Problem of the Week #30: September 27


Cash game. Center cube. Black on move.




Black to play 2-2.

13/11/9 11/9 6/4

I want to keep the 20pt.

I think that this is an error. Why do you want to shuffle your inner board spares around like this? I'd take the spare from the midpoint, instead. Your play makes your position front-loaded. Another advantage to having the spare in the outfield instead of the 4 point is that 11/61 will make your very important 5 point without breaking any other points.

13/9(2). Block the potential 3 point anchor and put your spares in places where they can make the important points. Also, hanging back on the 20 point will probably give you a shot on the next roll or two because white's position is stripped.

Positionally, I'm unstacking the 6pt and not stripping the midpoint. Tactically, I can now point on his head with 4 numbers: 1, 3, 5, and 6.

I don't think you should be worrying about stripping the midpoint in this position. Usually, you do that so you can continue to attack checkers as they run into the outfield without having to give up the midpoint. At this point in the match, your midpoint isn't going to be doing very much more work for you. You've got a lot of points in that outfield, and if you happen to be shooting at some blot, you don't really care so much if you lose the midpoint because you're going to want to roll your checkers right into your prime, and so you'll release both checkers from the anchor at once.

I also don't think that unstacking the 6 point is that much of a priority right now. It doesn't add all that much in the way of flexibility (because you're driving your spares deeper into your home board). Your bigger goal is to complete your prime, and this move is antithetical to that.

This doesn't make sense.

If you take a moment to compare the two positions, you only gain a couple pointing rolls (31, 61), but a blitzing type play isn't even all that strong because he's got an anchor (edit: that can see daylight with his 6s), and your board isn't that strong.

Well, I downloaded eXtremeGammon and ran an analysis of this position. With the two caveats that 1) XG is new and so unknown, and 2) I don't know what I'm doing with setting up analysis parameters, XG gives

13/9 (2) seems completely standard. I guess the other choice is 20/16 (2) with the idea of breaking contact later, but that seems premature here with such a nice move available on the other side of the board. Same goes for any other combination of moves, they just can't compete with simply making the 9-point, which leaves Hero with a flexible and powerful position.

We're ahead by 10 pips before the roll, 18 after. Although it's a tiny lead, I would not tend to engage in a blot-hitting contest, even though we had the security of an advanced anchor. With 3 White checkers back, priming/containing seems like a good game plan (considering that the roll doesn't allow us to attack). Disengaging with 20/16 (2) seems premature. Slotting the bar point seems risky. Even partially disengaging with 20/18 (2) doesn't seem appealing because we have 2 other deuces to play.

I'd go with 13/9 (2), making a useful blocking point that can be part of a prime (at least temporarily) and also could be a good landing point in the future for outfield checkers as we prepare to bear-in against contact.

13/9, 11/9, 6/4 is an alternative. It has the merit of not stripping the midpoint, but I'm not sure about moving a builder from the 6-point to the 4-point. I'd still go with 13/9 (2).

+1 for 13/9 (2)

What Is White’s Game Plan?
You can learn a lot about this position by looking at it from White’s perspective. He is badly stripped everywhere, and must get his backmen moving on the next roll. Otherwise, White will face a tough decision choosing which of his outfield points to abandon.

White’s problem stems from the fact that Black has made a fine advanced anchor. White can neither prime Black, nor attack him. White might try escaping, but even that doesn’t seem promising. He has three men back (to Black’s two), and already trails in the race. Realistically, White’s best chance is to make an advanced anchor of his own. As is so often the case, once your opponent has made an advanced anchor, it is imperative that you step up to match him. Having secured his defense, White could then play using his third back checker, while hoping to outwait Black in a mutual holding game.

So much for White. What does all this mean for Black?

Hitting Won’t Work
It may take only half a second to reject the notion, but Black should be aware that he can hit loose on the three point with 11/3*. In view of his racing lead, however, and his decent structure, the risk of a loose hit is unwarranted. If White’s blot were sitting on the five point, of course, it would be a different story.

Running Won’t Work
After playing this 22, Black will lead in the race by 18 pips, so he should at least consider advancing his backmen, 20/16(2), in an attempt to disengage. In fact, if Black had already made his bar point and/or his five point, running might be his best play. Without them, however, it seems unlikely that Black can make it home safely. Therefore, he should keep his anchor, and use this roll to improve his front position.

So Make the Best Point…
What’s left? Black should use three of his twos to make his nine point, 13/9, 11/9. Making the eleven point, or pushing forward to make the two point, are both weaker alternatives. These weaker plays both spread Black’s forces across too wide a range. The nine point, on the other hand, primes White’s checker on the three point, and works well with the points Black has already made. Conceivably, Black might form a six-point prime extending from his four point to his nine point. In addition, the men on his nine point are semi-active builders, available to make a point on White’s head if he leaves a blot on the three, five or bar points.

… And Choose the Best Two
Finally, we reach the crux of this problem. How will Black play his fourth two? He can play safe with 6/4, or risk 3 shots by re-slotting his eleven point with 13/11. Black is ahead in the race, and should be reluctant to take any voluntary risks. But look how inflexible his position becomes after the safe play. Unless White is kind enough to provide a target for Black by moving up his blot, Black will find it very hard to make the all-important five or bar points without exposing himself to a direct shot in return.

Frankly, he doesn’t create very many more chances by bringing a builder down to the eleven point. His flexibility, however, is much improved. By stripping down to two men on the midpoint, Black will be ready to give up the point. Certain rolls (those without a one) that otherwise play awkwardly on the next turn, can be played by clearing the midpoint, providing additional builders for the key five and bar points.

My solution: 13/9(2)

For the Record
I have been answering these problems without the use of a bot, and before taking a peek at the excellent solutions of others, since Problem 28. My record at this writing is a meager 67% correct.
Correct: 28(a), 29
Incorrect: 28(b)

Correction: White will have 5 shots that hit on the eleven point.

Black's best play is still 13/9(2).