Forum Archive : Snowie

Luck calculation

From:   Gregg Cattanach
Date:   1 December 1999
Subject:   Re: Snowie Luck Rate (was: Re: Unusual game.)
Google:   824jpg$3lgm$

The luck factor calculated by Snowie works this way.  It calculates the
resulting equity of the 36 rolls, assuming each is moved 'correctly'.   It
then subtracts the equity resulting from the roll that was rolled from this
average.  A negative results is an 'unlucky' roll, a positive number is a
'lucky' roll.  This is accumulated for each game, and the result is shown
and reported.  All good luck for one person is counted as bad luck for the
other, so it is a zero sum result.

Gregg Cattanach
Zox at GamesGrid, VOG, Zone
ICQ #2266410

Hobbyish  writes:

There are a couple of important qualifications to the luck factor

1. They are cube-independent.  A lucky roll with the cube on 8 is not
given greater weight than an equally lucky roll with the cube on 1.

2. They are cubeless.  To me, the "luckiest" roll in most cases is the
roll my opponent gets that lets me offer an efficient double.  If my
opponent's equity on a given roll goes from, say, -.55 to -.75, he
will be assigned negative luck, when in fact it really did me no good
at all - I went from an optimally efficient double to a pass.

3. They are gammon-dependent.  If you play shorter matches you will
have a greater proportion of games where gammons do not count for one
side or the other.  In the limiting case, suppose you played only
one-point matches.  All the luck factors would be smaller since
gammons don't count.

4. This is perhaps more a case of asking how many angels can dance on
the head of a pin - but - consider the following:

Trailing 160-148 in a non-contact position you roll 6-6.  Your
pre-move equity was (in the position I chose to set up) about -.20,
after the roll is is about +.32.  The roll was lucky by .52.

You have a checker on the 5 and one on the 2, your opponent has one on
the ace.  Your pre-roll equity is .056.  Your luck factor on the next
roll will be either +.944 or -1.056.

Somehow, I personally feel that if I roll 6-6 in a race, that ought to
be the "luckiest" roll of the race, not the final roll on which I do
or don't get off to win.  If I roll 6-6 and reach the 5-2 position,
well, I would never have even gotten to that if I hadn't rolled the
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Announcement  (Olivier Egger, Apr 1998) 
Checker-play-according-to-score bug  (Peter Schneider+, June 2001) 
Error rates  (Gregg Cattanach, Oct 2000) 
Hints and questions  (Achim Müller+, Aug 1998) 
Luck calculation  (Gregg Cattanach+, Dec 1999) 
Questions and answers  (David Montgomery, Dec 1998) 
Running in low priority  (lmfback+, Oct 2004) 
Snowie 4.0  (SnowieGroup Info, Oct 2002) 
Snowie 4.3 update  (Gregg Cattanach, July 2005)  [GammOnLine forum]
Snowie cube evaluation  (Kit Woolsey, Sept 2007)  [GammOnLine forum]
Snowie vs GNU  (Stanley E. Richards+, Oct 2005)  [GammOnLine forum]
Snowie vs. Jellyfish  (Mark Driver, Apr 2001) 
Snowie vs. Jellyfish  (Daniel Murphy, Oct 2000) 
Snowie vs. Jellyfish  (Gregg Cattanach+, Sept 2000) 
Snowie vs. Jellyfish  (Wayne Crookes, Jan 1999) 
Snowie vs. Jellyfish  (Kenneth M. Arnold+, May 1998)  [Long message]
Terminology  (Alexander Nitschke, Sept 1998) 
Using rollouts  (Michael J. Zehr+, Oct 1998)  [Long message]

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