Double from the bar?

Discussion:

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Tim Chow

2017-04-20 23:41:39 UTC

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BlueDice

2017-04-21 14:14:36 UTC

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Post by Tim Chow
XGID=--B-BBCa----cBaa-d-d--AaBA:0:0:1:00:0:0:0:0:10
X:Player 2 O:Player 1
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 O X |
| X O | | O X |
| O | | O |
| O | | O |
| | X | |
| |BAR| |
| | | |
| | | |
| O | | X |
| O | | X X X X |
| O O | | X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 161 O: 136 X-O: 0-0
Cube: 1
X on roll, cube action
---
Tim Chow

D/P
X has 29 shots this roll, a 4 point board against a 1 point board. O has 4 blots lying around. Despite having 4 checkers back, I think X wins too many gammons to make it a take.
--
BD

BlueDice

2017-04-21 14:24:21 UTC

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D/P
X hits with 2s, 1s and 6s except 61 or 66 = 24 shots + 55 + 33 = 26 shots.
X has an overwhelming board advantage.
O has 4 blots lying around.
I think O loses too many gammons to make it a take.
--
BD

Walt

2017-04-21 14:34:07 UTC

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I count twenty-six hitting rolls and then sixteen dancing numbers.
That's gives the nine stipulated by O'Hagen's law, and some of the
entering rolls might still be a cash. Plus there's three shakes that hit
two checkers.

The other part of O'Hagen's law is that nothing particularly bad should
happen if we miss the market losers and that seems to be true. Dancing
with a 66 will be bad, but most everything else either hits or makes an
advanced anchor.

The take seems clear due to the race lead.

D/T

--
//Walt

Paul

2017-04-29 07:24:09 UTC

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Post by Walt

I count twenty-six hitting rolls and then sixteen dancing numbers.
That's gives the nine stipulated by O'Hagen's law, and some of the
entering rolls might still be a cash. Plus there's three shakes that hit
two checkers.
The other part of O'Hagen's law is that nothing particularly bad should
happen if we miss the market losers and that seems to be true. Dancing
with a 66 will be bad, but most everything else either hits or makes an
advanced anchor.
The take seems clear due to the race lead.
D/T

Although we now know this is wrong, this actually accords
with what I was thinking before I saw the rollout.
A double because of the threats and a take because of
the racing lead.

Good problem.

Paul

Michael

2017-04-21 16:27:39 UTC

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I didn't know where to start from although Doubling up looks very tempting for Otb conditions. Anyway I thought of first estimating the gammon rate for X. I 've estimated it to the 60-70% range. Keeping O's gammon rates to normal (20%) I used my "Doubling points.png" from here and found that X can double at something between 56 and 58%.
Therefore this is a sure Double X must have more than that, something about 65 +/-5%

The big question is what is the actual winning chance for X??
At these gammon rates (according to my program) the Cash point is ~ 64%.
Does he have that much winning chances? Does he not?
I don't have the ability to estimate anything at better accuracy than +/-5% and even if my b.m. estimates were right I wouldn't be able to proceed.

D/??

Michael

2017-04-21 16:29:47 UTC

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from here--> from here : https://drive.google.com/drive/folders/0B7L6em2ChhMOZmpxYmtrTE5aUlU

Tim Chow

2017-04-22 16:24:41 UTC

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XGID=--B-BBCa----cBaa-d-d--AaBA:0:0:1:00:0:0:0:0:10

X:Player 2 O:Player 1
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 O X |
| X O | | O X |
| O | | O |
| O | | O |
| | X | |
| |BAR| |
| | | |
| | | |
| O | | X |
| O | | X X X X |
| O O | | X X X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 161 O: 136 X-O: 0-0
Cube: 1
X on roll, cube action

According to the rollout, this is a huge pass. I underestimated X's
gammon chances here; 1's, 2's, and 6's hit, and O has four blots scattered
around the board with no structure. Even though X is on the bar and is 25
pips behind, the computer estimates that X wins about 40% gammons cubeless.

Analyzed in Rollout
No double
Player Winning Chances: 67.13% (G:42.33% B:4.57%)
Opponent Winning Chances: 32.87% (G:7.34% B:0.40%)
Double/Take
Player Winning Chances: 67.25% (G:43.30% B:4.65%)
Opponent Winning Chances: 32.75% (G:7.65% B:0.47%)

Cubeful Equities:
No double: +0.863 (-0.137)
Double/Take: +1.221 (+0.221)
Double/Pass: +1.000

Best Cube action: Double / Pass

Rollout:
1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller
Confidence No Double: ± 0.015 (+0.848..+0.877)
Confidence Double: ± 0.021 (+1.201..+1.242)

eXtreme Gammon Version: 2.19.208.pre-release

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Tim Chow