The 12th annual World
Computer-Bridge Championship, recognized and supported by the American Contract Bridge League
(ACBL) and World Bridge Federation (WBF) was held in Las Vegas, Nevada, USA
alongside the ACBL’s summer North American Bridge Championship (NABC).

History

The ACBL inaugurated an annual
computer-bridge championship in 1997, and in 1999 it became an ACBL/WBF joint
venture.Since its inception in 1997,
the championship has been held every year alongside an important bridge
championship.The twelve championships
have been held five times at an ACBL NABC, six
times at a WBF World Championship and once at the European Bridge League’s first
European Open Championship.For a
complete history and details of previous championships go to www.computerbridge.com or www.ny-bridge.com/allevy/computerbridge

Technical remarks

A bridge “table” consists of a central server (CS) that
manages the game, and four connecting computers that “seat” the robots.The CS manages and records the play.Play proceeds
automatically, with pauses for manual exchanges of information when explanations of
bids are necessary.The CS distributes
the hands, receives and
passes information from and to the robots and records the bidding and
play.This year Intel Core 2 Duo
2.4GHz/2GH Ram desktops were used, running under Windows XP Pro.The timing of play was set at two minutes per pair per deal.

The contestants submit their robot's Convention Card (CC)
containing their bidding and carding methods, at least one month before the competition
so that the other competitors can prepare.This
information is stored in the opponent robot's memory before play begins.Nevertheless, during the bidding there are
some situations where bids are alerted and explained, and the meaning manually input into
the opposing robots' memory.

Without getting into
the details at this moment, most of the robots are programmed with a combination of
knowledge-based AI (sets of rules) and search-based AI (simulations).

Play format

The format is team play.Two teams play each other, with each team using four identical robots,
one pair sitting North-South at one table and their teammates sitting East-West at the
other table.

This event starts with a
32-board round-robin, a seven round affair with one bye each round.The top four robot teams advance to the
knockout stage, a 64-board semifinal followed by a 64-board
final.The round-robin is scored on an
International 30-VP scale.

A
new Individual event was introduced this year. A one-day, 8-robot
Individual was held with Blue Chip Bridge joining the seven robots competing in
the major championship.

The round-robin ended with Jack
topping the field, followed by Shark Bridge, Wbridge5 and Micro Bridge. Jack’s results are impressive,
winning all its matches, and scoring 155 VPs out of a possible 165 VPs.
The semifinals pitted Jack, with an 16 Imps carryover, against Micro Bridge and
Shark Bridge playing even against Wbridge5.

Team
vs. Team

Shark
Bridge

Bridge
Baron

Micro
Bridge

Jack

Wbridge5

Q-PlusBridge

RoboBridge

Total

Position

SharkBridge

IMPs

bye
rd 7

VPs15

102-30

rd
1

25-4

108-46

rd
2

25-5

50-69

rd
3

12-18

52-115

rd
4

5-25

87-83

rd5

16-14

117-52

rd
6

25-5

123

(Q-2)

Bridge
Baron

30-102

rd
1

4-25

IMPs

bye
rd 2

VPs15

58-77

rd
3

12-18

30-99

rd
4

5-25

82-79

rd
5

15-15

63-78

rd
6

13-17

95-52

rd
7

22-8

85

(6)

MicroBridge

46-108

rd
2

5-25

77-58

rd
3

18-12

IMPs

bye
rd 4

VPs15

31-83

rd
5

7-23

58-66

rd
6

14-16

90-39

rd
7

23-7

89-71

rd
1

18-12

100

(Q-4)

Jack

69-50

rd
3

18-12

99-30

rd
4

25-4

83-31

rd
5

23-7

IMPs

bye
rd 6

VPs15

98-44

rd
7

24-6

129-25

rd
1

25-0

151-35

rd
2

25-0

155

(Q-1)

Wbridge5

115-52

rd
4

25-5

79-82

rd
5

15-15

66-58

rd
6

16-14

44-98

rd
7

6-24

IMPs

bye
rd 1

VPs15

86-70

rd
2

17-13

108-66

rd
3

22-8

116

(Q-3)

Q-Plus
Bridge

83-87

rd
5

14-16

78-63

rd
6

17-13

39-90

rd
7

7-23

25-129

rd
1

0-25

70-86

rd
2

13-17

IMPs

bye
rd 3

VPs15

167-56

rd
4

25-0

91

(5)

RoboBridge

52-117

rd
6

5-25

52-95

rd
7

8-22

71-89

rd
1

12-18

35-151

rd
2

0-25

66-108

rd
3

8-22

56-167

rd
4

0-25

IMPs

bye
rd 5

VPs15

48

(7)

Table 2.Round Robin results.

In the semifinal matches, Jack,
starting with a 16 Imp carryover, defeated Micro Bridge, 166-112, and WBridge5 narrowly defeated Shark Bridge,
139-121.WBridge5 overcame an
18 Imps carryover to defeat Jack, 172-157, in the finals, and repeated as world computer-bridge
champion.

As an interlude between the round
robin stage and the knockout stage, a 2-table, 8-robot,
112-board Individual was played. Shark Bridge won the event with a 53.13%
score.

