the dorbel daily

Friday, 27 April 2012

Five Position Cube Quiz

Continuing with the theme of useful tools, I keep a collection of positions sorted by type. You might like to do this too if you find it useful. Today I have a little selection of positions that I have saved grouped together, although the connection isn't immediately obvious.

Position One.

Score, 0-0 to 5. Blue on roll. Cube action?

Position Two

 Blue leads 3-0 to 9. White is on the bar. Cube action.

Position Three.

Black leads 2-0 to 7. Cube action?

Position Four

Score 2-2 to 9. Black has two men on the bar. Cube action?

Position Five

Black leads 2-1 to 7. Cube action?

All the players in the matches where I saw these are strong, expert or world class level. They didn't play these well, can you do better? If you get them all right you will see what links them.
Oh yes, which style of board do you prefer?

I'll come back to these very soon, so post some answers in the comments please!
Until the next time, enjoy the game!


Timothy Chow said...

I much prefer the lower three board diagrams. The background is too loud in the first two diagrams.

1. The tough point for Blue to clear is 7 away from White's anchor so even if he's forced to leave a blot there, it's only an indirect shot. White has a strong board for now but she is way behind in the race and may be forced to break a point soon. I think only 66 and 43 are horror rolls; with some rolls, Blue will leave a blot on the 11pt but I don't think this is so bad. I double here and I'm not sure about the take. White may hit the indirect shot and even if she doesn't, Blue's 5pt gap may generate another shot for White later. She should be able to run off the gammon in most cases, if it comes to that. D/T is my guess.

2. Blue covers if he rolls an 8 but what if he doesn't roll an 8? If his rolls permits, I think Blue will be willing to break a point and kill a checker in order to clean up his blot on the ace point, since the cost of getting hit is high. If White then enters then White will have the advantage but if White dances then Blue will have the advantage. At a normal score, I think this would be D/T. Here, Blue is leading 6a9a and sending over a 4-cube risks getting an 8-cube sent back. Maybe I'm too chicken but I would wait a roll here. ND/T.

3. Black's outfield control is pretty powerful, and White has to roll a 1 and a 6 to escape. On the other hand, if White rolls a 1, will Black hit loose with a 4 or a 5? Not sure. It will break Black's five-prime, and White still has a four-point board. I probably wouldn't in most cases. Even if Black gets his checkers around before White rolls a 1, it's harder to roll a 13-checker prime than a 15-checker prime to complete the closeout. White is trailing in the match and she can certainly win a gammon from here. I'll go with D/T.

4. Black has a six-prime but he has two checkers on the bar. White has only a four-prime, but has decent chances of extending it, and has more time than Black. Black may well crack first. I think this has to be a take for White. The double is less clear to me. Suppose Black doesn't double, and then rolls 63, 53, 32, or 31, and then White dances. Can White take then? It looks bad but it's not totally clear to me that White has to drop. I'd hold the cube here. ND/T.

5. What's White's raw take point? If she drops she'll be trailing 6a3a for 29%; if she takes and wins she'll be leading 2a5a for 75%; if she takes and loses she'll be trailing 6a Crawford for 11%. That gives a raw take point of 18/64 or slightly more than the standard 25%. Recube vig looks close to money since Black's take point on an 8-cube is 25%. So White drops a little more quickly than for money but not by much.

Black actually trails in the pip count. Without doublets, both players will be off in 3 rolls if they miss once and usually off in 4 rolls if they miss more than once. Black seems more likely to miss more than once because of his gap on the 1pt. This looks close to a 4-roll position but with Black being slightly worse than he would be in a true 4-roll position. The take looks easy and I'm not sure about the double; I'll go with ND/T.

ah_clem said...

1) Even when blue leaves a shot, white still has to hit it. With the 11 point checkers 7 pips away from the anchor white is only 1 in 6 to hit a blot there. Assuming that one ever appears. And by the time blue is forced to leave a direct shot, whit's board should have crunched. Double/Pass.

2) AtS I calculate the raw takepoint as 6/23 which is slightly higher than for money, but not by enough to matter much. Gammons should be fairly rare.

Even if white manages to hit the blot, she still has a lot of work to do before claiming the win. Am I detecting a theme here? Assuming blue doesn't cover, white is 11/36 to hit, but 30% to hit doesn't mean 30% to win. She wins maybe half(?) after hitting for ~15% GWC.


3) White's only hope is to leap with a 61, but leaping doesn't equal winning since black has outfield control. Again, the raw takepoint is in the neighborhood of 25% (7/27) and white is nowhere close to that. With only one checker to bring around, gammons are few. Double/Pass

4)This is a bit harder than the previous three, since black risks having checkers trapped behind a four prime. If black enters and hits, his timing will be awful as white is likely to sit on the bar while his runners are stuck and his board crunches.
Alternatively, if black can hit and leap, his gammon chances are good.

Can White take here? Again, even when things work out well for white in the short term, there's still a lot of work to do before claiming the point. I'm not sure about the take, so that makes me apply Kit's law to say double.

I'm going to go with "pass" since that seems to be the theme, but without much confidence.

5) I calculate the redouble takepoint as 9/32 or about 28%. This is looking something like a 3 roll position which is double pass. But it's not quite a three roll position.

34 and 31 are disasters for black and he'll be cubed out. But that's only 4/36. All the other rolls position him nicely to bear off in two, so I'll say double here. And I'll say pass due to the elevated takepoint, but I'm not entirely sure about that.