the dorbel daily

Wednesday, 14 November 2012

The Big Hammer

The 4 cube is the bg equivalent of the Mighty Hammer of Thor, deadly in the right hands. The player prepared to ship a 4 cube at the first opportunity will wreak havoc at all levels below World Class. The possesion of the cube can be worth a lot, but only if you are prepared to use it! In a recent match I had two opportunities to use it. Here's the first.
You are Black, holding the 2 cube in the first game of a 9 point match. What's the correct cube action for both sides here?

The first question to ask yourself, always, is "If I was White, am I 100% certain that this is a take? If not, it must be a double." This is known as Woolsey's Rule. Pretty clearly you can't be certain that this is a take, with two men on the roof against a four point board, so Black is good enough to redouble. Now move on to question two. "Am I 100% certain that this is too good to double? If yes, play on for the gammon for at least one roll, if no, turn the cube." This is known as dorbel's rule. Purists don't like this rule, but in practical terms it performs quite well.
So, what's the answer? This is a correct redouble and a correct pass, even though Black's checkers are not well placed to close the board and he still has one checker behind a five prime. Failing to cube or taking the cube are both small blunders costing about 1/10th of a point.
Dorbel's rule works quite well in situations where the decision to cube or play on isn't clear, because if you get a pass it puts two concrete points onto the scoresheet and when you get a take in this position , as you often will, you gain 2/10ths of a point in theoretical equity. Actually you often get takes in positions much stronger than this and passes in positions that are much weaker. The point of cubing, often missed, is that it allows your opponent the opportunity to make a mistake. The Mighty Hammer of Four is a terrifying weapon.
 The big temptation is to play on in the hope that if things go well you will win a gammon and if things deteriorate, you'll be able to cash later. That's often the case of course, but it's easy to see here that an "ordinary" number for Black, 5-3 say, followed by the same number for White will leave Black in a position where not only can't he cash, but he won't even have a redouble!
I failed to redouble that one, forgetting my own rule! TIP:More mistakes are made by forgetting the things that you already know than are made from technical ignorance.

Later on I led 4-2 to 9 and holding the cube, got down to this juicy position.

Uneven distribution and different numbers of checkers, so we can't rely on formulae that only count the pips. Black will usually waste a lot of pips here, initially when he throws sixes or fives and later when he gets down to only checkers on the two and one points. White on the other hand will use all her numbers efficiently at first, as even a 3 will fill her gap nicely. She also has two extra checkers off and less wastage on the lowest points. Black though has two things going for him. He gets to roll first and all the lower doublets are much better for him than they are for White. He is a lock to be off in six rolls and to win without doublets White will need to get off in five rolls. She'll have to roll pretty well to do that, so this might be a redouble so I did a Thorp Count . This old fashioned formula is very easy to apply and if you make some little adjustments for gaps, can be very accurate.
Actually here, Thorp rates this as an initial double but not a redouble and given that Black leads in the match he should be a little more conservative than usual in bringing a large cube into play. Nevertheless, making a small adjustment for White's gap makes a difference. Also, Black will get some incorrect passes here and with the end of the match so close, White's opportunities to redouble to 8 are going to be limited, so I finally turned it and White correctly took. Both actions are correct.
Note that Woolsey's Rule still works here. I couldn't be certain that this is a take for White, fairly confident yes, 100% certain, no. If the cube dies with this turn, at 0-0 to 3 say, this position is a marginal take/pass, so a useful reference position.
When you take a 2 cube, part of your equity lies in your willingness to use it if things go your way. Don't be afraid to use it! Swing that Mighty Hammer and reap the rewards.

Friday, 9 November 2012

In The Spotlight Again.

