class Negascout(object):
def __init__(self, board, colour):
# we want to create a node
self.tt = TranspositionTable()
# only use this board to complete the search
# save memory
self.board = deepcopy(board)
# for alpha beta search -- instead of passing it into the function calls we can use this
self.alpha = -inf
self.beta = inf
# defines the colours of min and max
self.player = colour
self.opponent = Board.get_opp_piece_type(self.player)
# default depth
self.depth = inf
# default move ordering with iterative deepening
self.actions_evaluated = []
self.actions_leftover = []
# data structures for machine learning
self.eval_depth = 0
self.minimax_val = 0
self.policy_vector = []
# dictionary storing the available moves of the board
self.available_actions = {
constant.WHITE_PIECE: {},
constant.BLACK_PIECE: {}
}
# generate the actions for the start of the game
# self.generate_actions()
self.undo_effected = []
self.time_alloc = 0
self.time_rem = 0
self.time_start = 0
self.time_end = 0
self.total_time = 0
# load the evaluation function based on the colour of the player
if self.player == constant.WHITE_PIECE:
self.evaluation = Evaluation("./XML", "/white_weights")
else:
self.evaluation = Evaluation("./XML", "/black_weights")
'''
* Alpha Beta - Minimax Driver Function
'''
def itr_negascout(self):
colour = self.player
# clear the transposition table every time we make a new move -- this is to ensure that it doesn't grow too big
# if self.board.phase == constant.MOVING_PHASE and self.board.move_counter == 0:
if self.board.phase == constant.PLACEMENT_PHASE:
# clear the transposition table every time we want to evaluate a move in placement phase
# this is to limit the size of growth
self.tt.clear()
# set the max depth iterations based on the phase that we are in
MAX_ITER = 5
else:
MAX_ITER = 11
# update the root number of pieces every time we do a search on a new node
self.board.root_num_black = len(self.board.black_pieces)
self.board.root_num_white = len(self.board.white_pieces)
# default policy
available_actions = self.board.update_actions(colour)
action_set = set(available_actions)
if len(available_actions) == 0:
return None
if self.board.phase == constant.PLACEMENT_PHASE:
self.time_alloc = 1500
else:
self.time_alloc = 1200
# if we have reached 100 moves in the game and the game
if self.total_time > 90000 or self.board.move_counter > 120:
self.time_alloc = 500
# if we are near the final shrinking phase, then we can decrease the time it has to
# evaluate
if self.board.move_counter > 150:
self.time_alloc = 150
best_depth = 1
val, move = 0, None
best_move = None
self.time_rem = self.time_alloc
# iterative deepening begins here
for depth in range(1, MAX_ITER):
print(self.tt.size)
print(depth)
try:
self.time_start = self.curr_millisecond_time()
val, move = self.negascout(depth, -inf, inf, self.player)
# move = self.negascout(depth,self.player)
self.time_end = self.curr_millisecond_time()
self.time_rem = self.time_alloc - (self.time_end -
self.time_start)
print(move)
best_depth += 1
if move is not None and move in action_set:
best_move = move
except TimeOut:
print("TIMEOUT")
break
# add the time allocated to the total time
self.total_time += self.time_alloc
self.eval_depth = best_depth
return best_move
def set_player_colour(self, colour):
self.player = colour
self.opponent = Board.get_opp_piece_type(colour)
@staticmethod
def curr_millisecond_time():
return int(time() * 1000)
def negascout(self, depth, alpha, beta, colour):
# Timeout handling
self.time_end = self.curr_millisecond_time()
if self.time_end - self.time_start > self.time_rem:
raise TimeOut
opponent = Board.get_opp_piece_type(colour)
original_alpha = alpha
dic = {self.player: 1, self.opponent: -1}
move_to_try = None
# check if the current board state is in the transposition table
board_str = self.board.board_state.decode("utf-8")
key = self.tt.contains(board_str, colour, phase=self.board.phase)
if key is not None:
board_str = key[0]
entry = self.tt.get_entry(board_str, colour)
tt_value = entry[0]
tt_type = entry[1]
tt_best_move = entry[2]
tt_depth = entry[3]
# if we have found an entry in the transposition table, then the move
# we should try first is this best move
move_to_try = tt_best_move
#print(move_to_try)
#print("FOUND ENTRY IN TT")
if tt_depth >= depth:
if tt_type == constant.TT_EXACT:
#print("FOUND PV")
return tt_value, tt_best_move
