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interests / rec.games.backgammon / Time to break anchor? 2

SubjectAuthor
* Time to break anchor? 2Timothy Chow
+* Re: Time to break anchor? 2ah...Clem
|`- Re: Time to break anchor? 2Timothy Chow
`- Rollout: Time to break anchor? 2Timothy Chow

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Time to break anchor? 2

<uj56id$29lqo$2@dont-email.me>

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Time to break anchor? 2
Date: Thu, 16 Nov 2023 08:47:56 -0500
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 by: Timothy Chow - Thu, 16 Nov 2023 13:47 UTC

XGID=-BACaBC-B-----c----bBbbcb-:0:0:1:52:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O X O O O O |
| O | | O X O O O O |
| O | | O |
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | X X |
| X | | X X X X |
| X | | X X O X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 97 O: 88 X-O: 0-0
Cube: 1
X to play 52

---
Tim Chow

Re: Time to break anchor? 2

<uj8192$2d4b1$2@dont-email.me>

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From: ah_c...@ymail.com (ah...Clem)
Newsgroups: rec.games.backgammon
Subject: Re: Time to break anchor? 2
Date: Fri, 17 Nov 2023 10:36:00 -0500
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 by: ah...Clem - Fri, 17 Nov 2023 15:36 UTC

On 11/16/2023 8:47 AM, Timothy Chow wrote:
> XGID=-BACaBC-B-----c----bBbbcb-:0:0:1:52:0:0:0:0:10
>
> Score is X:0 O:0. Unlimited Game
>  +13-14-15-16-17-18------19-20-21-22-23-24-+
>  |    O             |   | O  X  O  O  O  O |
>  |    O             |   | O  X  O  O  O  O |
>  |    O             |   |             O    |
>  |                  |   |                  |
>  |                  |   |                  |
>  |                  |BAR|                  |
>  |                  |   |                  |
>  |                  |   |                  |
>  |                  |   | X        X       |
>  |             X    |   | X  X     X     X |
>  |             X    |   | X  X  O  X  X  X |
>  +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count  X: 97  O: 88 X-O: 0-0
> Cube: 1
> X to play 52

Compared to the last problem in this series, X is now behind in the
race, there's no blot in O's homeboard to shoot at, but there are blots
for both in X's, and X can run a checker past O's outfield point.

Which is to say we can't apply the lessons of the last problem here.

I'll just clear the eight point again. This time, it covers the blot on
the deuce which seems to be a significant improvement in X's position.

Re: Time to break anchor? 2

<uj9bph$364nm$1@dont-email.me>

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Re: Time to break anchor? 2
Date: Fri, 17 Nov 2023 22:41:36 -0500
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 by: Timothy Chow - Sat, 18 Nov 2023 03:41 UTC

On 11/17/2023 10:36 AM, ah...Clem wrote:
> On 11/16/2023 8:47 AM, Timothy Chow wrote:
>> XGID=-BACaBC-B-----c----bBbbcb-:0:0:1:52:0:0:0:0:10
>>
>> Score is X:0 O:0. Unlimited Game
>>  +13-14-15-16-17-18------19-20-21-22-23-24-+
>>  |    O             |   | O  X  O  O  O  O |
>>  |    O             |   | O  X  O  O  O  O |
>>  |    O             |   |             O    |
>>  |                  |   |                  |
>>  |                  |   |                  |
>>  |                  |BAR|                  |
>>  |                  |   |                  |
>>  |                  |   |                  |
>>  |                  |   | X        X       |
>>  |             X    |   | X  X     X     X |
>>  |             X    |   | X  X  O  X  X  X |
>>  +12-11-10--9--8--7-------6--5--4--3--2--1-+
>> Pip count  X: 97  O: 88 X-O: 0-0
>> Cube: 1
>> X to play 52
>
>
>
> Compared to the last problem in this series, X is now behind in the
> race, there's no blot in O's homeboard to shoot at, but there are blots
> for both in X's, and X can run a checker past O's outfield point.
>
> Which is to say we can't apply the lessons of the last problem here.
>
> I'll just clear the eight point again. This time, it covers the blot on
> the deuce which seems to be a significant improvement in X's position.

Clearing the 8pt does not cover the blot on the deuce.

