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4pt vs 7pt 3

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: 4pt vs 7pt 3
Date: Wed, 14 Jun 2023 08:30:30 -0400
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by: Timothy Chow - Wed, 14 Jun 2023 12:30 UTC

XGID=-b-B-BD-C----Aa-cbbcbC----:1:-1:1:11:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X O O O O | | O O X | +---+
| O O O | | O O X | | 2 |
| O | | O X | +---+
| | | |
| | | |
| |BAR| |
| | | |
| | | X |
| X | | X |
| X | | X X X O |
| X | | X X X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 140 O: 144 X-O: 0-0
Cube: 2, O own cube
X to play 11

---
Tim Chow

Re: 4pt vs 7pt 3

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From: ah_c...@ymail.com (ah....Clem)
Newsgroups: rec.games.backgammon
Subject: Re: 4pt vs 7pt 3
Date: Wed, 14 Jun 2023 08:50:07 -0400
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by: ah....Clem - Wed, 14 Jun 2023 12:50 UTC

On 6/14/2023 8:30 AM, Timothy Chow wrote:
> XGID=-b-B-BD-C----Aa-cbbcbC----:1:-1:1:11:0:0:0:0:10
>
> Score is X:0 O:0. Unlimited Game
> +13-14-15-16-17-18------19-20-21-22-23-24-+
> | X O     O O O |   | O O X          | +---+
> |          O O O |   | O O X          | | 2 |
> |          O       |   | O     X          | +---+
> |                  |   |                  |
> |                  |   |                  |
> |                  |BAR|                  |
> |                  |   |                  |
> |                  |   | X                |
> |             X    |   | X                |
> |             X    |   | X X     X     O |
> |             X    |   | X X     X     O |
> +12-11-10--9--8--7-------6--5--4--3--2--1-+
> Pip count X: 140 O: 144 X-O: 0-0
> Cube: 2, O own cube
> X to play 11

Tim's observation that making the four point is usually better when
there are blots to be picked up seems to apply here, or rather it might
in reverse.

Initially, it seems like blocking sixes would be stronger than filling
in the four point. OTOH, making the four gives a solid four prime and
makes a fifth point. An observation of my own is that it's usually
better to make an additional point than shifting one already made.

So, I'll make the four point here.

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

Rollout: 4pt vs 7pt 3

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From: tchow12...@yahoo.com (Timothy Chow)
Newsgroups: rec.games.backgammon
Subject: Rollout: 4pt vs 7pt 3
Date: Fri, 16 Jun 2023 08:15:04 -0400
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by: Timothy Chow - Fri, 16 Jun 2023 12:15 UTC

XGID=-b-B-BD-C----Aa-cbbcbC----:1:-1:1:11:0:0:0:0:10

I said that playing 6/4(2) with snake eyes is usually better than making
the bar point, if the 5pt is made and O has blots. XG says that this
position is an exception. What gives?

Well, first of all, the rollout below says that 6/4(2) is only a 0.05
error, which is not huge IMO. But the main point is that this position
is absolutely a priming battle, and 8/7(3) 6/5 is a superior priming
play. We really don't want O to be able to escape a back checker with
a 6, and 8/7(3) 6/5 also gives us good chances of making the 4pt.

See also the variant, which is still a priming battle, but slightly
less so since O has only a four-prime and not a five-prime. There,
6/4(2) edges out making the bar point according to the rollout.

1. Rollout¹ 8/7(3) 6/5 eq:-0.036
Player: 54.08% (G:15.93% B:0.53%)
Opponent: 45.92% (G:8.91% B:0.31%)
Confidence: ±0.009 (-0.045..-0.026) - [100.0%]

2. Rollout¹ 6/4(2) eq:-0.086 (-0.050)
Player: 51.64% (G:16.71% B:0.50%)
Opponent: 48.36% (G:8.60% B:0.29%)
Confidence: ±0.010 (-0.096..-0.076) - [0.0%]

3. Rollout¹ 13/12 8/7(2) 6/5 eq:-0.090 (-0.054)
Player: 52.59% (G:15.43% B:0.56%)
Opponent: 47.41% (G:9.90% B:0.30%)
Confidence: ±0.011 (-0.101..-0.079) - [0.0%]

4. Rollout¹ 13/12 8/7(3) eq:-0.098 (-0.062)
Player: 52.08% (G:14.87% B:0.49%)
Opponent: 47.92% (G:9.20% B:0.31%)
Confidence: ±0.010 (-0.108..-0.089) - [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=-b-B-BD-C----Aab-bccbC----:1:-1:1:11:0:0:0:0:10

1. Rollout¹ 6/4(2) eq:+0.045
Player: 55.91% (G:18.77% B:0.62%)
Opponent: 44.09% (G:8.32% B:0.31%)
Confidence: ±0.010 (+0.035..+0.055) - [100.0%]

2. Rollout¹ 13/12 8/7(2) 6/5 eq:+0.012 (-0.033)
Player: 55.62% (G:17.72% B:0.70%)
Opponent: 44.38% (G:9.71% B:0.39%)
Confidence: ±0.010 (+0.002..+0.023) - [0.0%]

3. Rollout¹ 8/7(3) 6/5 eq:+0.003 (-0.042)
Player: 54.92% (G:17.31% B:0.69%)
Opponent: 45.08% (G:8.87% B:0.34%)
Confidence: ±0.011 (-0.008..+0.014) - [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

A man is known by the company he organizes. -- Ambrose Bierce

interests / rec.games.backgammon / 4pt vs 7pt 3

Subject	Author
4pt vs 7pt 3	Timothy Chow
Re: 4pt vs 7pt 3	ah....Clem
Rollout: 4pt vs 7pt 3	Timothy Chow