BishBosh.ContextualNotation.PositionHashQualifiedMoveTree

AUTHOR

Dr. Alistair Ward

DESCRIPTION

Facilitates matching of the current position in a tree built from standard openings.

Types

Type-synonyms

type TryToMatchMoves = Bool

Whether to attempt to exactly match moves with a standard opening; transpositions won't be matched.

type TryToMatchViaJoiningMove = Bool

Whether to attempt to join the current position to a standard opening that's only one ply away.

type TryToMatchColourFlippedPosition = Bool

Whether to attempt to match a colour-flipped version of the current position with a standard opening

type PreferVictories = Bool

Whether from all matching positions extracted from the tree, to prefer moves which result in a greater probability of victory, for the player who has the next move.

type MatchSwitches = (TryToMatchMoves, TryToMatchViaJoiningMove, TryToMatchColourFlippedPosition)

The switches used to control attempts to find a match amongst standard openings.

Data-types

data NodeLabel positionHash

Each label of the tree contains a Zobrist-hash of the current position, augmented (except in the case of the apex-game) by the last move that was played, & any conclusive result.

data PositionHashQualifiedMoveTree positionHash

Constructor.

Functions

findNextOnymousQualifiedMovesForPosition :: Bits positionHash => FindMatch positionHash

• For all matching positions, return the subsequent qualifiedMove.
• By matching the position rather than the precise sequence of moves, transpositions https://www.chessprogramming.org/Transposition can also be identified.
• N.B.: a comparison between the number of pieces in the game we're required to match & the decreasing number of pieces down the tree, permits early termination of the search.
• CAVEAT: a null list can result from either match-failure, or a match with the final move of a game.

findNextOnymousQualifiedMoves :: Bits positionHash => MatchSwitches -> FindMatch positionHash

• Calls findNextOnymousQualifiedMovesForGame to find an exact match for the current game in the tree.
• Calls findNextOnymousQualifiedMovesForPosition to find a match for the current position in the tree.
• On failure, it searches the tree to find a match for the colour-flipped position.
• On failure, it searches for any move which can be used to join the position with the tree.
• On failure, it searches for any move which can be used to join the colour-flipped position with the tree.
• CAVEAT: the order of these searches has been hard-coded.

maybeRandomlySelectOnymousQualifiedMove :: (Bits positionHash, RandomGen randomGen) => randomGen -> PreferVictories -> MatchSwitches -> PositionHashQualifiedMoveTree positionHash -> Game -> Maybe (QualifiedMove, [Name])

Randomly select a qualifiedMove from matching positions in the tree, & supply the names of those archived games from which it originated.

Constructors

fromQualifiedMoveForest

Arguments

:: Bits positionHash

=> Bool

IncrementalEvaluation.

-> Zobrist positionHash

-> QualifiedMoveForest

-> PositionHashQualifiedMoveTree positionHash

Constructor: augment the specified qualified-move forest with a Zobrist-hash of the position & include the default initial game at the apex.

Predicates

isTerminal :: PositionHashQualifiedMoveTree positionHash -> Bool

Predicate.