the dorbel daily

Monday 17 October 2011

More Answers For The Famous Five

These are the rest of the answers to the Famous Five Quiz. If you haven't seen that, go back two posts.
Here's Position 3. It's a money game and White has the cube, Black to play 2-1.

I really like this one, because it illustrates a point that many players overlook. All our panel went for 24/22, 14/12*. Alertly they had all spotted that this gives Black sixes and fours to escape, as well as several combinations of numbers to make the bar point. To be honest, I might have made this play too, but it is in fact an error, costing 0.05. Why so? Because it ignores the fact that before we can carry out our threats to escape or make a five prime, White gets a turn. The panel's play works brilliantly when she dances, but when she enters she has 21 numbers to hit Black off the 3pt. Her board is as strong as ours and she has an anchor, we don’t. When that works for her, our blots in the outfield are a liability, not an asset. When we stay back and button up in the outfield with 14/12*/11, she doesn’t have any of these options. With some numbers (64, 44, 42, 41 probably) she will hit us off the 2pt, but that is in any case less dangerous than being hit on the 3pt.
This is not by any means a typical position. The diversification that seduced the panel is a good basis for attacking any problem. It doesn't arrive at the right answer here, but we all might have got it if we had taken the trouble to think about what White's roll might contain.
Oh yes, how does making the five prime look? It looks like a double whopper with fries. Life threatening.

Then we come to position 4, with Black to play 3-1. Black must hit of course and look around for a three. Actually I say "of course", but one of the panel chose 8/5, 8/7. This blunder won't do. Black can't really hope to keep White at bay with that weedy 14pt anchor, although he will have a take when White doubles.
How did the rest do?

Two of them chose 14/13*, 8/5, nicely diversifying the 8pt stack. This leaves 19 return shots at three blots, 3 of which double hit. Our fourth panelist chose 14/13*, 4/1, keeping the shots down to 16 with only one double hit. This is of course good, but the ace point is just not where you want your blot to be. Both these plays are blunders. White should double from the bar and Black will have an unpleasant take. Our last man standing went for 14/13*/10, alertly giving himself sixes as another cover for the 4pt. Again though, just like position 2, White gets to play first and this play gives up 19 shots, including three double hits. Actually it's five, but White won't double hit with 4-2. This play is much better than the rest, except for the best play of all, which is 14/13*, 14/11. 17 shots and two double hits and this combination is the winner. After any play White should double and Black will have a take, fairly easy after a good play and unpleasantly close to a pass after a bad one.

Position 5, with Black to play a 6-4.

One panellist opted for the "safe this turn" play 8/2, 6/2. It's not a bad play, but it burns two of Black's three spares in order to make a weak point behind the anchor and leaves Black with TMP, Too Many Points. Avoid making seven points if you can. It's very inflexible and leaves you with a lot of numbers that leave a shot next turn. Another tried 13/7, 8/4, which got my vote too, pretty positive and with lots of returns if White can hit. However, it doesn't address the main feature of the problem, which is that Black is going to have to leave his anchor in order to get into a doubling position and with this roll he should try it now. He has a small lead after the roll and a better board, but the main argument is that this is just the least bad 6! If he is going to leave shots, it may as well be in pusuit of his main aim, which is escape. One panellist went for the wide-open 22/16, 13/9, but best of all is 22/16, 8/4, the choice of two of our guests.

Many thanks to those brave souls who put their opinions on the line for us, heroes all. Why don't you have a go too, the next time we have a quiz?

Until the next time, enjoy the game!


Timothy Chow said...

In Position 4, you may have overlooked the fact that I changed my vote to 14/13* 14/11 after looking at other people's comments.

Position 3 is fascinating! You were right that it surprised many of us. I will have to study it further to see if I agree with your explanation of why 14/12*/11 is best.

Timothy Chow said...

I looked at GNU's temperature map for Position 3 and it confirms your analysis that White's return shots from the bar are the decisive factor here. 23/22 14/12* isn't all bad because White's 6's from the bar are worse after 23/11 14/12* than they are after 14/12*/11, but the hits more than compensate for that, especially White's 33 and 22 jokers.

I also found it useful to consider the variant position obtained by moving Black's checker on the 11pt back to the 14pt. In this variant, Black will still hit with 14/12* of course, but now he can't make an outfield point and must choose between shuffling an outfield blot or playing 23/22. A truncated rollout suggests that these options are roughly equal. I think that either 14/13 or 12/11 is a somewhat productive use of the ace since 14/13 builds on the bar point and 12/11 unduplicates Black's 5's. Thus 23/22 is also on balance a somewhat productive ace—just not a good idea in the original position when there's an attractive alternative of cleaning up the outfield blots.

Timothy Chow said...

One more comment about Position 3: I looked at the variant obtained by moving one of White's spare checkers on her 6pt back to her 10pt. In this variant, 14/12*/11 is still probably best, but the decision is a lot closer. White's counterattacking potential has been reduced and, in particular, her 33 and 22 are not quite as powerful responses to 23/22 14/12* as they are in the original position.

Julia said...

Something went wrong and my answers didn't get submitted! Ah well...

(3) I'd have agreed with the panel. The bar looked tempting and had White only two men back, therefore abandoning the anchor to hit on 11, I'd have gone with it.

(4) I'm going to look smug - I saw all the extra double-hits and picked the winner. Honest, guvnor.

(5) I was with you on this one, 13/7 8/4. The step into the outfield looks just too dangerous. Perhaps I play too much against bots who seem able to get a successful blitz from nowhere...