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interests / rec.games.backgammon / Rollout: Run the back checker?

SubjectAuthor
* Run the back checker?Timothy Chow
+- Re: Run the back checker?Robert Zimmerman
+- Re: Run the back checker?Stick Rice
`- Rollout: Run the back checker?Timothy Chow

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Run the back checker?

<tt01e1$ppef$2@dont-email.me>

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Run the back checker?
Date: Mon, 20 Feb 2023 09:51:46 -0500
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 by: Timothy Chow - Mon, 20 Feb 2023 14:51 UTC

XGID=-a----E-D---dC-b--ceB---A-:0:0:1:62:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X X |
| X O O | | O X |
| X O | | O |
| | | O |
| | | O |
| |BAR| |
| | | X |
| O X | | X |
| O X | | X |
| O X | | X |
| O X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 165 O: 147 X-O: 0-0
Cube: 1
X to play 62

---
Tim Chow

Re: Run the back checker?

<6d060297-811f-46e9-a582-0edcd27b951bn@googlegroups.com>

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Subject: Re: Run the back checker?
From: zimbrook...@gmail.com (Robert Zimmerman)
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 by: Robert Zimmerman - Mon, 20 Feb 2023 15:30 UTC

On Monday, February 20, 2023 at 9:51:47 AM UTC-5, Timothy Chow wrote:
> XGID=-a----E-D---dC-b--ceB---A-:0:0:1:62:0:0:0:0:10
>
> Score is X:0 O:0. Unlimited Game
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X O O | | O X X |
> | X O O | | O X |
> | X O | | O |
> | | | O |
> | | | O |
> | |BAR| |
> | | | X |
> | O X | | X |
> | O X | | X |
> | O X | | X |
> | O X | | X O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 165 O: 147 X-O: 0-0
> Cube: 1
> X to play 62
>
> ---
> Tim Chow

The board is setting up as a holding game, but I would also try to attack O's back checker and try to get out of the holding game. A holding game with a goal keeper (I think that's what I've seen the back checker called before) can look better than without, and running will give that up, but I would think the goalkeeper more valuable if O were more stacked and poorly distributed. With the 10 point made, O is doing ok and may not run into problems coming in.

Committing to a holding game right now cedes the advantage to O. Here it's still early in the game, and there's room for maneuvering for X to build some advantage. Running with the back checker can provide some outfield coverage against O's attempt to run, and it can become a builder in an attacking/priming effort on that blot. And if we later roll some good doubles, we might even the race. If hit in the outfield, we can return to the holding game. Nothing will have been lost in the race since we were already behind by 18 pips.

24/16 for me.
Bob

Re: Run the back checker?

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Subject: Re: Run the back checker?
From: bananabo...@gmail.com (Stick Rice)
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 by: Stick Rice - Mon, 20 Feb 2023 22:03 UTC

On Monday, February 20, 2023 at 9:51:47 AM UTC-5, Timothy Chow wrote:
> XGID=-a----E-D---dC-b--ceB---A-:0:0:1:62:0:0:0:0:10
>
> Score is X:0 O:0. Unlimited Game
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X O O | | O X X |
> | X O O | | O X |
> | X O | | O |
> | | | O |
> | | | O |
> | |BAR| |
> | | | X |
> | O X | | X |
> | O X | | X |
> | O X | | X |
> | O X | | X O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 165 O: 147 X-O: 0-0
> Cube: 1
> X to play 62
>
> ---
> Tim Chow

Variant: opp's rear checker moved forward two pips.

Stick

Rollout: Run the back checker?

<tt5h6v$1igvf$1@dont-email.me>

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Rollout: Run the back checker?
Date: Wed, 22 Feb 2023 11:51:42 -0500
Organization: A noiseless patient Spider
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 by: Timothy Chow - Wed, 22 Feb 2023 16:51 UTC

XGID=-a----E-D---dC-b--ceB---A-:0:0:1:62:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X X |
| X O O | | O X |
| X O | | O |
| | | O |
| | | O |
| |BAR| |
| | | X |
| O X | | X |
| O X | | X |
| O X | | X |
| O X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 165 O: 147 X-O: 0-0
Cube: 1
X to play 62

My variant is different from Stick's suggestion. Part of the point
here is that the most plausible alternative to running 24/16 is the
slotting play 13/5, which isn't particularly attractive. It strips
the midpoint and doesn't do a particularly good job of containing
O's straggler.