elif tt_type == constant.TT_LOWER:
if tt_value > alpha:
#print("FOUND FAIL SOFT")
alpha = tt_value
elif tt_type == constant.TT_UPPER:
if tt_value < beta:
#print("FOUND FAIL HARD")
beta = tt_value
if alpha >= beta:
return tt_value, tt_best_move
actions = self.board.update_actions(colour)
# actions = actions_1
actions = self.board.sort_actions(actions, colour)
#actions = actions_1
# terminal test -- default case
if self.cutoff_test(depth):
val = self.evaluate_state(self.board, self.player,
actions) * dic[colour]
return val, None
# do the minimax search
best_val = -inf
best_action = None
if move_to_try is not None and move_to_try in actions:
#print("MOVE ORDERING")
# put the move to try at the first position -- therefore it will be searched first
actions = [move_to_try] + actions
i = 0
if len(actions) <= 12:
favourable = actions
elif 12 < len(actions) < 20:
favourable = actions[:12]
else:
favourable = actions[:len(actions) // 2]
# print(len(actions))
# start negascout here
for i, action in enumerate(favourable):
# skip over the best action in the tt table
if action == move_to_try and i > 0:
continue
elim = self.board.update_board(action, colour)
# if we are at the first node -- this is the best node we have found so far
# therefore we do a full search on this node
if i == 0:
# do a full search on the best move found so far
score, _ = self.negascout(depth - 1, -beta, -alpha, opponent)
score = -score
else:
# assume that the first move is the best move we have found so far,
# therefore to see if this is the case we can do a null window search on the
# rest of the moves, if the search breaks, then we know that the first move is
# the best move and it will return the best move
# but if the search "failed high" - i.e. the score is between alpha and beta
# we need to do a full research of the node to work out the minimax value
# do the null window search
score, _ = self.negascout(depth - 1, -alpha - 1, -alpha,
opponent)
score = -score
# if it failed high, then we just do a full search to find the actual best move
if alpha < score < beta:
score, _ = self.negascout(depth - 1, -beta, -score,
opponent)
score = -score
# get the best value and score
if best_val < score:
best_val = score
best_action = action
# reset alpha
if alpha < score:
alpha = score
# undo the action applied to the board -- we can now apply another move to the board
self.undo_actions(action, colour, elim)
# test for alpha beta cutoff
if alpha >= beta:
break
# store the values in the transposition table
if best_val <= original_alpha:
# then this is an upperbound -FAILHARD
tt_type = constant.TT_UPPER
elif best_val >= beta:
tt_type = constant.TT_LOWER
# print("LOWER")
else:
tt_type = constant.TT_EXACT
# print("EXACT")
# add the entry to the transposition table
self.tt.add_entry(self.board.board_state, colour, best_val, tt_type,
best_action, depth)
return best_val, best_action
def cutoff_test(self, depth):
if depth == 0:
return True
if self.is_terminal():
return True
return False
'''
* NEED TO THINK ABOUT IF THIS FUNCTION JUST EVALUATES THE NODES AT THE ROOT STATE DUE TO THE UNDO MOVES
-- NEED TO TEST THIS OUT SOMEHOW, because other than that the algorithm is working as intended
-- Need to work out some optimisations of the algorithm though
'''
def evaluate_state(self, board, colour, actions):
return self.evaluation.evaluate(board, colour, actions)
# update the available moves of the search algorithm after it has been instantiated
#
# def update_available_moves(self, node, available_moves):
# node.available_moves = available_moves
def update_board(self, board):
self.board = deepcopy(board)
def is_terminal(self):
return self.board.is_terminal()
def undo_actions(self, action, colour, elim):
return self.board.undo_action(action, colour, elim)
class Negamax(object):
def __init__(self, board, colour):
# we want to create a node
self.tt = TranspositionTable()
# only use this board to complete the search
# save memory
self.board = deepcopy(board)
# for alpha beta search -- instead of passing it into the function calls we can use this
self.alpha = -inf
self.beta = inf
# defines the colours of min and max
self.player = colour
self.opponent = Board.get_opp_piece_type(self.player)
# default depth
self.depth = inf
# default move ordering with iterative deepening
self.actions_evaluated = []
self.actions_leftover = []
