def value(game_state: Othello, depth, heuristic, alpha=-1, beta=1):
"""
Get value for game_state according to alpha beta pruning
:param game_state: The state to evaluate
:param depth: do alpha beta pruning until this depth is reached
:param heuristic: Function reference for the heuristic used to score game state after maximum search depth is reached
:param alpha: value of alpha
:param beta: value of beta
:return: value of move
Compare https://github.com/karlstroetmann/Artificial-Intelligence/blob/master/SetlX/game-alpha-beta.stlx
"""
if game_state.game_is_over():
return game_state.utility(game_state.get_current_player())
if depth == 0:
# return heuristic of game state
return heuristic(game_state.get_current_player(), game_state)
val = alpha
for move in game_state.get_available_moves():
next_state = game_state.deepcopy()
next_state.play_position(move)
val = max({
val, -1 * AlphaBetaPruning.value(next_state, depth - 1,
heuristic, -beta, -alpha)
})
if val >= beta:
return val
alpha = max({val, alpha})
return val
def get_move(self, game_state: Othello):
"""
Will select the best move according to the value of the resulting game_state according to monte carlo
:param game_state: current game state
:return: best move in available moves
"""
# Use start library if it is selected and still included
if self._use_start_lib and game_state.get_turn_nr(
) < 21: # check whether start move match
moves = self._start_tables.get_available_moves_of_start_tables(
game_state)
if len(moves) > 0:
return util.translate_move_to_pair(moves[random.randrange(
len(moves))])
# According to experience the number of moves to consider decreases relevantly after reaching a certain
# turn number. Therefore it is possible to increase the search depth without loosing to much time.
# We dynamically increase the search depth after reaching turn_number 40
search_depth = self._search_depth
turn_number = game_state.get_turn_nr()
if turn_number > 40:
search_depth += turn_number // 10
# Dict used to store a list of the moves resulting in a state with the respective value
best_moves = dict()
# Evaluate each available move
for move in game_state.get_available_moves():
# Play the move to get the resulting state
next_state = game_state.deepcopy()
next_state.play_position(move)
# Evaluate the state using the selected function
if self._use_monte_carlo:
result = -AlphaBetaPruning.value_monte_carlo(
next_state,
search_depth - 1,
self._heuristic,
mc_count=self._mc_count)
else:
result = -AlphaBetaPruning.value(
next_state, self._search_depth - 1, self._heuristic)
# Append the move to the list of states with that value
if result not in best_moves.keys():
best_moves[result] = []
best_moves[result].append(move)
# Determine the best result
best_result = max(best_moves.keys())
if self._use_monte_carlo:
print(AlphaBetaPruning.value_monte_carlo.cache_info())
AlphaBetaPruning.value_monte_carlo.cache_clear()
else:
print(AlphaBetaPruning.value.cache_info())
AlphaBetaPruning.value.cache_clear()
# Play one random move with the best possible result
return best_moves[best_result][random.randrange(
len(best_moves[best_result]))]
def value_monte_carlo(game_state: Othello,
depth,
heuristic,
alpha=-1,
beta=1,
mc_count=100):
"""
get score for alpha beta pruning
:param game_state: actual game state
:param depth: do alpha beta pruning this depth
:param heuristic: score game state after alpha beta pruning with this heuristic
:param mc_count: number of games which are played in each terminal node after alpha beta pruning
:param alpha: value of alpha
:param beta: value of beta
:return: score of move
Compare https://github.com/karlstroetmann/Artificial-Intelligence/blob/master/SetlX/game-alpha-beta.stlx
"""
if game_state.game_is_over():
return game_state.utility(game_state.get_current_player())
if depth == 0:
# use monte carlo player if enabled
# mc_count = number of played games
mc = MonteCarlo(big_number=mc_count,
use_start_libs=False,
preprocessor_n=-1,
heuristic=heuristic,
use_multiprocessing=True)
# get best move
move = mc.get_move(game_state)
# return winnings stats of best move
prob = mc.get_move_probability(move)
return prob
val = alpha
for move in game_state.get_available_moves():
next_state = game_state.deepcopy()
next_state.play_position(move)
val = max({
val, -1 * AlphaBetaPruning.value_monte_carlo(next_state,
depth - 1,
heuristic,
-beta,
-alpha,
mc_count=mc_count)
})
if val >= beta:
return val
alpha = max({val, alpha})
return val