In the previous post, we saw how the bold play was correct, even though it enhanced the match leader's gammon risk. Winning the game is a very good way of not being gammoned! UK expert Rick Janowski points out that in fact in these situations the money play is usually correct and that it is a very common mistake to over-estimate gammon danger for the leader.
Today it was my turn in the spotlight, playing for UK against Moldova in the Inter-Nation Cup on GridGammon. I led throughout the match, so played a number of games where I was keen to keep the opponent's gammon chances down. This one came when I led 8-5 to 11.

I rejected 6/1, 5/1 and I hope that you would too. Burning two spares and leaving the problem of how to  clear the 8pt is not the way to go. Black has to make a bold play while White is on the bar. I went for 8/3, 5/1 leaving five fly shots for White, but this is still not bold enough! The money play, 8/3, 6/2* is best, essential to stop White from making the 23pt anchor next roll. It's so easy when the winning post is in sight to try and avoid the last minute turnaround, particularly when White has such a good board, but it's right to leave eleven shots here and the match play is a smallish error.

Allowing for gammon losses is much more important when the cube comes across. Here's a good example that came when I led 8-2 to 11. White doubles, is this a take?

For money this isn't too hard. Black will at worst have an ace point game to fall back on. This isn't enough for a take on its own of course, but added to his other chances it makes for a pretty easy take. Here though, the cube is worth somewhere between next-to-nothing and not-a-lot and a gammon loss is very serious. XG++ will pass it, as did I , but a rollout indicates that it might be an ultra close take! Good reference position if you save them. Take or pass, this one loses Black one point, always after a pass, on average after a take. If you feel that the position is a marginal take/pass like this, which side should you plump for? Conventional wisdom suggests take, so that your opponent has to play for his point, rather than being handed it on a plate. If you think that you are clearly the better player this makes a lot of sense, as White in this position may well make some mistakes on the way home that will boost your equity a bit. If on the other hand you are the weaker player, it might make sense to bin this one and wait for a better opportunity later. You want to escalate the cube in a relatively skill free environment.
Until it's your turn in the spotlight, enjoy the game!

Thursday, 8 November 2012

In The Spotlight.

Picture the scene. It's an important match, there are watchers and worse still, it's a team event. You are in the spotlight and and you get an ultra tough roll. Even the strongest players can blunder here. Look at the position below. Black, a strong expert, leads 10-8 to 11, post-crawford, after at one stage leading 10-3 Crawford with one point left to clear for victory. All of this adds up to pressure, particularly now he's reached this score and a gammon loss is the match lost.

White is on the bar and Black rolls 5-2. The cube is dead, the gammon threat is one way and the obvious hitting play and the more adventurous double hit are suddenly not so appetizing. What should Black do?
The first plan to abandon is 8/1 to cover the blot and make a three point board. This burns Black's major asset, his broken five prime and it isn't even very safe, leaving 14 indirect shots. It does of course give White nine numbers to dance as well, but she won't be worrying to much about that I think.
Black actually tried 15/8, keeping his prime, adding a builder and cutting the shots down to eleven. He succumbed to the temptation of keeping the anchor as security, because of gammon fear and possibly, the very common failing seen at all levels of not wanting to put the match on the line now.
One of the best ways to avoid the gammon is to win the game! After hitting, Black is the clear favourite (56%) to win the game. After the quiet play he is the clear underdog (40%). He'll lose 23 gammons after the hitting play, but he still loses 15 after playing quietly. It's no contest and 15/8 is a big blunder, cutting his match winning chances by about 4.3%
The best play is 23/18*, 15/13, keeping the shots down to 12 and quite importantly, knocking away White's valuable slot for the bar. It does of course expose Black to the danger of being closed out after a hit, but White doesn't have much in place to go for that after she has two checkers on the bar. Even when she enters those, they are fairly well primed. 
When it's your turn in the spotlight, be brave! Play to win, not to avoid losing. Black here is in a poor psychological state to play aggressively. He had the match all but won half an hour ago and he has been on the defensive ever since as game after game has leaked away. When you find yourself in this sort of position, which you will one day, try to think like a predator, not a prisoner.
Until the next time, enjoy the game!