# data structures for machine learning
self.eval_depth = 0
self.minimax_val = 0
self.policy_vector = []
# dictionary storing the available moves of the board
self.available_actions = {
constant.WHITE_PIECE: {},
constant.BLACK_PIECE: {}
}
# generate the actions for the start of the game
# self.generate_actions()
self.undo_effected = []
self.time_alloc = 0
self.time_rem = 0
self.time_start = 0
self.time_end = 0
self.evaluation = Evaluation("./XML", "/eval_weights")
'''
* Alpha Beta - Minimax Driver Function
'''
def itr_negamax(self):
# clear the transposition table every time we make a new move -- this is to ensure that it doesn't grow too big
if self.board.phase == constant.MOVING_PHASE and self.board.move_counter == 0:
#if self.board.phase == constant.PLACEMENT_PHASE:
self.tt.clear()
MAX_ITER = 10
# default policy
available_actions = self.board.update_actions(self.board, self.player)
# self.actions_leftover = self.board.update_actions(self.board, self.player)
if len(available_actions) == 0:
return None
#else:
# lets just set the default to the first move
# move = available_actions[0]
# time allocated per move in ms
'''
self.time_alloc = 0
if self.board.phase == constant.PLACEMENT_PHASE:
self.time_alloc = (30000 - self.time_alloc) / (24 - self.board.move_counter)
else:
self.time_alloc = (30000 - self.time_alloc) / (100 - self.board.move_counter)
'''
self.time_alloc = 5000
# get time
start_time = Negamax.curr_millisecond_time()
best_depth = 1
val, move = 0, None
# iterative deepening begins here
for depth in range(1, MAX_ITER):
print(self.tt.size)
print(depth)
try:
self.time_rem = self.time_alloc
self.time_start = self.curr_millisecond_time()
val, move = self.negamax(depth, -inf, inf, self.player)
self.time_end = self.curr_millisecond_time()
self.time_rem = self.time_alloc - (self.time_end -
self.time_start)
print(move)
best_depth += 1
except TimeOut:
print("TIMEOUT")
break
if Negamax.curr_millisecond_time() - start_time > self.time_alloc:
break
self.eval_depth = best_depth
return move
def set_player_colour(self, colour):
self.player = colour
self.opponent = Board.get_opp_piece_type(colour)
@staticmethod
def curr_millisecond_time():
return int(time() * 1000)
def negamax(self, depth, alpha, beta, colour):
# Timeout handling
self.time_end = self.curr_millisecond_time()
if self.time_end - self.time_start > self.time_rem:
raise TimeOut
opponent = Board.get_opp_piece_type(colour)
original_alpha = alpha
dic = {self.player: 1, self.opponent: -1}
'''
move_to_try = None
# check if the current board state is in the transposition table
board_str = self.board.board_state.decode("utf-8")
key = self.tt.contains(board_str,colour,phase=self.board.phase)
if key is not None:
board_str = key[0]
entry = self.tt.get_entry(board_str,colour)
tt_value = entry[0]
tt_type = entry[1]
tt_best_move = entry[2]
tt_depth = entry[3]
# if we have found an entry in the transposition table, then the move
# we should try first is this best move
move_to_try = tt_best_move
#print("FOUND ENTRY IN TT")
if tt_depth >= depth:
if tt_type == constant.TT_EXACT:
#print("FOUND PV")
return tt_value, tt_best_move
elif tt_type == constant.TT_LOWER:
if tt_value > alpha:
#print("FOUND FAIL SOFT")
alpha = tt_value
elif tt_type == constant.TT_UPPER:
if tt_value < beta:
#print("FOUND FAIL HARD")
beta = tt_value
if alpha >= beta:
return tt_value, None
'''
# terminal test -- default case
if self.cutoff_test(depth):
val = self.evaluate_state(self.board, self.player) #*dic[colour]
return val, None
# do the minimax search
best_val = -inf
best_action = None
actions = self.board.update_actions(self.board, colour)
'''
if move_to_try is not None and move_to_try in actions:
#print("MOVE ORDERING")
# put the move to try at the first position -- therefore it will be searched first
actions = [move_to_try] + actions
i = 0
'''
# get the favourable moves of the board
actions = self.get_favourable_actions(self.available_actions)
# if there are no favourable actions to iterate on - raise
if len(actions) < 0:
raise ReturnUnfavourableMove
for action in actions:
# skip over the best action in the tt table
'''
if action == move_to_try and i!= 0:
continue
i+=1
'''
self.board.update_board(action, colour)
score, temp = self.negamax(depth - 1, -beta, -alpha, opponent)
score = -score
if score > best_val:
best_val = score
best_action = action
if score > alpha:
alpha = score
