Refine pattern detection and add an advanced chess NNUE that can train for 20 epoch.

```
import chess
import chess.pgn
import chess.engine

class ChessEngine:
    def __init__(self, stockfish_path="stockfish"):
        self.board = chess.Board()
        self.engine = chess.engine.SimpleEngine.popen_uci(stockfish_path)
        self.piece_values = {
            chess.PAWN: 100,
            chess.KNIGHT: 320,
            chess.BISHOP: 330,
            chess.ROOK: 500,
            chess.QUEEN: 900,
            chess.KING: 20000
        }
        self.killer_moves = {}
        self.history_heuristic = {}
        self.transposition_table = {}
        self.max_depth = 64

    def hash_board(self):
        return self.board.transposition_key()

    def evaluate_position(self):
        """
        Enhanced evaluation function that includes superpositional evaluation and tactical patterns.
        """
        if self.board.is_checkmate():
            return -float('inf') if self.board.turn else float('inf')
        if self.board.is_stalemate() or self.board.is_insufficient_material():
            return 0

        score = self.material_evaluation()
        score += self.superpositional_evaluation()

        return score

    def material_evaluation(self):
        """
        Basic material evaluation based on piece values.
        """
        score = 0
        for square in chess.SQUARES:
            piece = self.board.piece_at(square)
            if piece:
                value = self.piece_values[piece.piece_type]
                score += value if piece.color == chess.WHITE else -value
        return score

    def superpositional_evaluation(self):
        """
        Advanced positional evaluation that includes king safety, pawn structure, and piece coordination.
        Dynamically changes based on the game's phase (opening, middlegame, endgame).
        """
        score = 0

        # King safety evaluation
        score += self.evaluate_king_safety()

        # Pawn structure evaluation
        score += self.evaluate_pawn_structure()

        # Piece coordination
        score += self.evaluate_piece_coordination()

        # Adjust dynamically based on game phase
        score += self.dynamic_phase_adjustment()

        return score

    def evaluate_king_safety(self):
        """
        Evaluate king safety based on pawn shield and enemy threats.
        """
        score = 0
        # Example logic for evaluating king safety
        if self.board.king(chess.WHITE):
            white_king_square = self.board.king(chess.WHITE)
            score += self.king_safety_penalty(white_king_square, chess.WHITE)
        if self.board.king(chess.BLACK):
            black_king_square = self.board.king(chess.BLACK)
            score -= self.king_safety_penalty(black_king_square, chess.BLACK)

        return score

    def king_safety_penalty(self, king_square, color):
        """
        Penalize unsafe king positions based on pawn coverage and enemy piece proximity.
        """
        penalty = 0
        pawn_shield_squares = list(chess.SquareSet(chess.BB_PAWN_ATTACKS[color][king_square]))
        for square in pawn_shield_squares:
            if not self.board.piece_at(square):
                penalty -= 20  # Penalize missing pawns near the king
        return penalty

    def evaluate_pawn_structure(self):
        """
        Evaluate the strength and weaknesses in the pawn structure.
        """
        score = 0
        # Check for doubled pawns, isolated pawns, passed pawns, etc.
        score += self.pawn_structure_bonus(chess.WHITE)
        score -= self.pawn_structure_bonus(chess.BLACK)
        return score

    def pawn_structure_bonus(self, color):
        """
        Analyze pawn structure for a given color.
        """
        bonus = 0
        pawns = self.board.pieces(chess.PAWN, color)
        for pawn in pawns:
            # Passed pawn bonus
            if self.is_passed_pawn(pawn, color):
                bonus += 50

            # Penalize doubled pawns
            if self.is_doubled_pawn(pawn, color):
                bonus -= 20

            # Penalize isolated pawns
            if self.is_isolated_pawn(pawn, color):
                bonus -= 30

        return bonus

    def is_passed_pawn(self, pawn_square, color):
        """
        Checks if a pawn is a passed pawn (no opposing pawns in front of it).
        """
        if color == chess.WHITE:
            for sq in chess.SQUARES[pawn_square + 8:]:
                if self.board.piece_at(sq) and self.board.piece_at(sq).piece_type == chess.PAWN and self.board.piece_at(sq).color == chess.BLACK:
                    return False
        else:
            for sq in chess.SQUARES[:pawn_square - 8]:
                if self.board.piece_at(sq) and self.board.piece_at(sq).piece_type == chess.PAWN and self.board.piece_at(sq).color == chess.WHITE:
                    return False
        return True

    def is_doubled_pawn(self, pawn_square, color):
        """
        Checks if a pawn is doubled (another pawn of the same color on the same file).
        """
        file = chess.square_file(pawn_square)
        return len([sq for sq in chess.SQUARES if chess.square_file(sq) == file and self.board.piece_at(sq) and self.board.piece_at(sq).color == color]) > 1

    def is_isolated_pawn(self, pawn_square, color):
        """
        Checks if a pawn is isolated (no friendly pawns on adjacent files).
        """
        file = chess.square_file(pawn_square)
        adjacent_files = [file - 1, file + 1]
        for f in adjacent_files:
            if any(self.board.piece_at(chess.square(f, rank)) and self.board.piece_at(chess.square(f, rank)).piece_type == chess.PAWN for rank in range(8)):
                return False
        return True

    def evaluate_piece_coordination(self):
        """
        Evaluates the coordination between pieces (e.g., rooks on open files, knights in the center).
