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Posted By: John O'Hagan
Date: Tuesday, 17 September 2013, at 3:00 a.m.

In Response To: Cube action ATS? (John O'Hagan)

This came up in a match I played recently vs. XGR+. The trailer clearly has a take ATS since I miss with 12 numbers. Given that, should the leader double? This is almost a last roll position which means redoubling is worth a close look.

Let's figure out the leader's minimum redoubling point. If our winning chances are below this, redoubling can't be correct. If we redouble, I assume it will go R/P after any of the twelve misses and that my side wins 23 of the 24 games where we hit. The reality is slightly worse than this for our side since the trailer is slightly TG if we dance or miss with 41.

Don't redouble and lose: Ahead 4-2 with 65% MWC. Do redouble and lose : Tied 4-4 with 50% MWC after 12 of the losses and lose the match with 0% after the one loss where we hit but go on to lose the game.

So we lose 15% MWC in twelve of our losses and 65% in the other. That's 245/13 which close to 19%.

Now for the gain.

Don't redouble and win : Ahead 6-0 Crawford with 91% MWC. Do redouble and win : Win match with 100% MWC.

So the gain is 9%.

The minimum redoubling point is 19/28 which is close to 68%. We only win 23/36 which is about 64%. So no redouble.

is Player 2

score: 0
pip: 27
7 point match
pip: 80
score: 4

is Player 1
XGID=-BBBCBB--A---------a--affA:1:1:1:00:4:0:0:7:10
on roll, cube action?

Analyzed in Rollout No redouble Redouble/Take
Player Winning Chances: 64.24% (G:0.00% B:0.00%) 64.18% (G:0.00% B:0.00%)
Opponent Winning Chances: 35.76% (G:0.20% B:0.00%) 35.82% (G:0.20% B:0.00%)
Cubeless Equities +0.282 +0.326
Cubeful Equities
No redouble:+0.3370.000 (+0.336..+0.337)
Redouble/Take:+0.210 (-0.127)0.002 (+0.208..+0.212)
Redouble/Pass:+1.000 (+0.663)
Best Cube action: No redouble / Take
Percentage of wrong pass needed to make the double decision right: 13.8%
Rollout details
1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 8.3 seconds

eXtreme Gammon Version: 2.00, MET: Kazaross XG2

23/36 winning chances would be enough to redouble IF this was a last roll position, as you can see below.

is Player 2

score: 0
pip: 2
7 point match
pip: 6
score: 4

is Player 1
XGID=--A-A-------------------b-:1:1:1:00:4:0:0:7:10
on roll, cube action?

Analyzed in XG Roller+ No redouble Redouble/Take
Player Winning Chances: 63.89% (G:0.00% B:0.00%) 63.89% (G:0.00% B:0.00%)
Opponent Winning Chances: 36.11% (G:0.00% B:0.00%) 36.11% (G:0.00% B:0.00%)
Cubeless Equities +0.278 +0.323
Cubeful Equities
No redouble:+0.278 (-0.045)
Redouble/Take:+0.323
Redouble/Pass:+1.000 (+0.677)
Best Cube action: Redouble / Take

eXtreme Gammon Version: 2.00, MET: Kazaross XG2

Here redoubling risks 15 to gain 9 so the minimum redoubling point is 15/24 which is 62.5%. Your chances are greater than this and it's the last roll of the game so R/T would be correct.

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