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6-away 9-away re-cube calculation

Posted By: Daniel Murphy
Date: Wednesday, 12 June 2013, at 9:35 p.m.

In Response To: 6-away 9-away re-cube calculation (Marv Porten)

(1) Is it possible to calculate this re-cube action over-the-board in a reasonable amount of time?

I think you could calculate this over the board in a reasonable time if you knew (1) your match equity table, and (2) that if you take, this position ...

The score (after 0 games) is: White 0, Blue 3 (match to 9 points)

Move number 7: White on roll, cube decision?

White5

Blue3
Position ID: BwAA8AEAAAAAAA Match ID: AgEgAQAAGAAE

... will occur 5/6 of the time and is a redouble to 8 with you winning about 25% of the time (the other 1/6 of the time you lose 4 points).

So in the original position,

 (1) if you pass, you trail 9-away 4-away for 21% MWC (2) if you take, there are only two outcomes to calculate (a) you trail 9-away 2-away for 10% MWC about 16% of the time (and 10% of 16% is 1.6%) (b) you lead 1-away 6-away Crawford for about 89% MWC about 21% of the time (because 1/4 of 5/6 = 5/24 = 20.8%) (and 89% of 21% is 18.7%)

Since 1.6% + 18.7% = 20.3%, less than 21%, White should pass in the original position.

(2) For Blue to properly calculate whether to re-double, must he determine his MWC if White takes AND re-cubes to 8 (if Blue does not roll an initial doublet), and compare that MWC to his MWC if White drops?

No, not here. Blue doesn't have to calculate his no-double equity, since he can first ask whether White should take, and since White should pass, the double is automatic, assuming equal players.

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