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Cleaned up the implementation of minimax and alphabeta. Added one mor…
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…e test. Trigger CI
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@miselico
miselico committed Nov 14, 2023
1 parent dabf4be commit d525cd0
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Showing 4 changed files with 130 additions and 89 deletions.
39 changes: 22 additions & 17 deletions src/schnapsen/bots/alphabeta.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@
GamePlayEngine,
SchnapsenTrickScorer,
)
from .minimax import OneFixedMoveBot


class AlphaBetaBot(Bot):
"""
Expand All @@ -35,16 +35,13 @@ def __init__(self) -> None:
super().__init__()

def get_move(self, perspective: PlayerPerspective, leader_move: Optional[Move]) -> Move:
assert (
perspective.get_phase() == GamePhase.TWO
), "AlphaBetaBot can only work in the second phase of the game."
assert (perspective.get_phase() == GamePhase.TWO), "AlphaBetaBot can only work in the second phase of the game."
_, move = self.value(
perspective.get_state_in_phase_two(),
perspective.get_engine(),
leader_move=leader_move,
maximizing=True,
)
assert move
return move

def value(
Expand All @@ -55,7 +52,7 @@ def value(
maximizing: bool,
alpha: float = float("-inf"),
beta: float = float("inf"),
) -> tuple[float, Optional[Move]]:
) -> tuple[float, Move]:
my_perspective: PlayerPerspective
if leader_move is None:
# we are the leader
Expand All @@ -70,7 +67,7 @@ def value(
leader: Bot
follower: Bot
if leader_move is None:
# we are leader,
# we are leader, call self to get the follower to play
value, _ = self.value(
state=state,
engine=engine,
Expand All @@ -80,20 +77,16 @@ def value(
beta=beta,
)
else:
# We are the follower.
# We are the follower. We need to complete the trick and then call self to play the next trick, with the correct maximizing, depending on who is the new leader
leader = OneFixedMoveBot(leader_move)
follower = OneFixedMoveBot(move)
new_game_state, rounds = engine.play_at_most_n_tricks(
game_state=state, new_leader=leader, new_follower=follower, n=1
)
assert rounds == 1
new_game_state = engine.play_one_trick(game_state=state, new_leader=leader, new_follower=follower)
winning_info = SchnapsenTrickScorer().declare_winner(new_game_state)
if winning_info:
winner = winning_info[0].implementation
points = winning_info[1]
follower_wins = winner == follower
if not follower_wins:
assert winner == leader

if not follower_wins:
points = -points
if not maximizing:
Expand All @@ -104,12 +97,13 @@ def value(
leader_stayed = leader == new_game_state.leader.implementation

if leader_stayed:
# At the next step, the leader is our opponent, and it will be doing the opposite of what we do.
next_maximizing = not maximizing
else: # if not leader_stayed
# At the next step we will have become the leader, so we will keep doing what we did
next_maximizing = maximizing
value, _ = self.value(
new_game_state, engine, None, next_maximizing, alpha, beta
)
# implementation note: the previous two case could be written with a xor, but this seemed more readable
value, _ = self.value(new_game_state, engine, None, next_maximizing, alpha, beta)
if maximizing:
if value > best_value:
best_move = move
Expand All @@ -124,5 +118,16 @@ def value(
beta = min(beta, best_value) # alphabeta pruning
if beta <= alpha:
break
assert best_move # We are sure the best_move can no longer be None. We assert to make sure we did not make a logical mistake
return best_value, best_move


class OneFixedMoveBot(Bot):
def __init__(self, move: Move) -> None:
self.first_move: Optional[Move] = move

def get_move(self, perspective: PlayerPerspective, leader_move: Optional[Move]) -> Move:
assert self.first_move, "This bot can only play one move, after that it ends"
move = self.first_move
self.first_move = None
return move
16 changes: 6 additions & 10 deletions src/schnapsen/bots/minimax.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
SchnapsenTrickScorer,
)


class MiniMaxBot(Bot):
"""
A bot playing the minimax strategy in the second phase of the game.
Expand Down Expand Up @@ -39,7 +40,6 @@ def get_move(self, perspective: PlayerPerspective, leader_move: Optional[Move])
leader_move=leader_move,
maximizing=True,
)
assert move
return move

