Celebrating 15 years in backgammon games

Backgammon Brain Busters #68

by Michael Strato
14 March 2006


Strategy Talk

Players of all levels are invited to share their view on these interesting positions that we came across while honing our backgammon skills in match play.

Is the computer program always right? As we have seen in the past, even the best programs get certain scenarios wrong while world class human players have a better grasp of these situations through the experience of years of play.

The "Brain Busters" series offers three new backgammon positions in each article, problems that we believe to be challenging and worthy of thought and discussion - please post your opinion on how you would play these positions in the forum thread below.

We will do their rollouts with Snowie 4 Pro and publish the results along with a new set of positions about once a week. Enjoy!

Note: See the rollouts results of all previous Brain Busters articles at this link.





Please give us your thoughts on these without the help of a bot.







Position 1:










Pip: 142
7 point match

Green-White:
Score 0-0
Pip: 145








Position 2:










Pip: 150
7 point match

Green-White:
Score 5-2
Pip: 176








Position 3: Green on roll, cube action?










Pip: 127
5 point match

Green-White:
Score 0-0
Pip: 122











WARNING! - ROLLOUTS


March 21, 2006: Here are the Snowie rollouts for the three positions above:







Position 1:










Pip: 142
7 point match

Green-White:
Score 0-0
Pip: 145

# PlyMoveEquity
1 R 13/9 2/1* -0.276
0.3% 12.0% 45.7% 54.3% 22.9% 1.0%
95% confidence interval:
- money cubeless eq.: -0.201 ±0.037.
Rollout settings:
Full rollout,
144 games (equiv. 5222 games),
played 3-ply (precise),
random seed, with race database.
2 R 9/5 6/5 -0.425 (-0.149)
0.8% 13.8% 43.7% 56.3% 30.5% 1.2%
95% confidence interval:
- money cubeless eq.: -0.296 ±0.049.
Rollout settings:
Full rollout,
144 games (equiv. 4033 games),
played 3-ply (precise),
random seed, with race database.
3 R 9/8 6/2 -0.535 (-0.259)
0.4% 10.5% 41.1% 58.9% 29.2% 0.7%
95% confidence interval:
- money cubeless eq.: -0.368 ±0.035.
Rollout settings:
Full rollout,
144 games (equiv. 5688 games),
played 3-ply (precise),
random seed, with race database.
4 3 13/8 -0.429 (-0.152)
0.6% 11.7% 42.8% 57.2% 28.7% 1.4%
Speed Parameter: Precise.
5 3 6/2 3/2 -0.525 (-0.249)
0.4% 9.8% 40.3% 59.7% 26.1% 0.9%
Speed Parameter: Fast.








Position 2:










Pip: 150
7 point match

Green-White:
Score 5-2
Pip: 176

# PlyMoveEquity
1 R 13/7(2) 11/5*(2) 0.608
1.3% 29.5% 66.8% 33.2% 7.5% 0.6%
95% confidence interval:
- money cubeless eq.: 0.563 ±0.028.
Rollout settings:
Full rollout,
288 games (equiv. 8498 games),
played 3-ply (precise),
random seed, with race database.
2 R 11/5*(2) 8/2(2) 0.588 (-0.020)
1.1% 32.7% 64.1% 35.9% 7.6% 0.5%
95% confidence interval:
- money cubeless eq.: 0.539 ±0.025.
Rollout settings:
Full rollout,
288 games (equiv. 10253 games),
played 3-ply (precise),
random seed, with race database.
3 R 24/18(2) 11/5*(2) 0.569 (-0.039)
0.7% 24.4% 66.8% 33.2% 6.0% 0.2%
95% confidence interval:
- money cubeless eq.: 0.525 ±0.024.
Rollout settings:
Full rollout,
288 games (equiv. 9589 games),
played 3-ply (precise),
random seed, with race database.
4 R 24/18 13/7 11/5*(2) 0.460 (-0.148)
0.4% 25.1% 64.7% 35.3% 7.9% 1.0%
95% confidence interval:
- money cubeless eq.: 0.460 ±0.046.
Rollout settings:
Full rollout,
144 games (equiv. 3881 games),
played 3-ply (precise),
random seed, with race database.
5 3 24/18 11/5*(2) 8/2 0.240 (-0.368)
1.1% 23.7% 58.5% 41.5% 10.7% 0.7%
Speed Parameter: Fast.








Position 3: Green on roll, cube action?










Pip: 127
5 point match

Green-White:
Score 0-0
Pip: 122

Cube action equity
Rollout Money equity: 0.824
2.3% 46.9% 71.4% 28.6% 9.2% 0.4%
95% confidence interval:
- money cubeless eq.: 0.824 ±0.017,
- live cube no redouble: 1.077 ±0.022,
- live cube redouble take: 1.286 ±0.037.
Rollout settings:
Full rollout,
648 games (equiv. 23785 games),
played 3-ply (precise), cube 3-ply,
random seed, with race database.
Evaluations
1. No redouble 1.058
2. Redouble, pass 1.000 (-0.058)
3. Redouble, take 1.299 (+0.241)
Proper cube action: Too good to redouble, pass19%
Live cube
1. No redouble 1.077
2. Redouble, pass 1.000 (-0.077)
3. Redouble, take 1.286 (+0.209)
Proper cube action: Too good to redouble, pass27%











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2.
Subject: Re: Backgammon Brain Busters #68
From: StarLight
Date: 18 Mar 2006 06:59 EST

1. 9/5 6/5 a la JK I do not find it close at all! 1. White has already buried 2 stones on the home ace point. 2. White has no spares anywhere, so shots are coming, and there is no ammo to attack blots in white's home board. 3. Many 6s are awkward for white, so now is the time to lock the famous 5 point.

2. At this score there is only one play: 11/5 x 2 (zzzzzzzzzzzzzzzzzzzzzzzzzz) 13/7 x 2 a. This isolates white's runner, and builds a 5 prime. b. No other play is so unwelcome by white. And white's 6s STINK! c.The gammon possibility is now very high, as white's LONE runner can never anchor. The second white blot can be picked off, but the GAMMON wins the match..

3.D/Drop With 2 more fat targets, and an inferior to green board, white must drop the cheap 1 point.

Starlight, out!

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Celebrating 15 years in backgammon games