This software is tricky to write correctly, and it is hard to verify correctness.

• EVAL: evaluates a bridge hand and, optionally, produces a playing tree
  This program determines whether one side can take the specified number of tricks against perfect defense and, if so, exactly how it can be done. Newer versions have dramatically improved performance.
• PLAY: uses the playing tree to play optimally
  You get to play defense against the program's perfect offense. In this manner, you will observe how any possible defense can be overcome.

• The Version 1 system uses alpha-beta search, including some amenities: dynamic rank equivalence, suit ordering, and dynamic rank ordering. A brief discussion of some implementation details is available.

• The Version 2 system uses node isomorphism and is an order of magnitude faster than Version 1. It also allows the user to configure memory usage. This version was a bit trickier to code since now there is a DAG (directed acyclic graph) rather than merely a tree.

• The Version 3 system uses node equivalence. For difficult problems it is an order of magnitude faster than Version 2. Version 3 files are fundamentally different from and incompatible with earlier versions.

• The Version 4 system uses dynamic backtracking, some dynamic heuristics that are enhanced by learning techniques utilizing self-organizing lists, and some code tuning. Version 4 appears to be about twice as fast as Version 3. (For some hard hands, it is an order of magnitude faster than Version 3 for tree construction.) Optionally, the program determines the maximum number of tricks that are guaranteed makable, as opposed to just deciding the question for a specified number of tricks.

• Can you solve this devilish hand, which was described in rec.games.bridge? If not, EVAL can solve it for you.
• Here is another hand.
• This slam hand was presented as the Bridge Plaza Deal of the Week in April 1997.

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