107 lines
2.7 KiB
Python
107 lines
2.7 KiB
Python
from sys import stderr
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import time
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import math
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from typing import Any, Callable
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import Goban
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def _next_color(color):
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return Goban.Board._BLACK if color == Goban.Board._WHITE else Goban.Board._WHITE
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# Returns heuristic, move
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def _alphabeta(
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board: Goban.Board,
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heuristic: Callable[[Goban.Board, Any], float],
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color,
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move,
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alpha=-math.inf,
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beta=math.inf,
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depth: int = 3,
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) -> tuple[float, Any]:
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wantMax = (board.next_player != color)
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if depth == 0 or board.is_game_over():
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return heuristic(board, color), move
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if wantMax:
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acc = -math.inf, None
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for move in board.generate_legal_moves():
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board.push(move)
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value = (
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_alphabeta(
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board,
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alpha=alpha,
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beta=beta,
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move=move,
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heuristic=heuristic,
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color=_next_color(color),
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depth=depth - 1,
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)[0],
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move,
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)
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acc = max(
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acc,
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value,
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key=lambda t: t[0],
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)
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board.pop()
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if acc[0] >= beta:
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break # beta cutoff
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alpha = max(alpha, value[0])
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else:
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acc = math.inf, None
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for move in board.generate_legal_moves():
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board.push(move)
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value = (
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_alphabeta(
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board,
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alpha=alpha,
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beta=beta,
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move=move,
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heuristic=heuristic,
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color=_next_color(color),
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depth=depth - 1,
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)[0],
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move,
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)
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acc = min(
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acc,
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value,
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key=lambda t: t[0],
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)
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board.pop()
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if acc[0] <= alpha:
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break # alpha cutoff
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beta = min(beta, value[0])
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return acc
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def alphabeta(
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board: Goban.Board,
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heuristic: Callable[[Goban.Board, Any], float],
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color,
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depth: int = 3,
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):
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_, move = _alphabeta(board, move=-1, heuristic=heuristic, color=color, depth=depth)
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return move
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def IDDFS(board: Goban.Board, heuristic, color, duration: float, maxdepth=42):
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st = time.time()
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depth = 1
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move = -1
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while time.time() - st < duration and depth <= maxdepth:
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print("depth:", depth, time.time() - st, file=stderr)
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move = _alphabeta(
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board, heuristic, color, move=-1, alpha=-10, beta=10, depth=depth
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)[1]
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depth += 1
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print(time.time() - st, duration, depth, file=stderr)
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return move
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