In KO matches slam decisions may make the difference between winning and losing, as many IMPs are swung. Aggressive robots set lower thresholds on slams and grand slams.
From the fourth quarter of the Micro Bridge vs. Wbridge5 semifinal match, an inferior grand slam reached and made by Micro Bridge.
| Board 57 North Deals E-W Vul | North ♠ J 7 6 5 ♥ 8 5 3 ♦ K 10 8 4 ♣ 10 5 | |
| West ♠ 10 3 ♥ A J 10 9 6 ♦ J 9 ♣ A Q 7 3 | East ♠ A K 9 8 ♥ K 4 ♦ A Q 5 ♣ K J 9 6 | |
| South ♠ Q 4 2 ♥ Q 7 2 ♦ 7 6 3 2 ♣ 8 4 2 |
| West | North | East | South |
| Micro Bridge | WBridge5 | Micro Bridge | WBridge5 |
| 1♥ 3♣ 4NT 5NT 7♣ | Pass Pass Pass Pass Pass All Pass | 1♣ 2NT 4♣ 5♦1 6♥2 | Pass Pass Pass Pass Pass |
opening lead ♦6
2NT shows 18-20 hcp (2NT opening is 21-22 hcp), 4♣ guarantees 4+ clubs and a maximum. With West placing East with Kx(x), and using double dummy simulation which always finds the heart queen, it determines that 7♣ is a good prospect. In the play Micro Bridge wins the diamond queen, pulls trump and plays heart king and heart finesse, +2140.
Board 5 from the first quarter of the Final KO was not a slam deal even though twelve tricks were taken at both tables when covering an honor with an honor was wrong.
| Board 5 North Deals N-S Vul | North ♠ 7 6 ♥ 5 2 ♦ Q 8 4 3 ♣ A Q J 10 9 | |
| West ♠ A K 10 8 5 ♥ A J 10 9 7 ♦ 5 ♣ 3 2 | East ♠ Q J 4 3 ♥ Q 6 ♦ J 10 9 7 ♣ K 8 6 | |
| South ♠ 9 2 ♥ K 8 4 3 ♦ A K 6 2 ♣ 7 5 4 |
| West | North | East | South |
| Synrey Bridge | Micro Bridge | Synrey Bridge | Micro Bridge |
| 1♠ 2♥2 4♠ | Pass Pass Pass All Pass | Pass 2♣1 2♠ | Pass Pass Pass |
Opening lead ♥5
| West | North | East | South |
| Micro Bridge | Synrey Bridge | Micro Bridge | Synrey Bridge |
| 1♠ 4♠ | Pass Pass All Pass | Pass 3♠ | Pass Pass |
At both tables 4♠ made twelve tricks when the heart queen was covered by the king. On this deal it’s only 1 IMP, but in a similar situation the same play might make the difference of game or slam. At one table, with Synrey Bridge West declarer, having bid 1♠ and 2♥, the lead of the heart five was unlikely to be from J(or 10) 7 5, and even then declarer would likely assume it wasn’t led from the king and therefore not play the queen, but duck to its A J (or 10) 8 2. Micro Bridge would not cover the heart queen if it knows West has five hearts. Here , but a simulation analysis does not take into account partner’s or declarer’s choice of plays, and on balance plays partner for jack or ten third more often than two small. Here we see that Micro Bridge does not draw inferences based on the previous bidding and play, as Q-Plus Bridge does in board 41 below.
At the other table, Micro Bridge pulled two round of trump then led the heart queen. Declarer could be trying to fool South into not covering when declarer doesn’t have the jack, but, if missing heart honors, that might not be as good a play as leading up to the queen, and covering will lose a trick if declarer has one less small heart and one more small club.
The defense of this deal shows that Micro Bridge and Synrey Bridge did not draw an inference based on the previous bidding and play, as referred to above. Interestingly, Q-Plus Bridge does draw such an inference as declarer on board 41 below.
