Complex world of doubling

Backgammon Position:

This week we enter the complex world of doubling. There are four things to consider when doubling:

Race. Backgammon is fundamentally a race so whoever is winning the race is normally winning the game. There are obvious exceptions when you have checkers trapped behind an opponent’s prime but the race is a good guide.

Position. Who has the best static features in the position? This means things like home board points, anchors in your opponent’s board, primes or potential primes and the number of blots.

Threat. Do you have threats and in particular do you have threats, which if carried out, would mean that your opponent would no longer take next turn? A threat would be things like hitting a blot, making a key point in your home board, or extending/completing a prime.

Opponent. Unless you are playing a computer you need to take your opponent into consideration. How will he/she react to being doubled? Is he/she someone who drops takes or conversely takes drops?

The generally accepted view is that you should consider doubling if you are ahead in two of the first three elements and use the fourth element to help you make your final decision.

In the backgammon chouette from which this position was taken, white had erroneously played a 62 by moving 15/9, 3/1*. This minimised black’s shots to 15 instead of 18 after the correct 15/9, 15/13 but it exposed three blots instead of one.

Let’s evaluate the position.

Race: Black is behind 20 pips before the roll. Advantage white.
Position: Black has the stronger home board and an anchor in white’s home board. White’s position is something of a mess with too many checkers on his 1-pt and 2-pt. Advantage black
Threat: White has three vulnerable blots and if black hits one of them he may well pick up at least one of the other two. Black will win a lot of gammons because of his strong home board. Note also that white won’t be able to redouble black even if he should stay on the bar. The position is highly volatile as after nearly any hit by black white would be dropping next turn. Advantage black
Opponent: Not a big factor in this position as white is a good player who makes well-balanced cube decisions.

The key question is whether black wins enough gammons after hitting to make up for the fact that he is not favourite to hit from the bar. This can really only be judged from experience as it is nearly impossible to do over the board.

In the chouette the team correctly judged that they would win enough gammons and doubled. White correctly took, black rolled 12, hit the blot on white’s 1-pt, picked up the other two and won a gammon.

The Snowie rollout below confirms that both black and white made the right cube decisions.

Note that had white played his 62 correctly, 15/9, 15/13, and you then applied the criteria above you would find that black would not have had a double.

The key lessons:

Don’t expose unnecessary blots when your opponent has a strong home board.

Learn to use the criteria above to evaluate doubling decisions.

Chris Bray
03/2007