Fun and frustration

Forum Archive : Fun and frustration

What are the chances?

From:   Pete
Date:   6 March 2003
Subject:   gnubg's wrist

Don't mean to cast ANY aspersions upon the rolling talents of any
robotic entities, but to lose this race against gnubg is downright

    Move number 60: X to play 42

      GNU Backgammon  Position ID: v20DIADbLAAAAA
                      Match ID   : QQlqAUAAAAAA
      +13-14-15-16-17-18------19-20-21-22-23-24-+     O: gnubg (Cube: 2)
      |                  |   |    O  O  O  O  O |     4 points
      |                  |   |    O  O  O  O  O |
      |                  |   |                O |
      |                  |   |                O |
      |                  |   |                6 |
     v|                  |BAR|                  |     11 point match
      |                  |   |                  | X
      |                  |   |                  | X
      |                  |   |                  | X
      |                  |   |    X     X  X  X | X   Rolled 42
      |          O       |   | X  X     X  X  X | XX  0 points
      +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: user
    Pip counts: O 50, X 28

    Rolled 42:*    6/off

After I bore a man off, gnubg rolled: 66, 11, 22, 51, and 44.
Nothing serious...

Gregg Cattanach  writes:

That is a pretty remarkable parlay.  The race is so hopeless that even with
a rollout Snowie shows it as 100% wins for X, so you must be WAY more than
1000 to 1 to win this one.

Of course, it didn't cheat, but it is a pretty good bad beat story :)


Douglas Zare  writes:

I think it is about 2000-1 after the 4-2, and perhaps slightly more
unlikely before the 4-2. An immediate 6-6 would give 0.5% winning chances,
an immediate 5-5 would give 0.4%, and an immediate 4-4 would give 0.2%, and
these add up to about one chance in 3200. I think the other ways to win add
up to at least half as much.

On FIBS, I won a match against Costello in which I needed to roll 3 working
sets while it failed to roll any double twice. I calculated the chance at
about 3000 to 1, but that wasn't too surprising, since my experience level
on FIBS was greater.

A less likely event from real life: In a side event at the Boston Open, my
opponent and I rolled the same number 8 times to try to start the game. The
chance of that happening for any particular game is about 1 in 1.7 million,
and I certainly haven't played that many games. Of course, that was neither
lucky nor unlucky.

Something to keep in mind with bad-luck stories from real life is that
there is a good chance that they get garbled and exaggerated. A player
complained that I had rolled 5 doubles in a row after only 4 of my last 5
rolls were doubles. Since it is about 20 times as likely to be able to make
that mistake, if you think there is one chance in 10 that a player would
make that mistake then 2/3 of the stories you hear would be wrong.

If anyone thinks that they have found a pattern in the Mersenne twister
rng, please test it carefully, and then let everyone know, rather than the

Douglas Zare
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Fun and frustration

A game brings you money  (Michael J. Zehr, Feb 1996) 
A story from my youth  (neilkaz, Aug 2008) 
Backgammon at 50  (Mary Hickey, July 2005)  [GammOnLine forum]
Backgammon by mail  (MelRae, Aug 1997) 
Backgammon haikus  (Phil Simborg, July 2004) 
Backgammon hustler  (Socks, Apr 2004) 
Backgammon laws  (Walt Swan, Dec 1999) 
Beginner's luck  (Paul Tanenbaum, May 1999) 
Characters we all know  (Alan Webb, Feb 1999) 
Choking under pressure  (Kevin Bastian, Dec 1997) 
Danish Championship semifinal match  (Daniel Murphy+, Nov 2004)  [GammOnLine forum]
Don't come looking for sympathy ...  (Ian Shaw, Nov 2004)  [GammOnLine forum]
"Good roll!"  (jfk+, Jan 1998) 
Hard luck story contest  (Einar Tryggvason, Apr 1996) 
"I resign"  (neilkaz, June 2011) 
Lonely checker's lament  (Luvrhino+, Aug 2001) 
Losing streaks  (Stanley E. Richards+, June 2006)  [GammOnLine forum]
Losing streaks  (Leo Bueno+, Nov 1999) 
Losing streaks  (Jim Peplow, July 1998) 
New Year's resolutions  (Alan Webb, Jan 2000) 
One-liners  (scuba, Jan 2007) 
Simborg's laws of backgammon  (NYCGuy, June 1997) 
Some learning humor  (Daniel Murphy, Aug 2011) 
Ten commandments of backgammon  (Morten Wang, Nov 1997) 
The square thing  (David B. Sandler, June 1996) 
Translation fun  (James Eibisch, Feb 1998) 
What are the chances?  (Pete+, Mar 2003) 
Wishing good luck  (Michel Tarragnat, Apr 2005) 

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