the dorbel daily

Thursday, 13 October 2011

The Famous Five

A little Quiz for you today, five puzzling positions from a student in Croatia. All of these are from money play, where as always the Jacoby Rule is in force and there are no scores to alter the value of gammons and the cube, so they should be easy, right? Let's see, in each position Black is on roll.

Position 1

Black to play 4-2. What and why?

Position 2

Black's 5-5 attack in the opening has failed miserably and now he has to play 6-5 from the bar. A choice of three sixes, so which and why?

Position 3

Black has already doubled and now has a nice 2-1 to play. This one will surprise a lot of you I know. What and why?

Position 4

Black to play a 3-1, neither easy nor obvious. What and why please.

Position 5

It has been said that the ability to play a poor roll well is "the calling card of a pro". This is a poor roll, so can you find Black's best play here? What and why please!

If you get all these right for the right reasons, then you should be writing your own blog. I'll be back in a day or two, with some of the thinking which might lead you to the right play if you meet these toughies one dark night.
Until then, enjoy the game!


ah_clem said...

The instructions don't say whether the Jacoby rule is in force. I'll assume it is.

1) White has escaped all her checkers while black has three men back. But Black has a much better board. All the Magriel criteria point to bold play.

Making the four point now seems obvious. It's clearly the next point to make, and we have the chance to make it now, so we should. Then, after making it the next objective will be to make the three point. 6/4 13/9 aims two builders at the three, so this is a real contender.

What about those back checkers? Do we want to try to make a "better" anchor by slotting the 21 or even the 20? I say no - we're behind in the race, so let's stay back so that White can't just dump checkers behind our runners.

22/16 is intriguing, and is certainly bold, but it seems a bit too bold. I'll stick with making the four and prepping to make the three.

6/4 13/9

2)White has no board. Slot the opponent's 5 and bar points and we'll probably make one of them next roll. THis entices white to hit loose on one of them and provoking an exchange of hits is exactly what we want to do with our better board.

The other choices are a) slotting our own bar point, but with White already half escaped the bar point is not nearly as valuable as usual, and b) running out to the 14, but this leaves us squatting on the ace point while giving White the opportunity to break all other contact. I hate playing ace-point games, so running is out for me.

bar/20 24/18

3) The choice is between hitting and making the 7 point. While the 5-prime is strong, the additional gammons obtained by hitting seem to point towards hitting. So I'll hit here.

The obvious hit is 14/12*/11, but the better play appears to be 14/12* 23/22. Those blots on the11 and 12 are not in any immediate danger (no rolls hit from the bar) and by leaving them split we gain more numbers to make the bar point. Also, by moving up to the 22 we got 4s and 6s to leap instead of just 5s.

14/12* 23/22

4) If I counted right, Black trails in the race 114 to 98. If black plays safely, white will have a 12 pip lead which is right on the edge of Blacks takepoint (10%+2 is the point of last take).

So, playing safe basically hands White a super efficient cube to bash Black over the head with. The bold play (14/13*/10) gives White a chance to dance while black has three builders ready to cover the blot on the four. I don't think White has a double from the bar, so the next time White has a chance to cube either black will probably have covered the blot and it's no cube, or black will be sitting on the bar against a formidable board and it cash time for white.

With Jacoby, there's no gammon threat (yet) so Black can afford the bold play.


5)Black is slightly behind in the race and has the better board. A bold play is called for. Stripping the 8 and 6 points to make the two is too timid here. So is abandoning the 10 and stacking the six.

I'll play 22/16 13/9. Not sure if it's right, but it should provoke an exchange of hits which works to blacks advantage.

dorbel said...

Thanks Clem. All money play is played with the jacoby Rule, but I have added it to the instructions.

boop said...

taken from Boop's 501 bad moves in backgammon

1) 22/16. A prime is looming. Hopefully this forces contact while I posess a far superior homeboard. if white fails to hit, a 6 or 7 (21 numbers) halts the prime and secures the landing point for the final back checker.

