FIBS Board backgammon forum

Mentally moving the checkers in my head after Linus announced his move I thought it might be a cube, so I asked for a vote.  Now that I can actually see the position I think it's pretty clear that it's not a cube AtS.  But as long as we're here, lets do the analysis. 

First, what is his takepoint trailing 4a 2a?  If he passes, he's at 4a Crawford for 18% MWC.  If he takes and wins, re recubes and wins the match, so his takepoint is just the MWC if he passes, or 18%.  Does he have that here? Yes, I think so.

Second, what is our minimum doubling point (MDP)?  It's the same formula as the raw takepoint: risk/(risk + gain).  If we win without cubing, we are at 82%, while if we had cubed we're at 100%.  Our gain from doubling is then 18%.  If we lose witgh the cube in the center, we are at 3a 2a for 60% MWC, and if we have cubed we are at 0%, for a risk of 60%

risk/(risk + gain) = 60/78 or about 77%

So, our doubling window opens at 77% and closes at 82% - that's a small window, and we ain't in it.  Linus is only a few pips down in the race, so it wouldn't be double even if there were no contact and it was a "normal" score.  We have a few market losers, but not that many.  Gammons are few, but there are some and cubing kills them.

ND.

Cubing here would have been a massive blunder.

At an even match score, it's right on the cusp of being a double (see variant).  AtS, no way we're staking the match on this game.



XGID=-BBACaC-B---B-a---abcbbba-:0:0:1:00:3:1:0:5:3

X:Herd   O:Linus
Score is X:3 O:1 5 pt.(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
|    O           O |   | O  O  O  O  O  O |
|                  |   | O  O  O  O  O    |
|                  |   |    O             |
|                  |   |                  |
|                  |   |                  |
|                  |BAR|                  |
|                  |   |                  |
|                  |   |                  |
|                  |   | X     X          |
| X           X    |   | X     X     X  X |
| X           X    |   | X  O  X  X  X  X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count  X: 79  O: 84 X-O: 3-1/5
Cube: 1
X on roll, cube action

Analyzed in XG Roller++
Player Winning Chances:   68.34% (G:2.43% B:0.05%)
Opponent Winning Chances: 31.66% (G:2.71% B:0.04%)

Cubeless Equities: No Double=+0.383, Double=+1.192

Cubeful Equities:
       No double:     +0.481
       Double/Take:   -0.204 (-0.685)
       Double/Pass:   +1.000 (+0.519)

Best Cube action: No double / Take
Percentage of wrong pass needed to make the double decision right: 36.3%

eXtreme Gammon Version: 2.10, MET: Kazaross XG2


//////////////////variant/////////////////////////////

XGID=-BBACaC-B---B-a---abcbbba-:0:0:1:00:0:0:0:5:3

X:Player 1   O:Player 2
Score is X:0 O:0 5 pt.(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
|    O           O |   | O  O  O  O  O  O |
|                  |   | O  O  O  O  O    |
|                  |   |    O             |
|                  |   |                  |
|                  |   |                  |
|                  |BAR|                  |
|                  |   |                  |
|                  |   |                  |
|                  |   | X     X          |
| X           X    |   | X     X     X  X |
| X           X    |   | X  O  X  X  X  X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count  X: 79  O: 84 X-O: 0-0/5
Cube: 1
X on roll, cube action

Analyzed in XG Roller++
Player Winning Chances:   68.04% (G:2.51% B:0.06%)
Opponent Winning Chances: 31.96% (G:2.77% B:0.04%)

Cubeless Equities: No Double=+0.359, Double=+0.691

Cubeful Equities:
       No double:     +0.517 (-0.001)
       Double/Take:   +0.518
       Double/Pass:   +1.000 (+0.482)

Best Cube action: Double / Take

eXtreme Gammon Version: 2.10, MET: Kazaross XG2