20-add-negamax-eval-function (#31)

Reviewed-on: #31
Co-authored-by: Josh <josh@joshuaschuett.com>
Co-committed-by: Josh <josh@joshuaschuett.com>

scripts/simulation.py

@@ -0,0 +1,182 @@
+import uuid
+from binding.python_c_ffi import Board
+from binding.python_c_ffi import Move
+from binding.python_c_ffi import ChessFFI
+from binding.python_c_ffi import WHITE
+from binding.python_c_ffi import print_board
+from binding.python_c_ffi import sq_to_coord
+from scripts.evaluation import RandomEval
+from scripts.evaluation import NegaMaxEval
+from scripts.format import LongPGNFormatter
+
+
+YMD_HM = "%Y-%m-%d-%H-%M"
+MAX_MOVES = 256
+DATA_PATH = "./data/games"
+
+
+class Engine:
+    def __init__(self, strat_white=None, strat_black=None, max_plys=500):
+        self.chess_ffi = ChessFFI()
+        self.board = Board()
+        self.max_plys = max_plys
+        self.moves = []
+        self.fens = []
+        self._load_attack_cache()
+        self._seed_engine()
+
+        random_strat = RandomEval(chess_ffi=self.chess_ffi)
+
+        if not strat_white:
+            self.strat_white = random_strat
+        else:
+            self.strat_white = strat_white
+
+        if not strat_black:
+            self.strat_black = random_strat
+        else:
+            self.strat_black = strat_black
+
+        self.strategies = {
+            "white": {
+                "name": self.strat_white.NAME,
+                "params": self.strat_white.get_params()
+            },
+            "black": {
+                "name": self.strat_black.NAME,
+                "params": self.strat_black.get_params()
+            },
+        }
+
+
+    def run(self, fen, save=True):
+        self.chess_ffi.load_fen(self.board, fen)
+        self._clear_moves()
+        plys = 0
+
+        self.fens.append(fen)
+        while plys <= self.max_plys:
+            print_board(self.board)
+
+            moves_buf = (Move * MAX_MOVES)()
+            n_legal = self.chess_ffi.get_legal_moves(self.board, moves_buf)
+
+            game_over, result = self._is_game_over(n_legal)
+            if game_over:
+                print(result)
+                break
+
+            legal = [moves_buf[i] for i in range(n_legal)]
+            if self.board.side_to_move == WHITE:
+                best_move = self.strat_white.get_best_move(self.board, legal)
+            else:
+                best_move = self.strat_black.get_best_move(self.board, legal)
+
+            new_board = Board()
+            if not self.chess_ffi.apply_move_on_copy(self.board, new_board, best_move):
+                print("ERROR: apply_move_on_copy failed")
+                break
+
+            self.board = new_board
+            plys += 1
+
+            fen_string = self.chess_ffi.board_to_fen(self.board)
+            self.fens.append(fen_string)
+            
+            move = self.to_uci(best_move)
+            self.moves.append(move)
+
+            if self.board.halfmove_clock >= 100:
+                print("draw (50-move rule)")
+                result = "1/2-1/2"
+                break
+
+        print("done")
+        print(len(self.moves))
+
+        if save:
+            print("saving game to disk.")
+            id = uuid.uuid4().hex
+
+            formatter = LongPGNFormatter(
+                save_path=DATA_PATH,
+                strategies=self.strategies,
+                result=result
+            )
+            formatter.save_game(id, self.moves, self.fens)
+
+
+    def side_tag(self, side):
+        return 'w' if side == WHITE else 'b'
+
+
+    def load_fen(self, fen):
+        self.chess_ffi.load_fen(self.board, fen)
+
+
+    def to_uci(self, move):
+        fr = sq_to_coord(getattr(move, "from"))
+        to = sq_to_coord(move.to)
+
+        # Only add a promotion letter if promo is set
+        promo_letter = ""
+        promo_val = int(getattr(move, "promo", 0) or 0)
+        if promo_val:
+            # Normalize piece id to type 0..5 (P,N,B,R,Q,K)
+            pt = promo_val % 6
+            # Map N=1, B=2, R=3, Q=4
+            letter_map = {1: "n", 2: "b", 3: "r", 4: "q"}
+            promo_letter = letter_map.get(pt, "")
+
+        return f"{fr}{to}{promo_letter}"
+
+
+    def _load_attack_cache(self):
+        self.chess_ffi.init_attack_cache()
+
+
+    def _clear_moves(self):
+        self.moves = []
+
+
+    def _seed_engine(self):
+        import ctypes as C, time
+
+        seed = time.time_ns()
+        s32 = int(seed) & 0xFFFFFFFF
+
+        libc = C.CDLL("libc.so.6")   # on Ubuntu
+        libc.srand.argtypes = (C.c_uint,)
+        libc.srand.restype  = None
+        libc.srand(C.c_uint(s32))
+        return s32
+
+
+    def _is_game_over(self, legal_moves):
+        if legal_moves == 0:
+            if self.chess_ffi.in_check(self.board, self.board.side_to_move):
+                # Checkmate.
+                if self.board.side_to_move == WHITE:
+                    result = "0-1"
+                else:
+                    result = "1-0"
+            else:
+                # Stalemate.
+                result = "1/2-1/2"
+            return True, result
+        return False, None
+    
+
+if __name__ == "__main__":
+    chess_ffi = ChessFFI()
+    nega_strat_1 = NegaMaxEval(chess_ffi=chess_ffi, depth=2, cp_window=5)
+    nega_strat_2 = NegaMaxEval(chess_ffi=chess_ffi, depth=1, cp_window=5)
+
+
+    engine = Engine(
+        strat_white=nega_strat_1,
+        strat_black=nega_strat_2,
+    )
+
+    fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
+    engine.run(fen, save=True)