self.undo_move()
if alpha >= beta:
break
'''
# store the values in the transposition table
if best_val <= original_alpha:
# then this is an upperbound -FAILHARD
tt_type = constant.TT_UPPER
elif best_val >= beta:
tt_type = constant.TT_LOWER
# print("LOWER")
else:
tt_type = constant.TT_EXACT
# print("EXACT")
'''
# add the entry to the transposition table
# self.tt.add_entry(self.board.board_state,colour,best_val,tt_type,best_action, depth)
return best_val, best_action
def cutoff_test(self, depth):
if depth == 0:
return True
if self.is_terminal():
return True
return False
'''
* NEED TO THINK ABOUT IF THIS FUNCTION JUST EVALUATES THE NODES AT THE ROOT STATE DUE TO THE UNDO MOVES
-- NEED TO TEST THIS OUT SOMEHOW, because other than that the algorithm is working as intended
-- Need to work out some optimisations of the algorithm though
'''
def evaluate_state(self, board, colour):
#return Evaluation.basic_policy(board,colour)
return self.evaluation.evaluate(board, self.player)
# update the available moves of the search algorithm after it has been instantiated
#
# def update_available_moves(self, node, available_moves):
# node.available_moves = available_moves
def update_board(self, board):
self.board = deepcopy(board)
def is_terminal(self):
return self.board.is_terminal()
def undo_move(self):
return self.board.undo_move()
class Negamax(object):
def __init__(self, board, colour):
# we want to create a node
self.tt = TranspositionTable()
# only use this board to complete the search
# save memory
self.board = deepcopy(board)
# for alpha beta search -- instead of passing it into the function calls we can use this
self.alpha = -inf
self.beta = inf
# defines the colours of min and max
self.player = colour
self.opponent = Board.get_opp_piece_type(self.player)
# default depth
self.depth = inf
# default move ordering with iterative deepening
self.actions_evaluated = []
self.actions_leftover = []
# data structures for machine learning
self.eval_depth = 0
self.minimax_val = 0
self.policy_vector = []
# dictionary storing the available moves of the board
self.available_actions = {
constant.WHITE_PIECE: {},
constant.BLACK_PIECE: {}
}
# generate the actions for the start of the game
# self.generate_actions()
self.undo_effected = []
self.time_alloc = 0
self.time_rem = 0
self.time_start = 0
self.time_end = 0
self.evaluation = Evaluation("./XML", "/eval_weights")
'''
* Alpha Beta - Minimax Driver Function
'''
def itr_negamax(self):
# clear the transposition table every time we make a new move -- this is to ensure that it doesn't grow too big
# if self.board.phase == constant.MOVING_PHASE and self.board.move_counter == 0:
#if self.board.phase == constant.PLACEMENT_PHASE:
self.tt.clear()
MAX_ITER = 10
# default policy
available_actions = self.board.update_actions(self.board, self.player)
print(len(available_actions))
action_set = set(available_actions)
# self.actions_leftover = self.board.update_actions(self.board, self.player)
if len(available_actions) == 0:
return None
#else:
# lets just set the default to the first move
# move = available_actions[0]
# time allocated per move in ms
'''
self.time_alloc = 0
if self.board.phase == constant.PLACEMENT_PHASE:
self.time_alloc = (30000 - self.time_alloc) / (24 - self.board.move_counter)
else:
self.time_alloc = (30000 - self.time_alloc) / (100 - self.board.move_counter)
'''
# self.time_alloc = 5000
# time allocated per move in ms
self.time_alloc = 0
total = 120000
if self.board.phase == constant.PLACEMENT_PHASE:
#self.time_alloc = (total/2 - self.time_alloc) / (24 - self.board.move_counter)
#total -= self.time_alloc
self.time_alloc = 1000
else:
#self.time_alloc = (total - self.time_alloc) / (100 - self.board.move_counter)
#total -= self.time_alloc
self.time_alloc = 1000
# get time
start_time = Negamax.curr_millisecond_time()
best_depth = 1
val, move = 0, None
# iterative deepening begins here
best_move = None
for depth in range(1, MAX_ITER):
print(self.tt.size)
print(depth)
try:
self.time_rem = self.time_alloc
self.time_start = self.curr_millisecond_time()
val, move = self.negamax(depth, -inf, inf, self.player)
self.time_end = self.curr_millisecond_time()
self.time_rem = self.time_alloc - (self.time_end -
self.time_start)
print(move)
best_depth += 1
