Robotics Reference
In-Depth Information
In the bidding stage
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the players make bids,
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as in an auction, for
the right to determine how many
tricks
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need to be made by each side
and to choose which suit is trumps
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. Once the bidding has ended,
which happens when three successive players say “pass” or “no bid”, the
play of the cards begins.
How Computers Play the Cards in Bridge
It is generally recognised amongst strong Bridge players that the play of
the cards is easier than the bidding. Of the relatively small number of
Bridge programs that have been written to date, most rely on some sort
of planning for the play of the cards. The 1997 World Computer Bridge
Champion program, Bridge Baron, employed a form of planning called
Hierarchical Task Network planning. This form of planning is analagous
to the goal
→
subgoal approach used by Newell, Shaw and Simon in
their General Problem Solver program GPS,
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planning the solution to
a problem by repeatedly breaking down tasks within the problem into
smaller and smaller sub-tasks, until all of the sub-tasks can be carried
out successfully. The level of play achieved by this approach in Bridge
has been anything but specacular, prompting many-times World Bridge
Champion Bob Hamman to say of the best Bridge programs of the mid-
1990s that “They would have to improve to be hopeless.” [5]
In a 1989 conference paper provocatively entitled “The Million
Pound Bridge Program” I proposed a different approach, using a tech-
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There are two principal goals for each of the partnerships during the bidding stage. Firstly,
each
bid
is designed to convey information to the bidder's partner about the cards in the bidder's
hand. There are various bidding systems and conventions that have been developed to aid this
process, analagous to special purposes languages in which coded messages may be used. A second
main goal of the bidding is for the partners to agree on how many
tricks
they will try to make. As
in a traditional auction, the bidding process continues until no player wishes to make a higher bid,
whereupon the highest bid determines the number of tricks to be made and the trump suit (if any).
This final bid is called the
contract
.
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Most bids consist of two parts, for example “one diamond” or “two spades” or “three no-
trumps”. The number part of a bid indicates how many tricks in excess of six the partnership
will try to make, with the
trump
suit being whatever suit is named in the second part of the bid.
(Trump cards take precedence over other cards when determining which side has won the trick.)
So a bid of “one diamond” means that the partnership will try to make at least seven tricks with
diamonds as trumps; a bid of “two spades” means trying to make at least eight tricks with spades as
trumps; and a bid of “three no-trumps” means trying to make at least nine tricks when there is no
trump suit.
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A trick consists of four cards, one played from each of North, South, East and West.
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A card in the trump suit supercedes all cards in the other tree suits.
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See the section “The General Problem Solver” in Chapter 6.