Robot

56
Average

1

Shark Bridge

59.5

53.13%

2

Bridge
Baron

57.5

51.34%

3/4

Micro Bridge

56.5

50.45%

3/4

Q-Plus
Bridge

56.5

50.45%

5

Wbridge5

55.5

49.55%

6/7

Jack

54.5

48.66%

6/7

Blue Chip Bridge

54.5

48.66%

8

RoboBridge

53.5

47.77%

Table 3. Individual results

While the robots never exhibit bidding misunderstanding when playing with an
identical copy of themselves, many misunderstandings occurred in the
Individual, where robots played with 'strangers.' One difficulty was that, even though a relatively simple common Convention Card
was used, not all situations and bidding sequences were covered in their entirety. If two human
first-time partners used a simple Convention Card, without much discussion, they would
draw on their experiences when a situation they hadn't discussed or couldn't
remember, occurred. For
example, the humans would assume that fourth suit was forcing, at least for one round.
In a similar situation, robots might pass a fourth-suit bid, having no
'experience' to draw on. The
final results were extremely close, with less than a 5.5% difference between first and
last place. This suggests that the results were random, matching the
randomness of the play. This was an instructive event, and hopefully will
be repeated with more care and more success, next year. Not withstanding these issues, congratulations to
Shark Bridge for winning the first Individual.

How
robots 'think' during the play of the hand

One of the AI methods used to
program bridge-playing robots is a double dummy simulation technique in which
the unknown hands are constructed, many times over, consistent with the bidding
and play, and each construction is analyzed double dummy. If only this
technique is used in the play of the cards, at each trick the card that has the
best chance of achieving success (making the contract as declarer or defeating
the contract as defender), as determined from this analysis, is played.

Watch Wbridge5 use this technique on the following deal from the round robin,
hands rotated.

Round 4. Board 6. Dealer South. Vulnerable N-S.

♠

A 7 4♥ A 9 5♦ A K Q 3
♣ Q 9 6

♠

Q 5♥ 6♦ J 9 8 6 5
♣ J 8 7 5 2

♠

J 9 6 3 2♥ Q J 8♦ 10 2
♣ K 4 3

♠

K 10 8♥ K 10 7 4 3 2♦ 7 4
♣ A 10

West

North

East

South

Shark Bridge

Wbridge5

Shark Bridge

Wbridge5

-

-

-

1♥

Pass

2♦(1)

Pass

2♥

Pass

3♥

Pass

4♥

Pass

4NT

Pass

5♥(2)

Pass

6♥

All Pass

(1) Game forcing(2) 0 or 2 key cards without the
trump queen

Against 6♥ by Wbridge5, Shark Bridge led
the ♠Q. If trumps are 2-2, the slam is cold and if
there is a trump loser, then there are squeeze possibilities with threats in the
other three suits. The play requires that declarer 'best’ guess which
distributions to play for.

Wbridge5
won the ♠K
in hand. A double dummy simulation determined that the contract could be made,
double dummy, against more distributions of the opponents' cards by winning the king in hand than by winning the ace in
dummy. A heart was played to the ace and a heart returned to the jack and
3 — Wbridge5 ducked the heart! A simulation, at this point, determined
that the contract could always be made, double dummy, if hearts are 2-2, and could be made,
double dummy, more
often by ducking than by winning the king when trumps are 3-1. East returned the ♦10.
Wbridge5 won the ♦A in
dummy, led a heart to the king and ran hearts coming down to the following
position.

♠

A 7♥ -♦ K Q 3
♣ 6

♠

5♥ -♦ J 9 8
♣ J 8

♠

J 9♥ -♦ 2
♣ K 4 3

♠

10 8♥ 4♦ 7
♣ A 10

Now it was up to Wbridge5 to determine the end position. A simulation
is done for each card played. On the ♥4,
West discarded the ♠5 and Wbridge5 got it right by
discarding the ♠7 from dummy. Now a spade to
dummy's ace squeezed West. West blanked the ♣J, needing to keep
three diamonds. Then the ♦K
and ♦Q squeezed East
into keeping the ♠J and the lone ♣K and
declarer pitched the ♠10. Wbridge5 now won the last
two tricks with the ♣A10, for 1430.

A further step in robotic 'thinking'
is to use single dummy techniques, which allow for the both sides going wrong,
i.e., not playing double dummy. To that end, a robot places itself in an
opponent's seat and uses a variety of schemes to analyze the best play.
Generally, these schemes are either rule based, as opposed to simulation based,
or a combination of a double dummy simulation with rule based corrections. It
is noted that using a 'pure' single dummy
simulation, for each construction of the missing cards, is currently
too inefficient, i.e., too time consuming.

In the following hand, the use of a single dummy technique helped Shark
Bridge defend best.

Round 1, Board 8. Dealer South. Vulnerable
None.