An interesting play problem in the third quarter of the semifinals.
| Board 41 North Deals E-W Vul | North ♠ K J 10 2 ♥ 10 ♦ Q 3 2 ♣ Q J 10 5 3 | |
| West ♠ Q 5 4 ♥ Q 9 5 ♦ 10 6 4 ♣ A 8 6 4 | East ♠ 9 6 ♥ A 8 7 6 4 2 ♦ K 9 8 5 ♣ 9 | |
| South ♠ A 8 7 3 ♥ K J 3 ♦ A J 7 ♣ K 7 2 |
| West | North | East | South |
| Synrey Bridge Q-Plus Bridge | Q-Plus Bridge Synrey Bridge | Synrey Bridge Q-Plus Bridge | Q-Plus Bridge Synrey Bridge |
| Pass Pass | Pass 2♣ 4♠ | Pass Pass All Pass | 1NT 2♠ |
Q-Plus Bridge declarer won the diamond jack at trick one. Assuming no quick ruff, a human declarer’s plan would be to take the trump finesse toward the safe hand, that is, toward the hand that has the diamond king. If it loses there may be time for declarer to set up the clubs for a diamond pitch as a diamond cannot be safely returned. Generally a robot’s analysis would result in taking the trump finesse equally each way as it would not place the diamond king in one hand more than the other. However, here Q-Plus Bridge adds to its ‘thinking’ process the tendency of a defender, given the auction, to choose a safe opening lead, so hands with the diamond king and without a heart or club honor are reduced in probability. With East more likely to hold the diamond king the finesse of the trump queen is taken against West, +450.
Synrey Bridge makes no such inference, and with an equal chance each way, takes the finesses king and jack toward the ace, losing to the queen, and with a diamond return, down one.
In the other match, with the same auction, Micro Bridge led the ♦4 against Wbridge5’s 4♠ contract. Wbridge5 takes the losing trump finesse, and with a diamond return, is down one, -50.
| West | North | East | South |
| WBridge5 | Micro Bridge | WBridge5 | Micro Bridge |
Pass Pass | Pass 3♥ 4♠ | 2♥ Dbl All Pass | 2NT 3♠ |
At the other table, against Micro Bridge’s 4♠ contract, a heart opening lead by Wbridge5 to East’s ace and a club to the ace and a club ruff. Declarer won the diamond return with the ace, and played three round of trump, finessing against West, +420.
Aggressive and accurate slam and game bidding was one reason Micro Bridge excelled in this year’s championship.
Two possible grand slam deals from the 2nd round robin match follow.
| Board 17 North Deals None Vul | North ♠ Q 5 2 ♥ K Q 10 8 ♦ 3 ♣ J 10 7 6 4 | |
| West ♠ J 10 9 4 ♥ 7 5 ♦ A K Q 9 4 2 ♣ 8 | East ♠ — ♥ A J 9 4 3 ♦ J 7 6 5 ♣ A K Q 2 | |
| South ♠ A K 8 7 6 3 ♥ 6 2 ♦ 10 8 ♣ 9 5 3 |
| West | North | East | South |
| Micro Bridge | TCS BridgeBot | Micro Bridge | TCS BridgeBot |
| 2♦ 4NT 5NT | Pass 2♠ Pass Pass | 1♥ 4♠1 5♥2 6♦3 | 1♠ Pass Pass All Pass |
Opening lead ♦4
Declarer ruffed three spades in dummy, +940. In the other two matches, only Q-Plus Bridge reached 6♦.
Let’s see Micro Bridge’s slam bidding methods. 4♠ showed a singleton or void in spades, 4+ diamonds, and 15+ hcp. 5NT is asking for kings, assuming East has a spade void, which a simulation predicts 59% of the time. If two kings, West will bid the grand slam, as it will assume a void (59%) and can ruff three spades in dummy. With East showing one king, West rests in 6♦. With limited bidding space, the best way to decide on 6♦ or 7♦ might be to rely on the probability of the void and check for two kings.