1. Rollout¹ 24/16 eq:-0.292
Player: 41.55% (G:8.49% B:0.25%)
Opponent: 58.45% (G:8.81% B:0.35%)
Confidence: ±0.012 (-0.304..-0.279) - [100.0%]

2. Rollout¹ 13/5 eq:-0.394 (-0.102)
Player: 39.77% (G:9.74% B:0.26%)
Opponent: 60.23% (G:12.00% B:0.47%)
Confidence: ±0.014 (-0.408..-0.380) - [0.0%]

3. Rollout¹ 13/11 8/2 eq:-0.405 (-0.113)
Player: 39.69% (G:9.37% B:0.27%)
Opponent: 60.31% (G:13.70% B:0.66%)
Confidence: ±0.015 (-0.420..-0.390) - [0.0%]

4. Rollout¹ 24/22 8/2 eq:-0.429 (-0.138)
Player: 38.72% (G:8.03% B:0.23%)
Opponent: 61.28% (G:11.41% B:0.41%)
Confidence: ±0.013 (-0.442..-0.416) - [0.0%]

5. Rollout¹ 24/22 13/7 eq:-0.435 (-0.143)
Player: 38.69% (G:8.31% B:0.22%)
Opponent: 61.31% (G:11.56% B:0.39%)
Confidence: ±0.013 (-0.448..-0.422) - [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

-------
Variant
-------

XGID=-a----E-C---dD-b-c-eB---A-:0:0:1:62:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X X |
| X O O | | O X |
| X O | | O |
| X | | O |
| | | O |
| |BAR| |
| | | X |
| O | | X |
| O X | | X |
| O X | | X |
| O X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 170 O: 150 X-O: 0-0
Cube: 1
X to play 62

1. Rollout¹ 13/11 13/7 eq:-0.301
Player: 42.20% (G:10.70% B:0.32%)
Opponent: 57.80% (G:13.49% B:0.57%)
Confidence: ±0.008 (-0.308..-0.293) - [89.7%]

2. Rollout¹ 24/16 eq:-0.309 (-0.008)
Player: 41.22% (G:8.58% B:0.26%)
Opponent: 58.78% (G:9.63% B:0.37%)
Confidence: ±0.007 (-0.316..-0.302) - [5.3%]

3. Rollout¹ 13/5 eq:-0.309 (-0.009)
Player: 41.62% (G:10.56% B:0.31%)
Opponent: 58.38% (G:12.23% B:0.50%)
Confidence: ±0.008 (-0.317..-0.302) - [5.0%]

4. Rollout¹ 24/18 13/11 eq:-0.322 (-0.021)
Player: 41.13% (G:9.08% B:0.31%)
Opponent: 58.87% (G:11.08% B:0.44%)
Confidence: ±0.007 (-0.329..-0.315) - [0.0%]

5. Rollout¹ 13/7 6/4 eq:-0.339 (-0.038)
Player: 41.76% (G:10.28% B:0.33%)
Opponent: 58.25% (G:14.63% B:0.69%)
Confidence: ±0.008 (-0.347..-0.331) - [0.0%]

¹ 5184 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

---------------
Stick's variant
---------------

XGID=---a--E-D---dC-b--ceB---A-:0:0:1:62:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O | | O X X |
| X O O | | O X |
| X O | | O |
| | | O |
| | | O |
| |BAR| |
| | | X |
| O X | | X |
| O X | | X |
| O X | | X |
| O X | | X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 165 O: 145 X-O: 0-0
Cube: 1
X to play 62

1. Rollout¹ 24/16 eq:-0.386
Player: 39.01% (G:7.34% B:0.22%)
Opponent: 60.99% (G:8.50% B:0.31%)
Confidence: ±0.006 (-0.392..-0.380) - [90.7%]

2. Rollout¹ 13/11 8/2 eq:-0.393 (-0.007)
Player: 39.09% (G:9.50% B:0.22%)
Opponent: 60.91% (G:10.96% B:0.50%)
Confidence: ±0.008 (-0.401..-0.385) - [9.3%]

3. Rollout¹ 13/5 eq:-0.408 (-0.021)
Player: 39.08% (G:9.27% B:0.26%)
Opponent: 60.92% (G:11.51% B:0.47%)
Confidence: ±0.007 (-0.415..-0.400) - [0.0%]

¹ 5184 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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