2) bar 20, 24/18. only 61, 31,33,66 are bad returns. any other loose hits from white gives black strong return hits or chances to make a good anchor. Again there's a far superior homeboard.

3) 14/12*, 23/22. This leaves plenty of builders to fill the prime next throw. Moving 22/23 allows escape routes with 4s and 6s.

4) black must hit as white if far ahead in the race and can have faith in passing black completely without danger in the next few moves.

Black can't cover the 4 and I'm caught between 13/10 or 8/5 for the builder.

8/5 relieves pressure on the 8 point and covers more home points than 13/10. It leaves hits with (any 4 = 11),11,22,12,31,32, = 19 - of these only 11,22,41,42 (=6) make a double hit. 1s and 2s are also duplicated as white may need to use them to enter.

13/10 creates a builder to cover the 4. Hits are the same i think, 19. double hits are 1 less with 22,42,46 = 5

on ballance I think 8/5 is much stronger if my luck holds out so i move 14/13, 8/5.

5) 22/6 hopes to remove white's 13 point if she rolls a 4 which disconnects white's back anchor causing a lot of trouble. If white hits from the 10 with a 1 then we'll try again next time.

My 4 would is either 8/4 or 6/2 as 13/9 adds to much danger. 8/4 keeps more pressure on the 3 point if white decides to split

22/16, 8/4.

NinePointNinja said...

1) we can stay in the game for a while with our anchor, my play is all about avoiding the crunch. Waiting to cover the 4 pt is no problem. jumping up in the back helps circulation and u might upgrade the anchor.

23/21, 13/9

2) Here we can go 13/7 with the 6. First it unstacks the midpoint, and gives you a chance to re-establish a point in that quadrant. Having a spare on the 7 will help to continue with the blitz if not hit, and we will have more threats when we cube. Also with 13/7, we are duplicating 3s and specifically 3-1. Most times if he does roll a 3 (and choose to hit) we will have one or more return shots.

b/20, 13/7

3) Over the board id probly go 14/12 23/22. Thinking about it more, we could slot the 10 point and try to prime/gammon, but the chances dont seem great. By the time we make a prime we will have to dismantle it. 23/22 gives us a good way to play a 6, although its not a top priority at this point.

14/12*, 23/22

4)i love to be bold, but the hit here seems too bold. i think he hits a return shot 50% of the time, many of which result in gammons. it seems like it will be a double/take after any roll, so id rather have the cube in a racing game than in a blitz game where my opponent is much more likely to gammon than me.

8/5, 8/7

5)here we can just slot in his face with little risk, since we can win a bunch of 4 point games when he does hit.

13/7, 8/4


1. 23/21 to put this checker in a better place, then 8/4, improving our board.

Anyway there should be a double soon from white we may accept (position + race for white, but no threat except improving position).

Don't break the anchor, starting escaping checker, close race in whites favor (10 % i'll say), better board for us, no double already.

2. bar/20 then 13/7, duplicating 3's
All other 6 gives a lot more return shot

Better board for us, half of golden point made, more checkers back for us, 24/18 seems to dangerous for nothing, reasonnably no possible double for white after her next move.

3. I prefer to hit than to build.
If we build with 9/7 & 8/7, we can have a second checker back, and then maybe two on the bar (cause we have 3 blots...) and have white playing for gammon or doubling with a difficult decision for us.
White's already have an anchor, we have not. white has threats, we have position (for the moment...)

If we don't build, i guess we should hit to avoid real bad rolls in the next future (and real goods for white)

So i play : 14/12* & 23/22, putting our back checker in a better place.

Obviously we have a far better race than white.

4. Anyway our move, white may double next turn (but not sure...), so why putting us in a hard decision?
If we don't hit, good race for white, so clear double.
If we hit, poor board comparing to white, 3 blots, lots of direct and indirect shots for white, so possible frighting double and possible big crash if we accept.
Playing 8/4 improves our board (sure it's quite useless, regarding to race, except if white don't double...), avoid gammon possibilities and give us a reasonnable drop next move...i guess sometimes it's better to surely loose one point than reasonnably loose 2 or 4.