# if we have a move that is not none lets always pick that move that is legal
# becuase we are doing a greedy search -- it sometimes returns an illegal move, not too sure why
# therefore here we check if a move is legal as well
if move is not None and move in action_set:
best_move = move
except TimeOut:
print("TIMEOUT")
break
if Negamax.curr_millisecond_time() - start_time > self.time_alloc:
break
self.eval_depth = best_depth
return best_move
def set_player_colour(self, colour):
self.player = colour
self.opponent = Board.get_opp_piece_type(colour)
@staticmethod
def curr_millisecond_time():
return int(time() * 1000)
# naive Negamax (depth limited) -- No Transposition Table
def negamax(self, depth, alpha, beta, colour):
# Timeout handling
self.time_end = self.curr_millisecond_time()
if self.time_end - self.time_start > self.time_rem:
raise TimeOut
opponent = Board.get_opp_piece_type(colour)
dic = {self.player: 1, self.opponent: -1}
# generate legal actions
actions_1 = self.board.update_actions(self.board, colour)
# print(len(actions))
actions = self.board.sort_actions(actions_1, colour)
# terminal test -- default case
if self.cutoff_test(depth):
val = self.evaluate_state(self.board, self.player,
actions) * dic[colour]
return val, None
# do the minimax search
best_val = -inf
best_action = None
# generate legal actions
#actions = self.board.update_actions(self.board, colour)
# split the actions into favourable an unfavourable
# if the length of actions is greater than X, then we can just choose to look through the first
# 5 'favourable' actions that we see right now
# if the length of actions is less than X, then we can just evaluate all possible actions we have
# THIS IS A GREEDY APPROACH TO MINIMAX THAT LIMITS OUR BRANCHING FACTOR OF THE GAME
if len(actions) > 8:
favourable = actions[:8]
else:
favourable = actions
# got here
#print("got here")
# depth reduction
R = 2
#print(favourable)
#self.board.print_board()
for action in favourable:
self.board.update_board(action, colour)
if action in favourable:
score, temp = self.negamax(depth - 1, -beta, -alpha, opponent)
else:
score, temp = self.negamax(depth - 1 - R, -beta, -alpha,
opponent)
score = -score
if score > best_val:
best_val = score
best_action = action
if score > alpha:
alpha = score
self.undo_move()
if alpha >= beta:
break
return best_val, best_action
def cutoff_test(self, depth):
if depth == 0:
return True
if self.is_terminal():
return True
return False
'''
* NEED TO THINK ABOUT IF THIS FUNCTION JUST EVALUATES THE NODES AT THE ROOT STATE DUE TO THE UNDO MOVES
-- NEED TO TEST THIS OUT SOMEHOW, because other than that the algorithm is working as intended
-- Need to work out some optimisations of the algorithm though
'''
def evaluate_state(self, board, colour, actions):
#return Evaluation.basic_policy(board,colour)
return self.evaluation.evaluate(board, colour, actions)
# update the available moves of the search algorithm after it has been instantiated
#
# def update_available_moves(self, node, available_moves):
# node.available_moves = available_moves
def update_board(self, board):
self.board = deepcopy(board)
def is_terminal(self):
return self.board.is_terminal()
def undo_move(self):
return self.board.undo_move()
class Negamax(object):
def __init__(self, board, colour, file_name):
# we want to create a node
self.tt = TranspositionTable()
# only use this board to complete the search
# save memory
self.board = deepcopy(board)
# for alpha beta search -- instead of passing it into the function calls we can use this
self.alpha = -inf
self.beta = inf
# defines the colours of min and max
self.player = colour
self.opponent = Board.get_opp_piece_type(self.player)
# default depth
self.depth = inf
# data structures for machine learning
self.eval_depth = 0
self.minimax_val = 0
self.policy_vector = []
# dictionary storing the available moves of the board
self.available_actions = {
constant.WHITE_PIECE: {},
constant.BLACK_PIECE: {}
}
# timing attributes
self.undo_effected = []
self.time_alloc = 0
self.time_rem = 0
self.time_start = 0
self.time_end = 0
self.total_time = 0
# load the evaluation function based on the colour of the player
if self.player == constant.WHITE_PIECE:
self.evaluation = Evaluation("./XML", "/white_weights")
else:
self.evaluation = Evaluation("./XML", "/black_weights")
'''
Iterative Deepening Negamax
This implements a time-cutoff such that search is terminated once we have reached the allocated time for evaluation.