        """
        score = 0
        # Example: bonus for rooks on open files
        score += self.rooks_on_open_files_bonus(chess.WHITE)
        score -= self.rooks_on_open_files_bonus(chess.BLACK)

        # Example: bonus for knights in central squares
        score += self.knights_in_center_bonus(chess.WHITE)
        score -= self.knights_in_center_bonus(chess.BLACK)

        return score

    def rooks_on_open_files_bonus(self, color):
        """
        Bonus for rooks on open files (files without pawns).
        """
        bonus = 0
        rooks = self.board.pieces(chess.ROOK, color)
        for rook in rooks:
            if self.is_open_file(chess.square_file(rook)):
                bonus += 50
        return bonus

    def is_open_file(self, file):
        """
        Checks if a file is open (no pawns of either color).
        """
        return all(self.board.piece_at(chess.square(file, rank)) is None or self.board.piece_at(chess.square(file, rank)).piece_type != chess.PAWN for rank in range(8))

    def knights_in_center_bonus(self, color):
        """
        Bonus for knights controlling central squares.
        """
        bonus = 0
        knights = self.board.pieces(chess.KNIGHT, color)
        central_squares = [chess.D4, chess.D5, chess.E4, chess.E5]
        for knight in knights:
            if knight in central_squares:
                bonus += 30
        return bonus

    def dynamic_phase_adjustment(self):
        """
        Adjust the evaluation score based on the current phase of the game.
        """
        phase = self.get_game_phase()
        if phase == "opening":
            return 20  # Example adjustment for opening
        elif phase == "middlegame":
            return 50  # Midgame usually involves more dynamic play
        elif phase == "endgame":
            return 100  # Endgames favor simpler evaluations like passed pawns
        return 0

    def get_game_phase(self):
        """
        Determines the current phase of the game (opening, middlegame, or endgame).
        """
        num_pieces = len(list(self.board.piece_map()))
        if num_pieces > 25:
            return "opening"
        elif num_pieces > 10:
            return "middlegame"
        else:
            return "endgame"

    def tactical_pattern_recognition(self, move):
        """
        Recognizes tactical patterns such as forks, pins, skewers, and discovered attacks.
        """
        score = 0

        # Detect forks
        if self.is_fork(move):
            score += 100

        # Detect pins
        if self.is_pin(move):
            score += 80

        # Detect skewers
        if self.is_skewer(move):
            score += 80

        # Detect discovered attacks
        if self.is_discovered_attack(move):
            score += 90

        return score

    def is_fork(self, move):
        """
        Detects if a move results in a fork (attacks two or more valuable pieces).
        """
        attacker = self.board.piece_at(move.from_square)
        if attacker and attacker.piece_type in [chess.KNIGHT, chess.QUEEN]:
            attacked_squares = list(self.board.attacks(move.to_square))
            valuable_targets = [self.board.piece_at(sq) for sq in attacked_squares if self.board.piece_at(sq) and self.piece_values[self.board.piece_at(sq).piece_type] >= self.piece_values[chess.ROOK]]
            return len(valuable_targets) >= 2
        return False

    def is_pin(self, move):
        """
        Detects if a move results in a pin (a piece is immobilized due to a more valuable piece behind it).
        """
        attacker = self.board.piece_at(move.from_square)
        if attacker and attacker.piece_type in [chess.BISHOP, chess.ROOK, chess.QUEEN]:
            attacked_squares = list(self.board.attacks(move.to_square))
            for sq in attacked_squares:
                piece = self.board.piece_at(sq)
                if piece and piece.color != attacker.color and piece.piece_type == chess.KING:
                    return True
        return False

    def is_skewer(self, move):
        """
        Detects if a move results in a skewer (a valuable piece is forced to move, exposing a less valuable piece behind it).
        """
        attacker = self.board.piece_at(move.from_square)
        if attacker and attacker.piece_type in [chess.BISHOP, chess.ROOK, chess.QUEEN]:
            attacked_squares = list(self.board.attacks(move.to_square))
            for sq in attacked_squares:
                piece = self.board.piece_at(sq)
                if piece and piece.color != attacker.color and self.piece_values[piece.piece_type] >= self.piece_values[chess.ROOK]:
                    return True
        return False

    def is_discovered_attack(self, move):
        """
        Detects if a move results in a discovered attack (a move opens up an attack by a hidden piece).
        """
        piece = self.board.piece_at(move.from_square)
        if piece and piece.piece_type in [chess.PAWN, chess.KNIGHT]:
            for direction in [chess.BB_RANK_ATTACKS, chess.BB_FILE_ATTACKS, chess.BB_DIAGONAL_ATTACKS]:
                if piece in direction:
                    return True
        return False

    def load_pgn(self, file_path):
        with open(file_path, 'r') as pgn_file:
            game = chess.pgn.read_game(pgn_file)
            while game:
                board = game.board()
                for move in game.mainline_moves():
                    board.push(move)
                    self.board = board
                    self.get_best_move(4)
                game = chess.pgn.read_game(pgn_file)

    def stop_engine(self):
        self.engine.quit()

# Example usage
if __name__ == "__main__":
    engine = ChessEngine()
    engine.load_pgn("example_game.pgn")
    engine.stop_engine()