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https://github.com/tiyn/yeschess.git
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engine: added piece-square tables
Piece square tables are a way to encurage the engine to put pieces on active squares. Each piece got a corresponding table.
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TiynGER
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@ -39,3 +39,6 @@ Due to easier off the board checking a
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The engine uses a simple implementation of the
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[NegaMax](https://www.chessprogramming.org/NegaMax)-algorithm.
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For the evaluation function each piece has a corresponding value.
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Additionally there are [piece-square tables](https://www.chessprogramming.org/Piece-Square_Tables)
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to encurage putting pieces on active squares.
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@ -36,10 +36,10 @@ type
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b: int # `b` describes the amount of bishops.
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r: int # `r` describes the amount of rooks.
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q: int # `q` describes the amount of queens.
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Pieces = array[10,int]
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Pieces = array[10, int]
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const
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Block = 999 ## \
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Block = 999 ## \
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## `Block` is the value assigned to empty blocked fields in a board.
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WPawn* = 1
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## `WPawn` is the value assigned to a square in a board with a white pawn.
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@ -54,9 +54,9 @@ const
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WQueen* = 5 ## \
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## `WQueen` is the value assigned to a square in a board with a white
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## queen.
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WKing = 6 ## \
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WKing* = 6 ## \
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## `WKing` is the value assigned to a square in a board with a white king.
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WEnPassant = 7 ## \
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WEnPassant = 7 ## \
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## `WEnPassant` is assigned to a square in a board with an invisible white
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## en passant pawn.
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BPawn* = -WPawn ## \
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@ -71,9 +71,9 @@ const
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## `BRook` is the value assigned to a square in a board with a black rook.
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BQueen* = -WQueen ## \
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## `BQueen` is the value assigned to a square in a board with a black queen.
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BKing = -WKing ## \
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BKing* = -WKing ## \
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## `BKing` is the value assigned to a square in a board with a black king.
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BEnPassant = -WEnPassant ## \
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BEnPassant = -WEnPassant ## \
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## `BEnPassant` is assigned to a square in a board with an invisible black
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## en passant pawn.
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N = 10 ## `N` describes a move a field up the board from whites perspective.
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@ -205,7 +205,8 @@ proc moveToNotation*(move: Move): string =
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res.add(dest)
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var color = move.color
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var prom = PieceChar[move.prom]
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if (color == Color.White and dest[1] == '8') or (color == Color.Black and dest[1] == '1'):
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if (color == Color.White and dest[1] == '8') or (color == Color.Black and
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dest[1] == '1'):
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res.add(prom)
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return res
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@ -812,8 +813,8 @@ proc threeMoveRep(chess: Chess): bool =
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var lastCastleRights = chess.previousCastleRights[chess.previousBoard.high]
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var reps = 0
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for stateInd in (chess.previousBoard.low)..(chess.previousBoard.high):
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if (chess.previousBoard[stateInd] == lastState and chess.previousCastleRights[
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stateInd] == lastCastleRights):
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if (chess.previousBoard[stateInd] == lastState and
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chess.previousCastleRights[stateInd] == lastCastleRights):
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reps = reps + 1
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return reps >= 3
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@ -837,10 +838,12 @@ proc checkInsufficientMaterial(board: Board): bool =
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index = piece - WPawn # map lowest value to 0
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pieces[index] += 1
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elif piece <= BPawn and piece >= BRook:
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index = WRook - piece # map black pieces after whites
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index = WRook - piece # map black pieces after whites
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pieces[index] += 1
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let wpieces: PieceAmount = (pieces[0], pieces[1], pieces[2], pieces[3], pieces[4])
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let bpieces: PieceAmount = (pieces[5], pieces[6], pieces[7], pieces[8], pieces[9])
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let wpieces: PieceAmount = (pieces[0], pieces[1], pieces[2], pieces[3],
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pieces[4])
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let bpieces: PieceAmount = (pieces[5], pieces[6], pieces[7], pieces[8],
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pieces[9])
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return (wpieces in InsufficientMaterial) and (bpieces in InsufficientMaterial)
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proc isStalemate*(chess: Chess, color: Color): bool =
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125
src/engine.nim
125
src/engine.nim
@ -1,47 +1,147 @@
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import algorithm
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import ./chess.nim
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type
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MoveTree* = object
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MoveTree = object
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## `Movetree` is a visualization for possible moves.
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chess*: Chess
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chess: Chess
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evaluation: float
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children*: seq[Movetree]
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children: seq[Movetree]
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const
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PawnVal = 1 ## `PawnVal` is the engines value for a pawn.
