Snowie

Forum Archive : Snowie

 Luck calculation

 From: Gregg Cattanach Address: gcattanach@prodigy.net Date: 1 December 1999 Subject: Re: Snowie Luck Rate (was: Re: Unusual game.) Forum: rec.games.backgammon Google: 824jpg\$3lgm\$1@newssvr04-int.news.prodigy.com

```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
http://gateway.to/backgammon
ICQ #2266410
gcattanach@prodigy.net
```

 Hobbyish  writes: ```There are a couple of important qualifications to the luck factor however: 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 6-6. ```

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### Snowie

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)
Snowie cube evaluation  (Kit Woolsey, Sept 2007)
Snowie vs GNU  (Stanley E. Richards+, Oct 2005)
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)
Terminology  (Alexander Nitschke, Sept 1998)
Using rollouts  (Michael J. Zehr+, Oct 1998)

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