On Wednesday, October 27, 2021 at 4:05:27 AM UTC+1, Tim Chow wrote:
XGID=--a-CBCB----bB---d-cbcB--A:0:0:1:43:0:0:0:0:10
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 | | O O O X |
| O | | O O |
| O | | |
| | X | |
| |BAR| |
| | | |
| | | |
| | | X X |
| O 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: 149 O: 121 X-O: 0-0
Cube: 1
X to play 43
I think of this as a containment position. O can jump out with a 6
but she is not at the edge of X's prime, so hitting is not particularly attractive. Jumping out might seem risky, but O's sixes are duplicated
to jump out and hit, and her midpoint is stripped. Putting a checker
on the 18pt improves X's outfield coverage in case O does jump out.
The two variants below show how the relative merits of bar/18 and 6/2* change when we move some spares around.
1. Rollout¹ Bar/18 eq:-0.244
Player: 43.42% (G:9.85% B:0.38%)
Opponent: 56.58% (G:13.14% B:0.46%)
Confidence: ±0.012 (-0.255..-0.232) - [100.0%]
2. Rollout¹ Bar/22 6/2* eq:-0.350 (-0.107)
Player: 42.09% (G:9.48% B:0.31%)
Opponent: 57.91% (G:17.70% B:0.62%)
Confidence: ±0.014 (-0.364..-0.337) - [0.0%]
3. Rollout¹ Bar/22 13/9 eq:-0.446 (-0.202)
Player: 38.29% (G:8.13% B:0.31%)
Opponent: 61.71% (G:15.79% B:0.56%)
Confidence: ±0.012 (-0.457..-0.434) - [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 1
---------
XGID=--a-BBDB----bB---d-cbcB--A:0:0:1:43:0:0:0:0:10
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 | | O O O X |
| O | | O O |
| O | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| | | X |
| O 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: 151 O: 121 X-O: 0-0
Cube: 1
X to play 43
1. Rollout¹ Bar/18 eq:-0.272
Player: 42.79% (G:9.49% B:0.36%)
Opponent: 57.21% (G:13.41% B:0.44%)
Confidence: ±0.012 (-0.284..-0.260) - [99.9%]
2. Rollout¹ Bar/22 6/2* eq:-0.302 (-0.029)
Player: 43.25% (G:9.69% B:0.32%)
Opponent: 56.75% (G:17.01% B:0.64%)
Confidence: ±0.014 (-0.315..-0.288) - [0.1%]
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 2
---------
XGID=--a-BBDB----cB---c-cbcB--A:0:0:1:43:0:0:0:0:10
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 | | O O O X |
| O | | O O |
| | | |
| | X | |
| |BAR| |
| | | |
| | | X |
| O | | X |
| O 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: 151 O: 126 X-O: 0-0
Cube: 1
X to play 43
1. Rollout¹ Bar/22 6/2* eq:-0.332
Player: 41.94% (G:10.11% B:0.29%)
Opponent: 58.06% (G:16.07% B:0.64%)
Confidence: ±0.012 (-0.345..-0.320) - [80.2%]
2. Rollout¹ Bar/18 eq:-0.340 (-0.008)
Player: 41.33% (G:9.31% B:0.31%)
Opponent: 58.67% (G:13.20% B:0.54%)
Confidence: ±0.012 (-0.352..-0.327) - [19.8%]
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
I'm pretty sure I would have answered this correctly though, without actually Walting,
it's hard to be sure.
One surprise to me from XG's play is how often XG recommends going to the opponent's 18 point, subjecting
oneself to a barrage of shots. It certainly made me more willing to consider such plays OTB and having a stack of 3
on the 22 point looks ugly.
Paul
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