IT RETURNS THE BEST MOVE IT HAS FOUND IN THE TIME ALLOCATED
'''
def itr_negamax(self):
# clear the transposition table every time we make a new move -- this is to ensure that it doesn't grow too big
# if self.board.phase == constant.MOVING_PHASE and self.board.move_counter == 0:
if self.board.phase == constant.PLACEMENT_PHASE:
# clear the transposition table every time we want to evaluate a move in placement phase
# this is to limit the size of growth
self.tt.clear()
# set the max depth iterations based on the phase that we are in
MAX_ITER = 5
else:
MAX_ITER = 11
# update the root number of pieces every time we do a search on a new node
self.board.root_num_black = len(self.board.black_pieces)
self.board.root_num_white = len(self.board.white_pieces)
# default policy
available_actions = self.board.update_actions(self.player)
# if there are no available actions to make, therefore we just return None -- this is a forfeit
if len(available_actions) == 0:
return None
if self.board.phase == constant.PLACEMENT_PHASE:
self.time_alloc = 1500
else:
self.time_alloc = 1200
# if we have reached 100 moves in the game and the game
if self.total_time > 90000 or self.board.move_counter > 120:
self.time_alloc = 500
# if we are near the final shrinking phase, then we can decrease the time it has to
# evaluate
if self.board.move_counter > 150:
self.time_alloc = 190
best_depth = 1
val, move = 0, None
# set the time remaining for each move evaluation
self.time_rem = self.time_alloc
# iterative deepening begins here
for depth in range(1, MAX_ITER):
# get the best move until cut off is reached
try:
self.time_start = self.curr_millisecond_time()
val, move = self.negamax(depth, -inf, inf, self.player)
self.time_end = self.curr_millisecond_time()
# update the time remaining
self.time_rem = self.time_alloc - (self.time_end -
self.time_start)
best_depth += 1
except TimeOut:
break
# add the total time to the time allocated
self.total_time += self.time_alloc
# print(self.total_time)
print(best_depth - 1)
self.eval_depth = best_depth - 1
return move
def set_player_colour(self, colour):
self.player = colour
self.opponent = Board.get_opp_piece_type(colour)
# get the current time in milliseconds
@staticmethod
def curr_millisecond_time():
return int(time() * 1000)
'''
NEGAMAX DRIVER FUNCTION -- THIS IMPLEMENTS THE FOLLOWING:
- NEGAMAX WITH A TRANSPOSITION TABLE
- MOVE ORDERING USING THE BEST MOVE WE HAVE FOUND SO FAR (IF IT EXISTS IN THE TRANSPOSITION TABLE)
- MOVE ORDERING OF THE MOVES WE THINK TO BE FAVOURABLE USING A LIGHTWEIGHT EVALUATION FUNCTION
- SELECTING ONLY THE TOP FAVOURABLE MOVES TO EVALUATE USING MINIMAX -- THIS IS HEAVY GREEDY PRUNING
APPLIED TO NEGAMAX DESIGNED SUCH THAT WE ONLY LOOK AT MOVES THAT WE THINK WILL PRODUCE A GOOD OUTCOME,
THUS PRUNING ANY MOVES THAT HAVE A HIGH CHANGE OF HAVING NO EFFECT ON THE GAME-STATE UTILITY.