♠
A Q 9 8 6♥ 8 4♦ Q J 9 5 2
♣ 2

♠
5 4♥ Q 10 9 7 5 3♦ 6 3♣ Q 7 6

♠
J 10 3♥ A 6 2♦ K 10 8
♣ A 10 8 5

♠
K 7 2♥ K J♦
A 7 4
♣ K J 9 4 3

West

North

East

South

Shark Bridge

Bridge Baron

Shark Bridge

Bridge Baron

-

-

-

1NT

Pass

2♥(1)

Pass

2♠

Pass

3NT

Pass

4♠

All Pass

(1) Transfer

In all three round robin matches (Wbridge5 had a bye), 4♠
was the contract, played five times by South and once by North (by Micro Bridge,
playing weak NT). When Shark Bridge defended against Bridge Baron, on the
lead of a club Shark Bridge East went up with the ♣A and returned the
small heart. Declarer guessed wrong, playing
the ♥J, and went down, losing two hearts, the
♣A and a diamond.

At the other five tables, the defense failed to give declarer a
chance to go down by neither underleading the ♥A
nor ducking it when declarer led a heart from the North hand. The reason
that a single dummy technique is needed to defend best in this
hand, is that using only a double dummy simulation, which assumes that
the opponents play as if they see all the cards, ducking or underleading the ♥A
can never win. While many of the robots employ single dummy techniques,
only Shark Bridge got this defense right.

BiddingThe robots never forget their system, so using involved treatments, within
the parameters of the conditions of contest, can often prove
beneficial. Look at the following hand from the finals, a
25-high-card-point grand slam. While Wbridge5
did well to reach 6♦,
Jack did even better, reaching the lay-down grand using a system perfect for
these hands.

Board 14, 4th quarter. Dealer East.
Vulnerable None.

♠

-♥ A 9 5 3♦ J 10 9 5
♣ Q 9 6 5 2

♠

K 10 8 7 2♥ Q J 4 2♦ Q
♣ 10 8 3

♠

Q J 6 5 3♥ 8 7 6♦ 4
♣ K J 7 4

♠

A 9 4♥ K 10♦ A K 8 7 6 3 2
♣ A

West

North

East

South

Jack

Wbridge5

Jack

Wbridge5

-

-

Pass

2♣(1)

Pass

2♦

Pass

3♦

Pass

4♦

Pass

4♥

Pass

4♠

Pass

4NT

Pass

5♦(2)

Pass

6♦

All Pass

(1) 22+ total points(2) one or four key cards

West

North

East

South

Wbridge5

Jack

Wbridge5

Jack

-

-

Pass

2♦(1)

Pass

2NT(2)

Pass

3♦

Pass

4♣(3)

Pass

4♥

Pass

4♠

Pass

4NT

Pass

5♣(4)

Pass

5♥(5)

Pass

5♠(6)

Pass

7♦(7)

All Pass

(1) Strong one-suiter.(2) Positive, less than 2 spades, 3+ length in the other suits.(3) Agreed diamonds as trump, 10-12 support points.(4) One or four key cards.(5) Do you have the trump queen?(6) No.(7) I really didn't need the trump queen as partner has 3+ trumps, at
most one spade and the heart ace.

Jack found the lay-down grand, while Wbridge5 didn't explore further over 5♦.
11 Imps to Jack

Jack was not as successful in at least two other deals from the finals.
On two deals Jack bid 3NT and 6NT, without a stopper in the opponents' bid
suit. On the 3NT mishap, going down, at the other table Wbridge5 did well to made
4♥. On the 6NTx mishap Wbridge5 made 6♣,
and won 19 Imps, more than the difference
in the match.

SummarySome statistical snapshots

The average swing-per-board (spb):For the round robin: the
average spb for all matches = 4.75
For the round robin: the average spb for matches between top four finishers
(Jack, Shark Bridge, Wbridge5 and Micro Bridge) = 4.3
For the semifinal matches (Wbridge5 vs. Shark Bridge, Jack vs. Micro Bridge):
the average spb = 4.08
For the final match (Wbridge5 vs. Jack): the average spb = 4.86
For the top-four from the round robin and the semifinal and final matches: the
average spb = 4.32, *Norm=4.25* For the 2007 Bermuda Bowl/Venice Cup/Senior
Bowl/Transnational Teams, the combined spb = 4.25

While this is very limited data, the results point to lower Imp swings per
board and less high swing occurrences when 'more evenly matched-higher ranked'
robots are playing, with the results approaching those for high level human
play.

Wbridge5 and Jack performed best, and based
on recent performances, appear to be at the top of robotic play. While Wbridge5
successfully defended its championship with its excellent play, Jack outscored Wbridge5 in their
head-to-head matches (32 boards in the round robin and 64 boards in the final)
237-216. Considering the robots aren't influenced by the
importance of a board or the conditions under which a board or match is played,
overall, Jack
performed better than Wbridge5. Wbridge5 performed better when it counted
most, which for robots is a random event. Along with Wbridge5 and Jack,
Shark Bridge performed admirably, winning the Individual, finishing second in
the round robin, and putting up a good match against Wbridge5 in the semifinals.

Randomness clearly plays a role in the short-term outcome.
For a best estimate of relative strength, 1,000+ board matches would be
informative. The World Computer-Bridge Championships, similar to human
championships, aren't meant to determine who is best, only to crown a champion
after much play. Not withstanding, recent performances are a strong
indication of the robots' relative strength.