Midgame blitz cube action

[Timothy Chow]

XGID=a-BBB-BbB---baa-Ab-bbCbA--:1:1:1:00:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O X O | | O O X O X |
| O | | O O X O |
| | | X |
| | | |
| | | |
| |BAR| |
| | O | |
| | | |
| | | | +---+
| O X O | | X X X X | | 2 |
| O X O | | X X X X | +---+
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 148 O: 154 X-O: 0-0
Cube: 2, X own cube
X on roll, cube action

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Tim Chow

[Timothy Chow]

O has a checker on the bar against a four-point board, and X is
shooting at two more blots. This seemed like a clear redouble
to me. But XG begs to differ. It's a little hard for me to see
why XG thinks this redouble is such a big mistake. A hit and a
dance certainly loses X's market by a country mile, but I think
the trouble is that the less favorable exchanges are pretty bad.
There's certainly a 44 anti-joker, but even an "ordinary" miss,
followed by X getting hit back, would be very bad for X. Also,
if X hits and O enters one checker, it won't usually lose X's
market.

In the variant, I have shifted X's outfield blot by a pip, and
XG favors redoubling.

Analyzed in Rollout
No redouble
Player Winning Chances: 57.74% (G:37.42% B:2.26%)
Opponent Winning Chances: 42.26% (G:11.42% B:0.55%)
Redouble/Take
Player Winning Chances: 57.96% (G:37.61% B:2.46%)
Opponent Winning Chances: 42.04% (G:11.42% B:0.54%)

Cubeful Equities:
No redouble: +0.625
Redouble/Take: +0.535 (-0.090)
Redouble/Pass: +1.000 (+0.375)

Best Cube action: No redouble / Take
Percentage of wrong pass needed to make the double decision right: 19.4%

Rollout:
1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
Confidence No Double: ± 0.014 (+0.612..+0.639)
Confidence Double: ± 0.024 (+0.511..+0.560)

eXtreme Gammon Version: 2.19.211.pre-release

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Variant
-------

XGID=a-BBB-BbB---baaA-b-bbCbA--:0:0:1:00:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| O O X O | | O O X O X |
| O | | O O X O |
| | | X |
| | | |
| | | |
| |BAR| |
| | O | |
| | | |
| | | |

| O X O | | X X X X |
| O X O | | X X X X |

+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 147 O: 154 X-O: 0-0
Cube: 1

X on roll, cube action

Analyzed in Rollout
No double
Player Winning Chances: 60.21% (G:39.58% B:2.25%)
Opponent Winning Chances: 39.79% (G:10.80% B:0.57%)
Double/Take
Player Winning Chances: 60.44% (G:39.94% B:2.40%)
Opponent Winning Chances: 39.56% (G:10.91% B:0.59%)

Cubeful Equities:
No double: +0.638 (-0.060)
Double/Take: +0.699
Double/Pass: +1.000 (+0.301)

Best Cube action: Double / Take

Rollout:
1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
Confidence No Double: ± 0.016 (+0.623..+0.654)
Confidence Double: ± 0.023 (+0.676..+0.721)

eXtreme Gammon Version: 2.19.211.pre-release

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Tim Chow