'''
def negamax(self, depth, alpha, beta, colour):
# print(self.board.board_state)
# Timeout handling
self.time_end = self.curr_millisecond_time()
if self.time_end - self.time_start > self.time_rem:
raise TimeOut
opponent = Board.get_opp_piece_type(colour)
original_alpha = alpha
dic = {self.player: 1, self.opponent: -1}
move_to_try = None
# check if the current board state is in the transposition table
board_str = self.board.board_state.decode("utf-8")
key = self.tt.contains(board_str, colour, phase=self.board.phase)
if key is not None:
# get the value mappings from the dictionary
board_str = key[0]
entry = self.tt.get_entry(board_str, colour)
tt_value = entry[0]
tt_type = entry[1]
tt_best_move = entry[2]
tt_depth = entry[3]
# if we have found an entry in the transposition table, then the move
# we should try first is this best move
move_to_try = tt_best_move
if tt_depth >= depth:
# this is the PV node therefore this is the best move that we have found so far
if tt_type == constant.TT_EXACT:
return tt_value, tt_best_move
# the minimax value in the transposition table is a lower bound to the search
elif tt_type == constant.TT_LOWER:
if tt_value > alpha:
alpha = tt_value
# the value in the table corresponds to a beta cutoff and therefore it is an upper bound for beta
elif tt_type == constant.TT_UPPER:
if tt_value < beta:
beta = tt_value
# test for cutoff -- return the best move found so far
if alpha >= beta:
return tt_value, tt_best_move
# obtain the actions and sort them
actions = self.board.update_actions(colour)
actions = self.board.sort_actions(actions, colour)
# terminal test -- default case
if self.cutoff_test(depth):
val = self.evaluate_state(self.board, self.player,
actions) * dic[colour]
return val, None
# do the negamax search search
best_val = -inf
best_action = None
# if we have found a best action to take in the transposition table, this should be the first
# move we should try -- put this at the start of the list of actions
if move_to_try is not None and move_to_try in actions:
# put the move to try at the first position -- therefore it will be searched first
actions = [move_to_try] + actions
i = 0
# split the list of actions into favourable and unfavourable actions
# we only consider to search teh favourable actions if the action list is long enough
if len(actions) <= 12:
favourable = actions
elif 12 < len(actions) < 20:
favourable = actions[:12]
else:
favourable = actions[:len(actions) // 2]
# iterate only through the favourable moves, ensuring that the number of moves is not too big
# the aim is to reduce the branching factor as much as we can, but also having enough moves to
# evaluate such that we get the part of the optimality decision making from negamax/minimax
# rather than a purely greedy approach.
# print(len(favourable))
for action in favourable:
# skip over the best action in the tt table -- this action has already be searched
if action == move_to_try and i != 0:
continue
i += 1
# update the board, record the eliminated pieces from that update
elim = self.board.update_board(action, colour)
score, temp = self.negamax(depth - 1, -beta, -alpha, opponent)
score = -score
# undo the action applied to the board
self.undo_action(action, colour, elim)
# get the best score and action so far
if score > best_val:
best_val = score
best_action = action
# update alpha if needed
if best_val > alpha:
alpha = best_val
# test for cut off
if alpha >= beta:
break
# store the values in the transposition table
if best_val <= original_alpha:
# then this is an upper bound
tt_type = constant.TT_UPPER
elif best_val >= beta:
# if the best value we have found is a lower bound
tt_type = constant.TT_LOWER
# print("LOWER")
else:
# this is the PV node value
tt_type = constant.TT_EXACT
# add the entry to the transposition table
self.tt.add_entry(self.board.board_state, colour, best_val, tt_type,
best_action, depth)
return best_val, best_action
# cut-off test -- either depth is zero or the board is at terminal state
def cutoff_test(self, depth):
if depth == 0:
return True
if self.is_terminal():
return True
return False
# evaluate the game state
def evaluate_state(self, board, colour, actions):
return self.evaluation.evaluate(board, colour, actions)
# update the negamax board representation for another search
def update_board(self, board):
self.board = deepcopy(board)