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KnightVal = 3 ## `KnightVal` is the engines value for a knight.
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BishopVal = 3 ## `BishopVal` is the engines value for a bishop.
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RookVal = 5 ## `RookVal` is the engines value for a rook.
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QueenVal = 9 ## `QueenVal` is the engines value for a queen.
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CheckmateVal = -1000 ## `CheckmateVal` is the engines value for a checkmate.
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PawnVal = 10 ## `PawnVal` is the engines value for a pawn.
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KnightVal = 31 ## `KnightVal` is the engines value for a knight.
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BishopVal = 33 ## `BishopVal` is the engines value for a bishop.
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RookVal = 50 ## `RookVal` is the engines value for a rook.
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QueenVal = 90 ## `QueenVal` is the engines value for a queen.
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CheckmateVal = -10000 ## `CheckmateVal` is the engines value for a checkmate.
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DrawVal = 0 ## `DrawVal` is the engines value for a draw.
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LoVal = -1000000 ## `LoVal` is a value always lower than any evaluation.
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pawnTable = [
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 5, 10, 10, -20, -20, 10, 10, 5, 0,
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0, 5, -5, -10, 0, 0, -10, -5, 5, 0,
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0, 0, 0, 0, 20, 20, 0, 0, 0, 0,
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0, 5, 5, 10, 25, 25, 10, 5, 5, 0,
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0, 10, 10, 20, 30, 30, 20, 10, 10, 0,
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0, 50, 50, 50, 50, 50, 50, 50, 50, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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] ## `pawnTable` is the piece-square table for pawns.
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knightTable = [
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, -50, -40, -30, -30, -30, -30, -40, -50, 0,
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0, -40, -20, 0, 5, 5, 0, -20, -40, 0,
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0, -30, 0, 10, 15, 15, 10, 0, -30, 0,
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0, -30, 5, 15, 20, 20, 15, 5, -30, 0,
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0, -30, 0, 15, 20, 20, 15, 0, -30, 0,
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0, -30, 5, 10, 15, 15, 10, 5, -30, 0,
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0, -40, -20, 0, 0, 0, 0, -20, -40, 0,
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0, -50, -40, -30, -30, -30, -30, -40, -50, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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] ## `knightTable` is the piece-square table for pawns.
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bishopTable = [
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, -20, -10, -10, -10, -10, -10, -10, -20, 0,
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0, -10, 5, 0, 0, 0, 0, 5, -10, 0,
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0, -10, 10, 10, 10, 10, 10, 10, -10, 0,
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0, -10, 0, 10, 10, 10, 10, 0, -10, 0,
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0, -10, 5, 5, 10, 10, 5, 5, -10, 0,
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0, -10, 0, 5, 10, 10, 5, 0, -10, 0,
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0, -10, 0, 0, 0, 0, 0, 0, -10, 0,
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0, -20, -10, -10, -10, -10, -10, -10, -20, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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] ## `bishopTable` is the piece-square table for pawns.
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rookTable = [
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 5, 5, 0, 0, 0, 0,
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0, -5, 0, 0, 0, 0, 0, 0, -5, 0,
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0, -5, 0, 0, 0, 0, 0, 0, -5, 0,
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0, -5, 0, 0, 0, 0, 0, 0, -5, 0,
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0, -5, 0, 0, 0, 0, 0, 0, -5, 0,
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0, -5, 0, 0, 0, 0, 0, 0, -5, 0,
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0, 5, 10, 10, 10, 10, 10, 10, 5, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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] ## `rookTable` is the piece-square table for pawns.
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queenTable = [
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, -20, -10, -10, -5, -5, -10, -10, -20, 0,
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0, -10, 0, 0, 0, 0, 5, 0, -10, 0,
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0, -10, 0, 5, 5, 5, 5, 0, -10, 0,
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0, -10, 0, 5, 5, 5, 5, 0, -10, 0,
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0, -10, 0, 5, 5, 5, 5, 0, -10, 0,
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0, -10, 0, 5, 5, 5, 5, 0, -10, 0,
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0, -10, 0, 0, 0, 0, 0, 0, -10, 0,
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0, -20, -10, -10, -5, -5, -10, -10, -20, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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] ## `queenTable` is the piece-square table for pawns.
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kingTable = [
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 20, 30, 10, 0, 0, 10, 30, 20, 0,
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0, 20, 20, 0, 0, 0, 0, 20, 20, 0,
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0, -10, -20, -20, -20, -20, -20, -20, -10, 0,
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0, -20, -30, -30, -40, -40, -30, -30, -20, 0,
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0, -30, -40, -40, -50, -50, -40, -40, -30, 0,
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0, -30, -40, -40, -50, -50, -40, -40, -30, 0,
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0, -30, -40, -40, -50, -50, -40, -40, -30, 0,
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0, -30, -40, -40, -50, -50, -40, -40, -30, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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] ## `kingTable` is the piece-square table for pawns.
