initial commit

.gitignore

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+/stockfish/

engine.py

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+import chess
+import chess.engine
+import random
+import eval
+
+
+def main():
+    fools_mate = "rnbqkbnr/pppp1ppp/4p3/8/5PP1/8/PPPPP2P/RNBQKBNR b KQkq f3 0 2"
+    board = chess.Board(fools_mate)
+    print(board, '\n')
+    moves = {}
+    for i in range(10):
+        move = pick_move(board)
+        if move is None:
+            break
+
+        simulate_game(board, move, 100)
+        moves[move] = board
+        board = chess.Board(fools_mate)
+
+    analyze_results(moves)
+
+
+def analyze_results(moves: dict):
+    for m, b in moves.items():
+        manual_score = eval.score_game(b)
+        engine_score = eval.analyze_with_stockfish(b)
+        print(f"score for move {m}: manual_score={manual_score}, engine_score={engine_score}")
+
+
+def pick_move(board: chess.Board) -> chess.Move | None:
+    """
+    Pick a random move
+    :param board: chess board
+    :return: a valid move or None if no valid move available
+    """
+    if len(list(board.legal_moves)) == 0:
+        return None
+    return random.choice(list(board.legal_moves))
+
+
+def simulate_game(board: chess.Board, move: chess.Move, depth: int):
+    """
+    Simulate a game starting with the given move
+    :param board: chess board
+    :param move: chosen move
+    :param depth: number of moves that should be simulated after playing the chosen move
+    :return: the score for the simulated game
+    """
+    engine = chess.engine.SimpleEngine.popen_uci("./stockfish/stockfish-ubuntu-x86-64-avx2")
+    board.push(move)
+    print(move)
+    print(board, '\n')
+    for i in range(depth):
+        if board.is_game_over():
+            engine.quit()
+            return
+        r = engine.play(board, chess.engine.Limit(depth=2))
+        print(r)
+        board.push(r.move)
+        print(board, '\n')
+
+    engine.quit()
+
+
+if __name__ == '__main__':
+    main()

