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BGonline.org Forums
Cube placement
Posted By: Rich Munitz In Response To: Cube placement (Tommy Nesbakk)
Date: Tuesday, 9 November 2010, at 9:31 p.m.
Making the 4 point with a centered cube makes this an effective last roll position as it gives you a pretty efficient double after a miss (with the possibility of winning on the 42 hit that leaves a direct), and you lose the rest of the time. So while you only win 56% of the time cubeless, you actually are winning 70% of the time due to cube efficiency. Note that in this case, while yellow is getting maximum cube value, black gets absolutely no value out of cube access, since after the hit his equity is about 1.0 whether he turns the cube or not. With the other two plays, black always retains the threat to use the cube later as the game drags on.
If you look at the alternatives, holding the prime will win more cubeless, but it is never likely to produce an efficient cube for you so in practice you'll never get up to the 70% level. Making the 3 point seems safer, but if you look at it, there are 8 immediate numbers off the roof that either get you hit or escape and an escape is effectively a loss if black has cube access. So you're really talking 8 losing numbers instead of 11. But the 12 times that black enters and doesn't win immediately, you are unable to cube efficiently, if at all. Since you'll probably lose 1/3 of those games, you're giving another 4 eventual losses on top of the immediate 8. And that's worse than giving the 11 immediates.
Now what changes when we move the cube from center? The simple case is when black owns the cube, as making the 4 point no longer results in an efficient double after a miss (because you can't cube). You get your 56% wins instead of your 70% wins. Clearly no bargain. When yellow owns the cube it is more interesting. Now you still have the efficient double making the 4 point after the miss. But whereas with the centered cube, black's racing edge threatens to give a nice double if he ever manages to escape after making the 3 point or holding the prime, here black cannot double and yellow will win more of these games by holding the cube.
In summary, with a centered cube, making the 4 point is best because it maximizes the value of yellow's cube access while minimizing the value of black's cube access. If the play cannot do both of those things simultaneously because the cube is moved from the center, it ceases to be best.
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