On Sunday, December 12, 2021 at 2:17:07 PM UTC, Tim Chow wrote:
XGID=--a-CaEAa---cBa--bbb-B-AbA:0:0:1:63:0:0:0:0:10
X:Player 1 O:Player 2
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 X X O |
| X O O | | O X O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | X |
| | | X |
| O | | X X |
| O | | X X |
| O O X | | X O X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 165 O: 154 X-O: 0-0
Cube: 1
X to play 63
In this sort of position, it's usually more important to jump the
prime than to minimize shots, since getting primed can lead to a
collapse and near-certain death, whereas getting hit is survivable.
However, here, O has only a three-point prime, and bar/16 does leave
a whole lot of shots. If we were to duplicate O's 4's to hit, then
the rollout would indicate a much closer decision (see variant below).
1. Rollout¹ Bar/22 7/1 eq:-0.408
Player: 39.68% (G:11.34% B:0.32%)
Opponent: 60.32% (G:17.72% B:0.67%)
Confidence: ±0.015 (-0.423..-0.393) - [100.0%]
2. Rollout¹ Bar/16 eq:-0.525 (-0.117)
Player: 38.69% (G:11.02% B:0.57%)
Opponent: 61.31% (G:21.98% B:0.77%)
Confidence: ±0.018 (-0.543..-0.507) - [0.0%]
3. Rollout¹ Bar/22 13/7 eq:-0.543 (-0.135)
Player: 37.10% (G:10.67% B:0.60%)
Opponent: 62.90% (G:19.30% B:0.72%)
Confidence: ±0.017 (-0.560..-0.526) - [0.0%]
¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
eXtreme Gammon Version: 2.19.207.pre-release
-------
Variant
-------
XGID=---aCaEAa---cBa--bbb-B-AbA:0:0:1:63:0:0:0:0:10
X:Player 1 O:Player 2
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 X X O |
| X O O | | O X O |
| | | |
| | | |
| | X | |
| |BAR| |
| | | X |
| | | X |
| O | | X X |
| O | | X X |
| O O X | | X O X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 165 O: 153 X-O: 0-0
Cube: 1
X to play 63
1. Rollout¹ Bar/16 eq:-0.436
Player: 40.22% (G:11.97% B:0.54%)
Opponent: 59.78% (G:20.61% B:0.78%)
Confidence: ±0.017 (-0.453..-0.419) - [82.7%]
2. Rollout¹ Bar/22 7/1 eq:-0.446 (-0.011)
Player: 38.84% (G:11.42% B:0.31%)
Opponent: 61.16% (G:17.68% B:0.70%)
Confidence: ±0.014 (-0.461..-0.432) - [17.3%]
¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
eXtreme Gammon Version: 2.19.207.pre-release
---
Tim Chow
Thanks for this -- my play was 13/7 (the worst of your 3.)
I did consider 7/1 but it looked antipositional to put a checker out of play like that,
and I didn't think such extreme safety was warranted.
Paul
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