def value(
Expand All @@ -48,7 +48,7 @@ def value(
engine: GamePlayEngine,
leader_move: Optional[Move],
maximizing: bool,
) -> tuple[float, Optional[Move]]:
) -> tuple[float, Move]:
"""Get the score and the corresponding move which eithers maxmizes or minimizes the objective.
Args:
Expand All @@ -74,7 +74,7 @@ def value(
leader: Bot
follower: Bot
if leader_move is None:
# call self to get the follower to play
# we are leader, call self to get the follower to play
value, _ = self.value(
state=state,
engine=engine,
Expand All @@ -85,17 +85,13 @@ def value(
# We are the follower. We need to complete the trick and then call self to play the next trick, with the correct maximizing, depending on who is the new leader
leader = OneFixedMoveBot(leader_move)
follower = OneFixedMoveBot(move)
new_game_state, rounds = engine.play_at_most_n_tricks(
game_state=state, new_leader=leader, new_follower=follower, n=1
)
assert rounds == 1
new_game_state = engine.play_one_trick(game_state=state, new_leader=leader, new_follower=follower)
winning_info = SchnapsenTrickScorer().declare_winner(new_game_state)
if winning_info:
winner = winning_info[0].implementation
points = winning_info[1]
follower_wins = winner == follower
if not follower_wins:
assert winner == leader

if not follower_wins:
points = -points
if not maximizing:
Expand All @@ -119,6 +115,7 @@ def value(
elif not maximizing and value < best_value:
best_move = move
best_value = value
assert best_move # We are sure the best_move can no longer be None. We assert to make sure we did not make a logical mistake
return best_value, best_move


Expand All @@ -131,4 +128,3 @@ def get_move(self, perspective: PlayerPerspective, leader_move: Optional[Move])
move = self.first_move
self.first_move = None
return move

52 changes: 52 additions & 0 deletions src/schnapsen/game.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1525,6 +1525,40 @@ def play_game(self, bot1: Bot, bot2: Bot, rng: Random) -> tuple[Bot, int, Score]
winner, points, score = self.play_game_from_state(game_state=game_state, leader_move=None)
return winner, points, score

def get_random_phase_two_state(self, rng: Random) -> GameState:
class RandBot(Bot):
def __init__(self, rand: Random, name: Optional[str] = None) -> None:
super().__init__(name)
self.rng = rand

def get_move(
self,
perspective: PlayerPerspective,
leader_move: Optional[Move],
) -> Move:
moves: list[Move] = perspective.valid_moves()
move = self.rng.choice(moves)
return move

while True:
cards = self.deck_generator.get_initial_deck()
shuffled = self.deck_generator.shuffle_deck(cards, rng)
hand1, hand2, talon = self.hand_generator.generateHands(shuffled)
leader_state = BotState(implementation=RandBot(rand=rng), hand=hand1)
follower_state = BotState(implementation=RandBot(rand=rng), hand=hand2)
game_state = GameState(
leader=leader_state,
follower=follower_state,
talon=talon,
previous=None
)
second_phase_state, _ = self.play_at_most_n_tricks(game_state, RandBot(rand=rng), RandBot(rand=rng), 5)
winner = self.trick_scorer.declare_winner(second_phase_state)
if winner:
continue
if second_phase_state.game_phase() == GamePhase.TWO:
return second_phase_state

def play_game_from_state_with_new_bots(self, game_state: GameState, new_leader: Bot, new_follower: Bot, leader_move: Optional[Move]) -> tuple[Bot, int, Score]:
"""
Continue a game which might have started before with other bots, with new bots.
Expand Down Expand Up @@ -1571,6 +1605,23 @@ def play_game_from_state(self, game_state: GameState, leader_move: Optional[Move

return winner.implementation, points, winner.score

def play_one_trick(self, game_state: GameState, new_leader: Bot, new_follower: Bot) -> GameState:
"""
Plays one tricks (including the one started by the leader, if provided) on a game which might have started before.
The new bots are new_leader and new_follower.
This method does not make changes to the provided game_state.
:param game_state: The state of the game to start from
:param new_leader: The bot which will take the leader role in the game.
:param new_follower: The bot which will take the follower in the game.
:returns: The GameState reached and the number of steps actually taken.
"""
state, rounds = self.play_at_most_n_tricks(game_state, new_leader, new_follower, 1)
assert rounds == 1
return state

def play_at_most_n_tricks(self, game_state: GameState, new_leader: Bot, new_follower: Bot, n: int) -> tuple[GameState, int]:
"""
Plays up to n tricks (including the one started by the leader, if provided) on a game which might have started before.
Expand All @@ -1582,6 +1633,7 @@ def play_at_most_n_tricks(self, game_state: GameState, new_leader: Bot, new_foll
:param game_state: The state of the game to start from
:param new_leader: The bot which will take the leader role in the game.
:param new_follower: The bot which will take the follower in the game.
:param n: the maximum number of tricks to play
:returns: The GameState reached and the number of steps actually taken.
"""
Expand Down
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