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interests / rec.games.backgammon / If you didn't have to play the 6 at all, would you? 2

SubjectAuthor
* If you didn't have to play the 6 at all, would you? 2Timothy Chow
`* Rollout: If you didn't have to play the 6 at all, would you? 2Timothy Chow
 `- Re: Rollout: If you didn't have to play the 6 at all, would you? 2Philippe Michel

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If you didn't have to play the 6 at all, would you? 2

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Path: i2pn2.org!i2pn.org!eternal-september.org!reader01.eternal-september.org!.POSTED!not-for-mail
From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: If you didn't have to play the 6 at all, would you? 2
Date: Mon, 21 Nov 2022 09:34:06 -0500
Organization: A noiseless patient Spider
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 by: Timothy Chow - Mon, 21 Nov 2022 14:34 UTC

XGID=-a-aB-E-B--AdC---c-e-a--AA:0:0:1:61:0:0:0:0:10

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 O | | O |
| X O | | O |
| | | O |
| | X | O |
| |BAR| |
| | | X |
| O | | X |
| O | | X |
| O X | | X X |
| O X X | | X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 153 O: 156 X-O: 0-0
Cube: 1
X to play 61

---
Tim Chow

Rollout: If you didn't have to play the 6 at all, would you? 2

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Rollout: If you didn't have to play the 6 at all, would you? 2
Date: Wed, 23 Nov 2022 10:28:49 -0500
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 by: Timothy Chow - Wed, 23 Nov 2022 15:28 UTC

XGID=-a-aB-E-B--AdC---c-e-a--AA:0:0:1:61:0:0:0:0:10

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 O | | O |
| X O | | O |
| | | O |
| | X | O |
| |BAR| |
| | | X |
| O | | X |
| O | | X |
| O X | | X X |
| O X X | | X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 153 O: 156 X-O: 0-0
Cube: 1
X to play 61

Here I'm pretty sure that it would be better not to play the 6 at all.
But since we have to play it, there are four legal 6's. Obviously we
can exclude 8/2 immediately, and 13/7 is not going to be better than
11/5---11/5 duplicates the opponent's 2's and 4's to hit and cover,
slots the better point, and avoids stripping the midpoint. The choice
is really between bar/18 and bar/24 11/5. Often in the early game,
stepping out to the opponent's bar point is the right idea when you're
slightly ahead in the race, but here, duplication suggests that 11/5
should be better. See the variant for comparison.

1. Rollout¹ Bar/24 11/5 eq:+0.171
Player: 52.97% (G:19.84% B:1.00%)
Opponent: 47.03% (G:13.24% B:0.83%)
Confidence: ±0.015 (+0.156..+0.186) - [100.0%]

2. Rollout¹ Bar/18 eq:+0.090 (-0.082)
Player: 52.44% (G:16.66% B:0.90%)
Opponent: 47.56% (G:15.40% B:0.77%)
Confidence: ±0.013 (+0.076..+0.103) - [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-aB-E-B--AdC---c-ea---AA:0:0:1:61:0:0:0:0:10

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 O | | O |
| X O | | O |
| | | O |
| | X | O |
| |BAR| |
| | | X |
| O | | X |
| O | | X |
| O X | | X X |
| O X X | | X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 153 O: 157 X-O: 0-0
Cube: 1
X to play 61

1. XG Roller++ Bar/18 eq:+0.030
Player: 51.13% (G:14.52% B:0.74%)
Opponent: 48.87% (G:15.03% B:0.65%)

2. XG Roller++ Bar/24 11/5 eq:-0.012 (-0.042)
Player: 48.99% (G:16.50% B:0.67%)
Opponent: 51.01% (G:14.48% B:0.83%)

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

Re: Rollout: If you didn't have to play the 6 at all, would you? 2

<tlollu$nont$1@dont-email.me>

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From: philippe...@free.fr.invalid (Philippe Michel)
Newsgroups: rec.games.backgammon
Subject: Re: Rollout: If you didn't have to play the 6 at all, would you? 2
Date: Thu, 24 Nov 2022 20:54:22 -0000 (UTC)
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 by: Philippe Michel - Thu, 24 Nov 2022 20:54 UTC

On 2022-11-23, Timothy Chow <tchow12000@yahoo.com> wrote:

> XGID=-a-aB-E-B--AdC---c-e-a--AA:0:0:1:61:0:0:0:0:10
>
> 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 O | | O |
> | X O | | O |
> | | | O |
> | | X | O |
> | |BAR| |
> | | | X |
> | O | | X |
> | O | | X |
> | O X | | X X |
> | O X X | | X X O O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 153 O: 156 X-O: 0-0
> Cube: 1
> X to play 61
>
> Here I'm pretty sure that it would be better not to play the 6 at all.

In fact it wouldn't.

GNUbg's evaluations of the position:

1. Cubeful 4-ply bar/24 11/5 Eq.: +0.160
0.529 0.192 0.010 - 0.471 0.132 0.008
4-ply cubeful prune [4ply]
2. Cubeful 4-ply bar/18 Eq.: +0.088 (-0.073)
0.526 0.163 0.009 - 0.474 0.150 0.007
4-ply cubeful prune [4ply]

Very close to XG's rollout, evaluations of this kind of early game
positions seem accurate.

Looking at a 2-1 from the obvious variant that would give the same
result as not playing the 6 in the original position:

1. Cubeful 4-ply bar/24 13/11 Eq.: +0.067
0.512 0.176 0.008 - 0.488 0.145 0.009
4-ply cubeful prune [4ply]

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