eval.py

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+import chess
+import chess.engine
+
+# Eval constants for scoring chess boards
+# Evaluation metric inspired by Tomasz Michniewski: https://www.chessprogramming.org/Simplified_Evaluation_Function
+
+PIECE_VALUES = {
+    chess.PAWN: 100,
+    chess.KNIGHT: 320,
+    chess.BISHOP: 330,
+    chess.ROOK: 500,
+    chess.QUEEN: 900,
+    chess.KING: 20000
+}
+
+pawn_eval = [
+    0, 0, 0, 0, 0, 0, 0, 0,
+    5, 10, 10, -20, -20, 10, 10, 5,
+    5, -5, -10, 0, 0, -10, -5, 5,
+    0, 0, 0, 20, 20, 0, 0, 0,
+    5, 5, 10, 25, 25, 10, 5, 5,
+    10, 10, 20, 30, 30, 20, 10, 10,
+    50, 50, 50, 50, 50, 50, 50, 50,
+    0, 0, 0, 0, 0, 0, 0, 0
+]
+knight_eval = [
+    -50, -40, -30, -30, -30, -30, -40, -50,
+    -40, -20, 0, 0, 0, 0, -20, -40,
+    -30, 0, 10, 15, 15, 10, 0, -30,
+    -30, 5, 15, 20, 20, 15, 5, -30,
+    -30, 0, 15, 20, 20, 15, 0, -30,
+    -30, 5, 10, 15, 15, 10, 5, -30,
+    -40, -20, 0, 5, 5, 0, -20, -40,
+    -50, -40, -30, -30, -30, -30, -40, -50
+]
+bishop_eval = [
+    -20, -10, -10, -10, -10, -10, -10, -20,
+    -10, 5, 0, 0, 0, 0, 5, -10,
+    -10, 10, 10, 10, 10, 10, 10, -10,
+    -10, 0, 10, 10, 10, 10, 0, -10,
+    -10, 5, 5, 10, 10, 5, 5, -10,
+    -10, 0, 5, 10, 10, 5, 0, -10,
+    -10, 0, 0, 0, 0, 0, 0, -10,
+    -20, -10, -10, -10, -10, -10, -10, -20
+]
+rook_eval = [
+    0, 0, 0, 5, 5, 0, 0, 0,
+    -5, 0, 0, 0, 0, 0, 0, -5,
+    -5, 0, 0, 0, 0, 0, 0, -5,
+    -5, 0, 0, 0, 0, 0, 0, -5,
+    -5, 0, 0, 0, 0, 0, 0, -5,
+    -5, 0, 0, 0, 0, 0, 0, -5,
+    5, 10, 10, 10, 10, 10, 10, 5,
+    0, 0, 0, 0, 0, 0, 0, 0
+]
+queen_eval = [
+    -20, -10, -10, -5, -5, -10, -10, -20,
+    -10, 0, 0, 0, 0, 0, 0, -10,
+    -10, 0, 5, 5, 5, 5, 0, -10,
+    -5, 0, 5, 5, 5, 5, 0, -5,
+    0, 0, 5, 5, 5, 5, 0, -5,
+    -10, 5, 5, 5, 5, 5, 0, -10,
+    -10, 0, 5, 0, 0, 0, 0, -10,
+    -20, -10, -10, -5, -5, -10, -10, -20
+]
+king_eval = [
+    20, 30, 10, 0, 0, 10, 30, 20,
+    20, 20, 0, 0, 0, 0, 20, 20,
+    -10, -20, -20, -20, -20, -20, -20, -10,
+    20, -30, -30, -40, -40, -30, -30, -20,
+    -30, -40, -40, -50, -50, -40, -40, -30,
+    -30, -40, -40, -50, -50, -40, -40, -30,
+    -30, -40, -40, -50, -50, -40, -40, -30,
+    -30, -40, -40, -50, -50, -40, -40, -30
+]
+
+PIECE_TABLES = {
+    chess.WHITE: {
+        chess.PAWN: pawn_eval,
+        chess.KNIGHT: knight_eval,
+        chess.BISHOP: bishop_eval,
+        chess.ROOK: rook_eval,
+        chess.QUEEN: queen_eval,
+        chess.KING: king_eval
+    },
+    chess.BLACK: {
+        chess.PAWN: list(reversed(pawn_eval)),
+        chess.KNIGHT: list(reversed(knight_eval)),
+        chess.BISHOP: list(reversed(bishop_eval)),
+        chess.ROOK: list(reversed(rook_eval)),
+        chess.QUEEN: list(reversed(queen_eval)),
+        chess.KING: list(reversed(king_eval))
+    }
+}
+
+
+def score_game(board: chess.Board) -> float:
+    """
+    Calculate the score of the given board regarding the given color
+    :param board: the chess board
+    :return: score metric
+    """
+    outcome = board.outcome()
+    if outcome is not None:
+        if outcome.termination == chess.Termination.CHECKMATE:
+            return float('inf') if outcome.winner == chess.WHITE else float('-inf')
+        else:  # draw
+            return 0
+
+    score = 0
+    for s in chess.SQUARES:
+        piece = board.piece_at(s)
+        if piece is None:
+            continue
+
+        if piece.color == chess.WHITE:
+            score += PIECE_VALUES[piece.piece_type] * PIECE_TABLES[chess.WHITE][piece.piece_type][s]
+        else:
+            score -= PIECE_VALUES[piece.piece_type] * PIECE_TABLES[chess.BLACK][piece.piece_type][s]
+
+    return score
+
+
+def analyze_with_stockfish(board: chess.Board) -> chess.engine.PovScore:
+    """
+    Calculate the score of the given board using stockfish
+    :param board:
+    :return:
+    """
+    engine = chess.engine.SimpleEngine.popen_uci("./stockfish/stockfish-ubuntu-x86-64-avx2")
+    info = engine.analyse(board, chess.engine.Limit(depth=20))
+    engine.quit()
+    return info["score"]

requirements.txt

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+chess==1.10.0