Backgammon book needed

[[e-mail]]

My double below was somewhat confident although wrong.
Of course I knew it was a take.

I'm not surprised by my equity of 0.5. But with 2's being devastating
and the opponent trapped between my 5 prime, why is doubling so bad?

Could someone write a book to explain why?

Thank You.

Paul

XGID=----cCCBCB--aA-----bcbca-A:1:1:1:00:0:0:0:11:10

X:Daniel O:XG Roller+
Score is X:0 O:0 11 pt.(s) match.
[phone]------19-20-21-22-23-24-+
| X | | O O O O O |
| | | O O O O |
| | | O O |
| | | |
| | X | |
| |BAR| |
| | | |
| | | |
| X | | X X O | +---+
| X X X | | X X O | | 2 |
| O X X X | | X X O | +---+
[phone]-------6--5--4--3--2--1-+
Pip count X: 127 O: 122 X-O: 0-0/11
Cube: 2, X own cube
X on roll, cube action

Analyzed in XG Roller+
Player Winning Chances: 63.55% (G:12.54% B:0.38%)
Opponent Winning Chances: 36.45% (G:11.35% B:0.16%)

Cubeless Equities: No Double=+0.286, Double=+0.590

Cubeful Equities:
No redouble: +0.516
Redouble/Take: +0.382 (-0.134)
Redouble/Pass: +1.000 (+0.484)

Best Cube action: No redouble / Take
Percentage of wrong pass needed to make the double decision right: 17.8%

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

[Timothy Chow]

Post by ***@gmail.com
My double below was somewhat confident although wrong.
Of course I knew it was a take.
I'm not surprised by my equity of 0.5. But with 2's being devastating
and the opponent trapped between my 5 prime, why is doubling so bad?

I think it's because your opponent's advanced anchor is more
powerful than you might think. Even if you hit, your opponent
could win by counterpriming or counterattacking, as long as
she doesn't collapse. The race is also close, which will be
important if O can spring a back checker. For example, suppose
you roll 61 from the bar (played bar/18) and your opponent rolls
61. All of a sudden you're the underdog.

Shift all the checkers on the near side of the board by one pip
and the story changes:

XGID=---cCCBCB---aA-----bcbca-A:1:1:1:00:0:0:0:11:10

Score is X:0 O:0 11 pt.(s) match.
[phone]------19-20-21-22-23-24-+
| X | | O O O O O |
| | | O O O O |
| | | O O |
| | | |
| | X | |
| |BAR| |
| | | |
| | | |
| X | | X X O | +---+
| X X | | X X X O | | 2 |
| O X X | | X X X O | +---+
[phone]-------6--5--4--3--2--1-+
Pip count X: 114 O: 125 X-O: 0-0/11
Cube: 2, X own cube
X on roll, cube action

Analyzed in Rollout
No redouble
Player Winning Chances: 66.09% (G:19.08% B:0.60%)
Opponent Winning Chances: 33.91% (G:9.97% B:0.21%)
Redouble/Take
Player Winning Chances: 66.12% (G:19.11% B:0.60%)
Opponent Winning Chances: 33.88% (G:9.79% B:0.46%)

Cubeful Equities:
No redouble: +0.656 (-0.003)
Redouble/Take: +0.659
Redouble/Pass: +1.000 (+0.341)

Best Cube action: Redouble / Take

Rollout:
1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
Confidence No Double: ± 0.008 (+0.648..+0.665)
Confidence Double: ± 0.014 (+0.645..+0.673)

eXtreme Gammon Version: 2.19.211.pre-release, MET: Kazaross XG2

---
Tim Chow