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iBlunder

Posted By: Kevin Finch
Date: Thursday, 23 April 2015, at 1:55 a.m.

In Response To: iBlunder (Max Levenstein)

Two things make this a straightforward take: 1) you have significant racing equity, and 2) bottom player still has three men to extract from your board. The significance of the second point is highlighted in the following two positions.

In the first one note that the position is different in two ways compared to yours: top has no outfield coverage and two of the three bottom back men have escaped. (The race differential is the same as in your position.) Yet it is still a solid take:





White is Player 2

score: 0
pip: 89
Unlimited Game
Jacoby Beaver
pip: 133
score: 0

Blue is Player 1
XGID=--aB-BBBB-B------BbdcAcb--:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in XG Roller++ No double Double/Take
Player Winning Chances: 76.46% (G:5.41% B:0.15%) 76.80% (G:5.86% B:0.24%)
Opponent Winning Chances: 23.54% (G:6.72% B:0.13%) 23.20% (G:6.32% B:0.10%)
Cubeless Equities +0.516 +1.066
Cubeful Equities
No double:+0.823 (-0.114)
Double/Take:+0.937
Double/Pass:+1.000 (+0.063)
Best Cube action: Double / Take

eXtreme Gammon Version: 2.10

Now notice what happens if all three men have escaped (again the race difference is the same):





White is Player 2

score: 0
pip: 85
Unlimited Game
Jacoby Beaver
pip: 129
score: 0

Blue is Player 1
XGID=--aB-BBBB-B------Cbdb-cba-:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in XG Roller++ No double Double/Take
Player Winning Chances: 79.83% (G:4.55% B:0.09%) 80.32% (G:4.96% B:0.20%)
Opponent Winning Chances: 20.17% (G:4.53% B:0.05%) 19.68% (G:4.14% B:0.05%)
Cubeless Equities +0.597 +1.232
Cubeful Equities
No double:+0.921 (-0.079)
Double/Take:+1.130 (+0.130)
Double/Pass:+1.000
Best Cube action: Double / Pass

eXtreme Gammon Version: 2.10

It is surprising in looking at doubling decisions in these kinds of positions (from the taker's standpoint) how much of the equity is a function of his ability to contain one checker. Once that back checker is gone, it is game over, top's racing lead notwithstanding. In the first position above bottom player is a 3 to 1 favorite to escape that back man on the next roll, yet that 1 out of 4 chance is enough to merit the take.

Note that it is a tricky balance however: if, in the first position, top's spare on 20 were put on 24 (as in the second position) then it becomes a small pass. Turns out that in order to take you need to have three hitters (including the men on 18) to attack the lone man on 21 if he cannot escape. But this is getting into the weeds: the main point is that if you still have a some (or even one) of your oppt's men in your board, and you have a chance in the race, don't lose heart. Things may be better than you think.

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