Board 20 was another possible grand slam decision.
| Board 20 West Deals Both Vul | North ♠ J 10 7 2 ♥ Q 6 3 2 ♦ A Q J 9 ♣ 5 | |
| West ♠ 5 4 ♥ J 9 4 ♦ K 10 4 ♣ Q 8 6 4 3 | East ♠ 9 8 3 ♥ 10 7 5 ♦ 8 7 6 5 2 ♣ J 9 | |
| South ♠ A K Q 6 ♥ A K 8 ♦ 3 ♣ A K 10 7 2 |
| West | North | East | South |
| TCS BridgeBot | Micro Bridge | TCS BridgeBot | Micro Bridge |
| Pass Pass Pass Pass Pass Pass All Pass | Pass 2♠2 3♦ 4NT 5♦4 6♠ | Pass Pass Pass Pass Pass Pass | 2♦1 3♣ 3♠ 5♣3 5♠5 7♠ |
opening lead ♥5
Micro Bridge’s slam methods include guaranteeing all the key cards if asking for trump queen. South, placing North with 4+ spades, the diamond ace and at least one queen, bids the grand slam. If you play trumps to be 3-2, then ruffing two clubs high in dummy will guarantee the contract. However, Micro Bridge pulled three rounds of trump, and with hearts 3-3 needed to guess which way to pick up two diamond tricks, and guessed wrong, -100.
Board 8 of the fifth round robin is a possible slam. Let’s examine the methods and ‘thinking’ of a few of the robots in coming to a final contract.
| Board 8 West Deals None Vul | North ♠ Q 10 8 5 ♥ A Q 10 4 3 ♦ A 7 5 ♣ 7 | |
| West ♠ J 3 ♥ 9 8 7 6 ♦ Q 9 ♣ K Q 9 4 3 | East ♠ 9 7 4 ♥ J 5 ♦ 10 8 2 ♣ A J 6 5 2 | |
| South ♠ A K 6 2 ♥ K 2 ♦ K J 6 4 3 ♣ 10 8 |
| West | North | East | South |
| RoboBridge | Synrey | RoboBridge | Synrey |
| Pass Pass Pass Pass | 1♥ 2♠ 4NT 6♠ | Pass Pass Pass All Pass | 2♦ 3♠ 5♥ |
South 2♦ and 3♠ bids showed a good hand with extra hcps or good controls and 4 spades. North’s simulation assumed 15+ hcps or more first and second round controls and safe to be at the five level, so 4NT fetched a key cards and the slam was bid.
| West | North | East | South |
| Micro Bridge | Q-Plus Bridge | Micro Bridge | Q-Plus Bridge |
| Pass Pass Pass Pass All Pass | 1♥ 2♥ 4♣1 5 ♠ | Pass Pass Pass Pass | 2 ♦ 2 ♠ 4NT 6♠ |
North’s 2♥ bid does not deny 4 spades, and 4♣ makes it easy for South to check for controls. If North had bid 4♠, the auction would have ended, as it did in Micro Bridge’s auction: 1♥ – 1♠. 2♠ – 4♠, Pass and Wbridg5’s auction, 1♥ – 2♦; 2♥ – 2♠; 4♠ – Pass (2♠ by North needs 17+ total points).
An excellent grand slam in the fifth round robin was only reached by Wbridge5.
| Board 32 South Deals N-S Vul | North ♠ J 6 2 ♥ J 7 ♦ 9 6 ♣ K Q 10 9 6 2 | |
| West ♠ A K 10 8 3 ♥ A K 8 5 3 ♦ Q 10 8 ♣ — | East ♠ Q 9 5 4 ♥ Q 4 2 ♦ A K J 2 ♣ J 7 | |
| South ♠ 7 ♥ 10 9 6 ♦ 7 5 4 3 ♣ A 8 5 4 3 |
| West | North | East | South |
| WBridge5 | Meadowlark | WBridge5 | Meadowlark |
| 1♠ 3♥2 5♣4 6♠ | Pass Pass Pass Pass | 2NT1 4♦3 5♥5 7♠ | Pass Pass Pass All Pass |
East’s 7♠ based on simulation with 19+ total points including club void, +1510.
World Computer-Bridge Championship 