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proc pieceEval(chess: Chess): int =
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## Returns the evaluation of existing pieces on the `board`
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var evaluation = DrawVal
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for square in chess.board:
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for ind, square in chess.board:
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case square:
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of WPawn:
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evaluation += ord(Color.White) * PawnVal
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evaluation += ord(Color.White) * pawnTable[ind]
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of WKnight:
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evaluation += ord(Color.White) * KnightVal
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evaluation += ord(Color.White) * knightTable[ind]
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of WBishop:
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evaluation += ord(Color.White) * BishopVal
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evaluation += ord(Color.White) * bishopTable[ind]
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of WRook:
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evaluation += ord(Color.White) * RookVal
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evaluation += ord(Color.White) * rookTable[ind]
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of WQueen:
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evaluation += ord(Color.White) * QueenVal
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evaluation += ord(Color.White) * queenTable[ind]
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of WKing:
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evaluation += ord(Color.White) * kingTable[ind]
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of BPawn:
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evaluation += ord(Color.Black) * PawnVal
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evaluation += ord(Color.Black) * pawnTable.reversed[ind]
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of BKnight:
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evaluation += ord(Color.Black) * KnightVal
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evaluation += ord(Color.Black) * knightTable.reversed[ind]
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of BBishop:
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evaluation += ord(Color.Black) * BishopVal
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evaluation += ord(Color.Black) * bishopTable.reversed[ind]
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of BRook:
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evaluation += ord(Color.Black) * RookVal
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evaluation += ord(Color.Black) * rookTable.reversed[ind]
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of BQueen:
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evaluation += ord(Color.Black) * QueenVal
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evaluation += ord(Color.Black) * queenTable.reversed[ind]
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of BKing:
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evaluation += ord(Color.White) * kingTable.reversed[ind]
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else:
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continue
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return evaluation
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@ -67,7 +167,8 @@ proc spanMoveTree(chess: Chess, depth: int): MoveTree =
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## Create and return a Movetree of a given `chess` with a given maximum `depth`.
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var mTree: MoveTree
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mTree.chess = chess
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if depth != 0 and not chess.isCheckmate(chess.toMove) and not chess.isStalemate(chess.toMove):
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if depth != 0 and not chess.isCheckmate(chess.toMove) and
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not chess.isStalemate(chess.toMove):
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let possibleMoves = chess.genLegalMoves(chess.toMove)
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for move in possibleMoves:
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var tmpChess = chess
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@ -97,7 +198,7 @@ proc bestMove*(chess: Chess, depth: int): Move =
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tmpChess.checkedMove(move)
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var tmpMTree = tmpChess.spanMoveTree(depth)
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var tmpEval = -tmpMTree.negaMax()
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echo("move:", moveToNotation(move),"; eval:", tmpEval)
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echo("move:", moveToNotation(move), "; eval:", tmpEval)
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if tmpEval > bestEval:
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bestEval = tmpEval
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bestMove = move
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@ -86,7 +86,8 @@ testSuite ChessTest of TestSuite:
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], Color.Black)
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var testBestMove = self.chess.bestMove(2)
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self.check(testBestMove.start != 0)
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self.check(indToField(testBestMove.start) != "g5" or indToField(testBestMove.dest) != "f4")
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self.check(indToField(testBestMove.start) != "g5" or indToField(
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testBestMove.dest) != "f4")
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method testBestMoveTacticWhite() =
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self.chess = initChess([
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@ -101,7 +102,8 @@ testSuite ChessTest of TestSuite:
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], Color.White)
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var testBestMove = self.chess.bestMove(2)
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self.check(testBestMove.start != 0)
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self.check(indToField(testBestMove.start) != "g4" or indToField(testBestMove.dest) != "f5")
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self.check(indToField(testBestMove.start) != "g4" or indToField(
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testBestMove.dest) != "f5")
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when isMainModule:
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@ -8,10 +8,10 @@ import ./engine.nim
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let berserk = pyImport("berserk")
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var session = berserk.TokenSession(secret.api_token)
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var client = berserk.Client(session=session)
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var client = berserk.Client(session = session)
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let engineID = "tiyn-ychess"
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let engineDifficulty = 2
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let engineDifficulty = 3
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let toAccept = ["tiynger"]
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