1998
Subject:   Re: Seed/counter (was Re: Jellyfish...)
Google:   wtyatlra73.fsf@brigantine.CS.Arizona.EDU

I can prove that [Jellyfish] _doesn't_ cheat with only two assumptions.  If
it does cheat, then one of my assumptions must be wrong.  Please give me a
counterexample demonstrating which one is unjustified.  The assumtions are:

1) The dice rolls depend ONLY on the seed/counter and NOTHING else (not the
   board position; not the match score; not the phase of the moon).

2) The move Jellyfish selects is strictly that which is evaluated with
   the highest equity; the evaluation may depend on board position, cube
   value and position, match score, but NOTHING else (not the current or
   future dice, whether manual or computer generated; not what you ate
   for breakfast this morning; nothing).

If these assumptions are true, then you can see that the dice and moves are
utterly independent.  You can set the seed/counter to whatever you like at
the beginning of the game.  Any board position is just as likely to occur
in that game as it is in another game with random seed/counter values.
Jellyfish will play the same move in each case.  With some seed/counter
values, the subsequent rolls will be good for Jellyfish; with other values,
they won't.  But the dice cannot possibly affect the moves (by assumption
2), and the moves cannot possibly affect the dice (by assumption 1);
therefore Jellyfish does not cheat.

Assumptions 1) and 2) are both falsifiable.  I cannot prove them (that
would take an exhaustive search of the entire seed/counter/board
position space, which is far too large).  But I hypothesise that they
are true, and so far there has been absolutely no evidence to refute
either of them.  This has led me to believe that both assumptions are
correct.  I will continue to believe in their truth (from which
Jellyfish's honesty directly follows) until evidence is provided to
the contrary.

        Gary Wong, Department of Computer Science, University of Arizona
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Computer Dice

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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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