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Rollout and discussion

Posted By: Timothy Chow
Date: Wednesday, 6 August 2014, at 5:28 p.m.

In Response To: Tempo hit? (Timothy Chow)

It would have been more honest to advertise this position as, "Revisiting New Ideas in Backgammon #10," but I figured that such a boring subject line wouldn't attract any mouse clicks. Before giving the rollout of my position, let me first show you the original position from Woolsey and Heinrich's book:





White is Player 2

score: 0
pip: 145
Unlimited Game
Jacoby
pip: 148
score: 0

Blue is Player 1
XGID=--aa--E-CB--bDa--bcc-b--A-:0:0:1:43:0:0:1:0:10
Blue to play 43

1.Rollout113/9 6/3* eq: -0.349
Player:
Opponent:		41.79% (G:11.17% B:0.53%)
58.21% (G:18.87% B:0.88%)		Conf.: ± 0.011 (-0.360...-0.338) - [100.0%]
Duration: 7 hours 12 minutes
2.Rollout124/20 6/3* eq: -0.384 (-0.036)
Player:
Opponent:		41.98% (G:10.48% B:0.59%)
58.02% (G:22.00% B:0.76%)		Conf.: ± 0.008 (-0.392...-0.377) - [0.0%]
Duration: 6 hours 18 minutes
3.Rollout113/10 6/2* eq: -0.393 (-0.045)
Player:
Opponent:		41.24% (G:10.88% B:0.50%)
58.76% (G:20.77% B:0.99%)		Conf.: ± 0.009 (-0.402...-0.385) - [0.0%]
Duration: 6 hours 34 minutes
1 2592 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves and cube decisions: 4-ply

eXtreme Gammon Version: 2.10

The only difference is that White has a checker on her 11pt (rather than on the 10pt as in my position). When I first saw this position, my play was 24/20 6/3*. New Ideas in Backgammon barely considers this play, dismissing it by saying that it sticks a checker where White wants to attack. I could accept that it wasn't the best play, but I just didn't believe that it could be dismissed as a candidate so easily. Blue would like to escape the back checker or perhaps anchor on the 20pt if White hits the new blot on his 3pt, and what better time is there to step up than when White is on the bar?

I turned to the back of the book and got another surprise: None of the players that they polled wanted to play 24/20 6/3*. However, I did notice that Jellyfish didn't think it was so bad; 24/20 6/3* was only 0.010 back, which was a much closer margin than almost all the other problems in the book. Also it seemed to be the DMP play. The XG rollout above widens the margin for money play, but XG still thinks that 24/20 6/3* is viable at DMP:





White is Player 2

score: 0
pip: 145
1 point match
pip: 148
score: 0

Blue is Player 1
XGID=--aa--E-CB--bDa--bcc-b--A-:0:0:1:43:0:0:0:1:10
Blue to play 43

1.Rollout124/20 6/3* eq: -0.161
Player:
Opponent:		41.94% (G:12.13% B:1.66%)
58.06% (G:23.67% B:3.29%)		Conf.: ± 0.002 (-0.163...-0.159) - [55.0%]
Duration: 2 hours 51 minutes
2.Rollout113/9 6/3* eq: -0.161 (0.000)
Player:
Opponent:		41.93% (G:12.44% B:1.49%)
58.07% (G:21.39% B:3.33%)		Conf.: ± 0.002 (-0.164...-0.159) - [45.0%]
Duration: 2 hours 44 minutes
3.Rollout213/10 6/2* eq: -0.181 (-0.020)
Player:
Opponent:		40.93% (G:13.15% B:1.79%)
59.07% (G:23.10% B:3.73%)		Conf.: ± 0.006 (-0.187...-0.176) - [0.0%]
Duration: 21 minutes 07 seconds
1 10368 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

2 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

Anyway, here's the rollout of the position I posted. Now White doesn't have a good 6 from the bar, and 24/20 edges out 13/9.

It's good to see from people's responses that I'm not the only one who thinks that 24/20 is a viable play. (Of course I didn't post the exact position from the book, but I didn't get the impression that any respondents would have immediately dismissed 24/20 if White's checker had been shifted back to the 11pt.)

Sorry for not rolling out more candidates. I'm pretty sure that they're not close, though.





White is Player 2

score: 0
pip: 144
Unlimited Game
pip: 148
score: 0

Blue is Player 1
XGID=--aa--E-CB--bD-a-bcc-b--A-:0:0:1:43:0:0:0:0:10
Blue to play 43

1.Rollout124/20 6/3* eq: -0.321
Player:
Opponent:		43.76% (G:10.35% B:0.53%)
56.24% (G:21.51% B:0.69%)		Conf.: ± 0.008 (-0.329...-0.313) - [99.4%]
Duration: 6 hours 08 minutes
2.Rollout113/9 6/3* eq: -0.335 (-0.014)
Player:
Opponent:		42.66% (G:10.62% B:0.50%)
57.34% (G:18.92% B:0.77%)		Conf.: ± 0.008 (-0.343...-0.328) - [0.6%]
Duration: 6 hours 15 minutes
1 2592 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves and cube decisions: 4-ply

eXtreme Gammon Version: 2.10

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