Do you want to play a backgame or not?

ah....Clem

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Aug 13, 2022, 12:57:12 PM8/13/22

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Hint: I don't think Jacoby Beaver matters.

XGID=-a--BaC-AA--cD-a-c-dA-b-BA:0:0:1:52:0:0:3:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game, Jacoby Beaver
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X O X |
| X O | | O O X |
| X O | | O |
| X | | O |
| | X | |
| |BAR| |
| | | |
| | | |
| O | | X |
| O | | X X |
| O X X | | X O X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 188 O: 147 X-O: 0-0
Cube: 1
X to play 52

--
Ah....Clem
The future is fun, the future is fair.

Timothy Chow

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Aug 14, 2022, 9:25:59 AM8/14/22

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On 8/13/2022 12:57 PM, ah....Clem wrote:
>
> Hint: I don't think Jacoby Beaver matters.
>
> XGID=-a--BaC-AA--cD-a-c-dA-b-BA:0:0:1:52:0:0:3:0:10
>
> X:Player 1   O:Player 2
> Score is X:0 O:0. Unlimited Game, Jacoby Beaver
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X     O     O    |   | O X     O     X |
> | X           O    |   | O        O     X |
> | X           O    |   | O                |
> | X                |   | O                |
> |                  | X |                  |
> |                  |BAR|                  |
> |                  |   |                  |
> |                  |   |                  |
> | O                |   | X                |
> | O                |   | X     X          |
> | O        X X    |   | X O X        O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 188 O: 147 X-O: 0-0
> Cube: 1
> X to play 52

The question isn't whether X wants to play a backgame but whether
X feels the need to make a second anchor. But after bar/20 there
is no good 2 to play. I would hit, bar/23 20/15*.

---
Tim Chow

ah....Clem

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Aug 16, 2022, 9:25:22 AM8/16/22

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As Tim observes, it's not a backgame yet even when X makes the second
anchor. My thought was

"We enter with the five and create a backgame structure, but without the
timing of a backgame. But even in a proto-backgame pure play and
mobility are usually the right idea. So, bring one down - either we get
hit and gain timing or we solidify our blockade. 9/7 also looks
playable, but 13/11 looks stronger."

XG rollout agrees with entering with the five and also that 13/10 is
stronger than 9/7. But it likes the passive play of 8/6 that minimizes
shots. Presumably, this is because we're not committed to a backgame yet.

Interestingly, XGR++ reverses the order of second and third liking the
hit better than bar/20 13/10.

XGID=-a--BaC-AA--cD-a-c-dA-b-BA:0:0:1:52:0:0:3:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game, Jacoby Beaver
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X O X |
| X O | | O O X |
| X O | | O |
| X | | O |
| | X | |
| |BAR| |
| | | |
| | | |
| O | | X |
| O | | X X |
| O X X | | X O X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 188 O: 147 X-O: 0-0
Cube: 1
X to play 52

1. Rollout¹ Bar/20 8/6 eq:-0.267
Player: 45.22% (G:10.91% B:0.44%)
Opponent: 54.78% (G:19.28% B:1.50%)
Confidence: ±0.017 (-0.284..-0.250) - [81.4%]
Duration: 1 hour 21 minutes

2. Rollout¹ Bar/20 13/11 eq:-0.280 (-0.013)
Player: 46.24% (G:10.38% B:0.47%)
Opponent: 53.76% (G:22.74% B:2.11%)
Confidence: ±0.021 (-0.300..-0.259) - [16.8%]
Duration: 59 minutes 49 seconds

3. Rollout¹ Bar/23 20/15* eq:-0.292 (-0.025)
Player: 45.57% (G:11.74% B:0.58%)
Opponent: 54.43% (G:22.97% B:2.48%)
Confidence: ±0.019 (-0.311..-0.273) - [1.9%]
Duration: 1 hour 44 minutes

4. Rollout¹ Bar/20 9/7 eq:-0.315 (-0.048)
Player: 45.08% (G:9.54% B:0.40%)
Opponent: 54.92% (G:22.32% B:1.83%)
Confidence: ±0.020 (-0.335..-0.295) - [0.0%]
Duration: 1 hour 23 minutes

¹ 1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

Timothy Chow

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Aug 16, 2022, 9:14:07 PM8/16/22

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On 8/16/2022 9:25 AM, ah....Clem wrote:

> Interestingly, XGR++ reverses the order of second and third liking the
> hit better than bar/20 13/10.

There's a lot of variance left.

> Confidence: ±0.017 (-0.284..-0.250) - [81.4%]

> Confidence: ±0.021 (-0.300..-0.259) - [16.8%]

> Confidence: ±0.019 (-0.311..-0.273) - [1.9%]

> Confidence: ±0.020 (-0.335..-0.295) - [0.0%]

---
Tim Chow

ah....Clem

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Aug 17, 2022, 9:32:04 AM8/17/22

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Fair enough. My approach is that once I see a rollout that says the
plays are close I'm satisfied with that. My play is weak enough that
I'm not going to worry about differences of .02 or less. Unless it's
some regularly recurring position like openings or bearoffs.

Anyway, here's an extended rollout. Making the second anchor is the
right idea, and it's within the margin of error whether to bring one
down or safety the blot on the eight.

XGID=-a--BaC-AA--cD-a-c-dA-b-BA:0:0:1:52:0:0:3:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game, Jacoby Beaver
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X O X |
| X O | | O O X |
| X O | | O |
| X | | O |
| | X | |
| |BAR| |
| | | |
| | | |
| O | | X |
| O | | X X |
| O X X | | X O X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 188 O: 147 X-O: 0-0
Cube: 1
X to play 52

1. Rollout¹ Bar/20 8/6 eq:-0.269
Player: 45.05% (G:11.04% B:0.43%)
Opponent: 54.95% (G:19.31% B:1.49%)
Confidence: ±0.013 (-0.281..-0.256) - [94.8%]
Duration: 1 hour 31 minutes

2. Rollout¹ Bar/20 13/11 eq:-0.285 (-0.016)
Player: 46.14% (G:10.39% B:0.45%)
Opponent: 53.86% (G:22.75% B:2.09%)
Confidence: ±0.015 (-0.299..-0.270) - [5.2%]
Duration: 1 hour 10 minutes

3. Rollout¹ Bar/23 20/15* eq:-0.303 (-0.035)
Player: 45.50% (G:11.63% B:0.60%)
Opponent: 54.50% (G:22.87% B:2.50%)
Confidence: ±0.015 (-0.318..-0.288) - [0.0%]
Duration: 1 hour 54 minutes

4. Rollout¹ Bar/20 9/7 eq:-0.313 (-0.044)
Player: 45.10% (G:9.61% B:0.41%)
Opponent: 54.90% (G:22.32% B:1.76%)
Confidence: ±0.014 (-0.326..-0.299) - [0.0%]
Duration: 1 hour 33 minutes

¹ 2592 Games rolled with Variance Reduction.