Look at the West hand in the diagramed deal. With neither side vulnerable, South deals and opens one heart. What would you overcall?
Bridge-playing computer programs are getting better, but slowly. The latest world computer championship took place in Las Vegas during the Summer North American Championships. The 64-board final was contested by the programs that seem to be the strongest, Jack, from the Netherlands (jackbridge.com), and Wbridge5, from France (wbridge5.com).
Jack began with an 18 international match point advantage from the qualifying stage, but Wbridge5 won by 172 imps to 157.
Each program had its bidding and declarer-play successes, but the match was decided primarily because Jack lost heavily twice when it bid no-trump without a stopper in an opponent’s suit. First, it bid three no-trump with 10-9-8-6 of spades, losing five spades and the club ace. At the other table Wbridge5 bid and made four hearts to gain 13 imps.
Then Jack bid three no-trump with the singleton heart jack. Partner Jack drove into six no-trump, doubled and down five, losing six heart tricks. At the other table Wbridge5 bid and made six clubs to gain 19 imps, which was more than the winning margin. (Six diamonds was also unbeatable.)
Now to the diagramed deal. What would you bid over one heart? Humans would usually overcall two diamonds. They would have two eyes on three no-trump. If partner has the heart ace, the diamond ace and enough to hold spades, three no-trump will be laydown. When you have a good long minor, think of three no-trump.
But West Wbridge5 bid three diamonds, a weak jump overcall that would normally be based on a six-card suit. North Jack made a negative double, and South Jack bid three no-trump. After West Wbridge5 led the diamond king, the contract could not be made. South Jack could have escaped for down one, taking two spades, five hearts and one diamond, but it immediately played a club, so failed by three tricks.
At the other table West Jack jumped to four diamonds. North Wbridge5 doubled, which was negative but did not promise four spades. The double just said that its hand was too strong to pass but that it had no better call available. The higher a negative double is made, the fuzzier its definition. South Wbridge5, with nowhere to go, passed, converting the negative double into a penalty double. That contract had to fail by three tricks, declarer taking only six diamonds and one club.
Plus 150 and plus 500 gave Wbridge5 a 12-imp pickup.