But what if we play to win? The cube is in the middle, it protects us from loosing too much...i guess i'll play 14/13* & 8/5, hoping white not doubling next scenario for us : white does not double, then does not hit, then we may double...and if white hits, we can drop her double later...

So in this position i guess the right idea is to be agressive and hope for good rolls and double decisions (in both sides) just after than accepting to loose one point instantly. We have nothing to loose.

5. The obvious 8/2 & 6/2 is weak (putting two checkers behind white's anchor), but after that white may not have a double next move (or it's an easy take), and all other moves stacks or exposes one blot or two.
We should not break our anchor (clearly two many return shots, too soon, we have an as good anchor as white and a closely better board)

Timothy Chow said...

I'm responding without reading the other comments first.

1. Black is ahead in the pip count even before the roll, 150 to 156, so running should be on his mind. 22/16 runs into a triple shot and breaks anchor, so it looks dangerous, but Black has a stronger board and White has a stripped and stacked position. Even if White hits, Black will usually have no trouble entering and will have plenty of return shots. The alternative is a quiet play like 23/21 8/4 or 13/9 6/4, but what is Black's game plan then? He doesn't have the time to play a 22pt holding game. 22/16 is my play.

2. I think we can eliminate 20/14 quickly. It doesn't unstack our tall point or get our rear checkers moving or avoid a double shot. A useful rule of thumb is that when we have more checkers back then 13/7 is often better than 24/18. Here, 24/18 has another strike against it: White's doublets all play extremely well because of Black's double exposure on the 18pt and 20pt. I'd play 13/7 here.

3. The choice seems to be between 23/22 14/12* and 9/7 8/7. My first instinct is 23/22 14/12* since it hits, disconnects White's position, and prepares to escape. However, looking more closely, I'm not so sure. The five-prime looks pretty strong. Still, I'll go with my original instinct of 23/22 14/12*. We are way ahead in the race so I think we should try to get our back checkers moving. We have an excellent shot at making the five-prime next turn anyway. But this is the problem I feel least sure about.

4. If we don't hit then 8/4 seems to be the obvious play. Then we will have 110 pips while White will have 98 pips. In a straight race that would be D/P. This is almost a straight race so I think we'll get cubed and the take will be doubtful. I'm going to assume it's a drop. With the Jacoby rule in force, nothing can be worse than that, so hitting seems clear. After 14/13* I think I play 4/1 despite its anti-positional look, because I think we need to cut down on White's shots.

5. Let's start with 10/6 10/4 as the default play to beat. I don't like any of the plays that use up spares and dump them behind White's anchor. Then the only other real candidate I see is 22/16 8/4. This is a bold play, but we do have the stronger board. Also, left to her own devices, White will likely make her 5pt or 4pt. 22/16 serves to distract White from that goal, forcing her to do something about her blot. To hit from the midpoint, she has to give up the midpoint. Finally, we'd rather use our checkers on the 10pt to make a useful point, and 10/6 10/4 gives up on that. I'd play 22/16 8/4 here.

Timothy Chow said...

Now that I've read the other comments, I realized that I didn't consider all the possible hitting plays in Position 4. So let's look at them all and count shots.

14/13* 4/1: 16 shots. Snake eyes triple hit.

14/13* 14/11: 17 shots. 4-2 double hits.

14/13*/10: 19 shots. 2-2, 4-2, and 6-4 double hit.

14/13* 8/5: 19 shots. 1-1, 2-2, 4-1, 4-2 double hit.

So my original vote of 14/13* 4/1 does minimize shots, but since 14/13* 14/11 leaves only one extra shot and doesn't bury a checker, I'm going to change my vote to 14/13* 14/11.

Also, I forgot to comment on whether White has a cube after we hit. I think she probably does but that we can take. The cube is probably clearer with the Jacoby rule in force.

I see that everybody seems to like 23/22 14/12* for Position 3, so since Paul says many of us will be surprised by it, I'm guessing that 9/7 8/7 will turn out to be correct. Still, I'm sticking to my guns with 23/22 14/12*.