Safe Haskell | None |
---|---|
Language | Haskell2010 |
AUTHOR
- Dr. Alistair Ward
DESCRIPTION
- Quantifies the fitness of a game.
- By measuring the fitness from the perspective of the player who just moved (rather than the next player to move), an automated player can test various moves & select the fittest.
- maximumDefended :: NPieces
- measurePieceSquareValue :: (Enum x, Enum y, Num pieceSquareValue, Ord x, Ord y) => PieceSquareArray x y pieceSquareValue -> Game x y -> pieceSquareValue
- measurePieceSquareValueIncrementally :: (Enum x, Enum y, Num pieceSquareValue, Ord x, Ord y) => pieceSquareValue -> PieceSquareArray x y pieceSquareValue -> Game x y -> pieceSquareValue
- measureValueOfMaterial :: (Fractional criterionValue, Fractional rankValue, Ord criterionValue, Real rankValue) => RankValues rankValue -> Game x y -> CriterionValue criterionValue
- measureValueOfCastlingPotential :: (Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue
- measureValueOfDefence :: (Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue
- measureValueOfDoubledPawns :: (Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue
- measureValueOfIsolatedPawns :: (Enum x, Fractional criterionValue, Ord criterionValue, Ord x) => Game x y -> CriterionValue criterionValue
- measureValueOfPassedPawns :: forall x y criterionValue. (Enum y, Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue
- evaluateFitness :: (Enum x, Enum y, Fractional criterionValue, Fractional pieceSquareValue, Fractional rankValue, Fractional weightedMean, Ord x, Ord y, Real criterionValue, Real criterionWeight, Real pieceSquareValue, Real rankValue, Show x, Show y) => Maybe pieceSquareValue -> Game x y -> Reader criterionWeight pieceSquareValue rankValue x y (WeightedMeanAndCriterionValues weightedMean criterionValue)
Constants
maximumDefended :: NPieces Source #
- The constant maximum total number of times the pieces of either side, can be defended.
- This calculation assumes that:
every piece can defend another in every direction it can attack,
which is impossible, since in a 2-D board one can always draw a perimeter around the pieces, beyond which there're zero pieces to defend, so the outer pieces can never be fully utilised;
all
Pawn
s have been queened, which is unrealistic.
Functions
measurePieceSquareValue :: (Enum x, Enum y, Num pieceSquareValue, Ord x, Ord y) => PieceSquareArray x y pieceSquareValue -> Game x y -> pieceSquareValue Source #
Measures the piece-square value from the perspective of the last player to move.
measurePieceSquareValueIncrementally Source #
:: (Enum x, Enum y, Num pieceSquareValue, Ord x, Ord y) | |
=> pieceSquareValue | The value before the last move was applied, & therefore also from the perspective of the previous player. |
-> PieceSquareArray x y pieceSquareValue | |
-> Game x y | |
-> pieceSquareValue |
- Measures the piece-square value from the perspective of the last player to move.
- The previous value is provided, to enable calculation by difference.
- N.B.: because of diminishing returns, the piece-square value for everything but quiet moves is calculated from scratch.
measureValueOfMaterial :: (Fractional criterionValue, Fractional rankValue, Ord criterionValue, Real rankValue) => RankValues rankValue -> Game x y -> CriterionValue criterionValue Source #
Measure the arithmetic difference between the total rank-value of the pieces currently held by either side; https://chessprogramming.wikispaces.com/Material.
measureValueOfCastlingPotential :: (Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue Source #
Measure the arithmetic difference between the potential to Castle, on either side.
measureValueOfDefence :: (Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue Source #
- Measure the normalised arithmetic difference between the number of pieces defending each of one's own, on either side.
- N.B. the rank-value of the defended piece is irrelevant because; it's the unknown value of the attacker that counts, since that's what the defender has the opportunity to counter-strike.
- N.B. defence of the
King
is irrelevent, because it can't be taken. - N.B. it's the total number of defenders which is relevant, rather than whether each piece has some protection, since it's the individual battles but the war which counts.
- CAVEAT: this criterion competes with mobility, since each defended piece blocks the path of the defender.
measureValueOfDoubledPawns :: (Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue Source #
- Measure the arithmetic difference between the number of doubled
Pawn
s on either side; https://chessprogramming.wikispaces.com/Doubled+Pawn. - N.B.: measures tripled
Pawn
s as equivalent to two doubledPawn
s. - CAVEAT: this is a negative attribute, so the weighted normalised value shouldn't exceed the reduction due to
measureValueOfMaterial
resulting from aPawn
-sacrifice.
measureValueOfIsolatedPawns :: (Enum x, Fractional criterionValue, Ord criterionValue, Ord x) => Game x y -> CriterionValue criterionValue Source #
- Measure the arithmetic difference between the number of isolated
Pawn
s on either side; https://chessprogramming.wikispaces.com/Isolated+Pawn. - CAVEAT: this is a negative attribute, so the weighted normalised value shouldn't exceed the reduction due to
measureValueOfMaterial
resulting from aPawn
-sacrifice.
measureValueOfPassedPawns :: forall x y criterionValue. (Enum y, Fractional criterionValue, Ord criterionValue) => Game x y -> CriterionValue criterionValue Source #
Measure the arithmetic difference between the number of passed Pawn
s on either side; https://chessprogramming.wikispaces.com/Passed+Pawn.
:: (Enum x, Enum y, Fractional criterionValue, Fractional pieceSquareValue, Fractional rankValue, Fractional weightedMean, Ord x, Ord y, Real criterionValue, Real criterionWeight, Real pieceSquareValue, Real rankValue, Show x, Show y) | |
=> Maybe pieceSquareValue | An optional value for the specified game. |
-> Game x y | |
-> Reader criterionWeight pieceSquareValue rankValue x y (WeightedMeanAndCriterionValues weightedMean criterionValue) |
- Evaluates the fitness of the board from the perspective of the last player to move. If the game has ended, the fitness is maximum for checkmate or zero for a draw, but otherwise is the weighted mean of various criteria; https://chessprogramming.wikispaces.com/Evaluation.
- Also returns the break-down of those criterion-values with a non-zero criterion-weight.
- Besides measuring the difference between the total rank-value on either side,
other criteria are selected to represent known attributes of a good position,
but which won't be pay dividends any time soon, & therefore won't be represented by
measureValueOfMaterial
within the limited future predicted. - Many possible criteria aren't measured because they're, either currently or soon, represented by those that are, typically
measureValueOfMaterial
.