---
Tim Chow

Rollout: Time to break anchor? 2

<ujaj1d$3bjsp$1@dont-email.me>

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Rollout: Time to break anchor? 2
Date: Sat, 18 Nov 2023 09:51:23 -0500
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 by: Timothy Chow - Sat, 18 Nov 2023 14:51 UTC

XGID=-BACaBC-B-----c----bBbbcb-:0:0:1:52:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O X O O O O |
| O | | O X O O O O |
| O | | O |
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | X X |
| X | | X X X X |
| X | | X X O X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 97 O: 88 X-O: 0-0
Cube: 1
X to play 52

Playing 20/13 is a huge blunder in this position. O has no weaknesses
in her board while X has a blot, and X is behind in the race.

But there's another anchor-breaking play: 20/15 6/4*! This is the DMP
play but it would seem to lose far too many gammons to be a viable
candidate. Indeed, both XG 3-ply and XG 4-ply favor 6/1 3/1. Also,
if X owns the cube already then the rollout favors 6/1 3/1. So 20/15
6/4* is a "cube provocation play," which takes advantage of the highly
inefficient cube which the opponent must immediately send over. If
you think your opponent might not double from the bar, then 20/15 6/4*
becomes even more attractive.

Note that XG thinks that 8/6 8/3 is much worse than 6/1 3/1. Of course
it's usually bad to kill all those checkers on the 1pt, but 8/6 8/3 is
not going to win any beauty contests either. At minimum, it gives X
options for how to play a 6, and it also blocks some otherwise good
rolls for O (44 and 42 for example).

1. Rollout¹ 20/15 6/4* eq:-0.454
Player: 41.56% (G:7.47% B:0.06%)
Opponent: 58.44% (G:33.09% B:2.01%)
Confidence: ±0.014 (-0.469..-0.440) - [100.0%]

2. Rollout¹ 6/1 3/1 eq:-0.475 (-0.021)
Player: 35.99% (G:1.75% B:0.02%)
Opponent: 64.01% (G:4.85% B:0.13%)
Confidence: ±0.009 (-0.485..-0.466) - [0.0%]

3. Rollout¹ 8/6 8/3 eq:-0.577 (-0.123)
Player: 33.28% (G:2.19% B:0.04%)
Opponent: 66.72% (G:5.20% B:0.12%)
Confidence: ±0.008 (-0.585..-0.569) - [0.0%]

4. Rollout¹ 20/13 eq:-0.695 (-0.240)
Player: 33.76% (G:6.59% B:0.12%)
Opponent: 66.24% (G:17.63% B:0.34%)
Confidence: ±0.009 (-0.704..-0.686) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Rolled for both No double and Double
Dice Seed: 271828
First 3 moves: 3-ply, cube decisions: XG Roller+
Remaining moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

-------------
X owning cube
-------------

XGID=-BACaBC-B-----c----bBbbcb-:1:1:1:52:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O | | O X O O O O |
| O | | O X O O O O |
| O | | O |
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | X X | +---+
| X | | X X X X | | 2 |
| X | | X X O X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 97 O: 88 X-O: 0-0
Cube: 2, X own cube
X to play 52

1. Rollout¹ 6/1 3/1 eq:-0.186
Player: 35.92% (G:1.68% B:0.02%)
Opponent: 64.08% (G:4.80% B:0.12%)
Confidence: ±0.005 (-0.191..-0.180) - [100.0%]

2. Rollout¹ 20/15 6/4* eq:-0.229 (-0.043)
Player: 41.45% (G:7.51% B:0.07%)
Opponent: 58.55% (G:33.09% B:1.88%)
Confidence: ±0.007 (-0.236..-0.222) - [0.0%]

3. Rollout¹ 8/6 8/3 eq:-0.256 (-0.071)
Player: 33.19% (G:2.19% B:0.04%)
Opponent: 66.81% (G:5.11% B:0.12%)
Confidence: ±0.005 (-0.261..-0.251) - [0.0%]

4. Rollout¹ 20/13 eq:-0.350 (-0.164)
Player: 33.74% (G:5.99% B:0.11%)
Opponent: 66.26% (G:17.32% B:0.34%)
Confidence: ±0.005 (-0.354..-0.345) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

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