# terminal state check
def is_terminal(self):
return self.board.is_terminal()
# undo board wrapper
def undo_action(self, action, colour, elim):
return self.board.undo_action(action, colour, elim)
class Negamax(object):
def __init__(self, board, colour):
# we want to create a node
self.tt = TranspositionTable()
# only use this board to complete the search
# save memory
self.board = deepcopy(board)
# for alpha beta search -- instead of passing it into the function calls we can use this
self.alpha = -inf
self.beta = inf
# defines the colours of min and max
self.player = colour
self.opponent = Board.get_opp_piece_type(self.player)
# default depth
self.depth = inf
# default move ordering with iterative deepening
self.actions_evaluated = []
self.actions_leftover = []
# data structures for machine learning
self.eval_depth = 0
self.minimax_val = 0
self.policy_vector = []
# generate the actions for the start of the game
# self.generate_actions()
self.undo_effected = []
self.time_alloc = 0
self.time_rem = 0
self.time_start = 0
self.time_end = 0
self.evaluation = Evaluation("./XML", "/eval_weights")
'''
* Alpha Beta - Minimax Driver Function
'''
def itr_negamax(self):
# clear the transposition table every time we make a new move -- this is to ensure that it doesn't grow too big
# if self.board.phase == constant.MOVING_PHASE and self.board.move_counter == 0:
#if self.board.phase == constant.PLACEMENT_PHASE:
self.tt.clear()
# update the root number of pieces every time we do a search on a new node
self.board.root_num_black = len(self.board.black_pieces)
self.board.root_num_white = len(self.board.white_pieces)
# default policy
available_actions = self.board.update_actions(self.player)
action_set = set(available_actions)
# self.actions_leftover = self.board.update_actions(self.board, self.player)
if len(available_actions) == 0:
return None
#else:
# lets just set the default to the first move
# move = available_actions[0]
# time allocated per move in ms
'''
self.time_alloc = 0
if self.board.phase == constant.PLACEMENT_PHASE:
self.time_alloc = (30000 - self.time_alloc) / (24 - self.board.move_counter)
else:
self.time_alloc = (30000 - self.time_alloc) / (100 - self.board.move_counter)
'''
# self.time_alloc = 5000
# time allocated per move in ms
self.time_alloc = 0
total = 120000
if self.board.phase == constant.PLACEMENT_PHASE:
#self.time_alloc = (total/2 - self.time_alloc) / (24 - self.board.move_counter)
#total -= self.time_alloc
self.time_alloc = 3000
else:
#self.time_alloc = (total - self.time_alloc) / (100 - self.board.move_counter)
#total -= self.time_alloc
self.time_alloc = 800
# get time
start_time = Negamax.curr_millisecond_time()
best_depth = 1
val, move = 0, None
# iterative deepening begins here
best_move = None
for depth in range(1, MAX_ITER):
print(depth)
try:
self.time_rem = self.time_alloc
self.time_start = self.curr_millisecond_time()
val, move = self.negamax(depth, -inf, inf, self.player)
self.time_end = self.curr_millisecond_time()
self.time_rem = self.time_alloc - (self.time_end -
self.time_start)
print(move)
best_depth += 1
# if we have a move that is not none lets always pick that move that is legal
# becuase we are doing a greedy search -- it sometimes returns an illegal move, not too sure why
# therefore here we check if a move is legal as well
if move is not None and move in action_set:
best_move = move
# print(self.board)
# print("sdfsfsfsfsfsdfsfsdfs")
except TimeOut:
break
self.eval_depth = best_depth
return best_move
def set_player_colour(self, colour):
self.player = colour
self.opponent = Board.get_opp_piece_type(colour)
@staticmethod
def curr_millisecond_time():
return int(time() * 1000)
# naive Negamax (depth limited) -- No Transposition Table
def negamax(self, depth, alpha, beta, colour):
# Timeout handling
self.time_end = self.curr_millisecond_time()
if self.time_end - self.time_start > self.time_rem:
raise TimeOut
opponent = Board.get_opp_piece_type(colour)
# for evaluation
dic = {self.player: 1, self.opponent: -1}
# generate legal actions
actions = self.board.update_actions(colour)
# terminal test -- default case
if self.cutoff_test(depth):
val = self.evaluate_state(self.board, self.player,
actions) * dic[colour]
return val, None
# do the minimax search
best_val = -inf
best_action = None
#print(self.board)
#print(actions)
#print(self.board.white_pieces)
# print(self.board.black_pieces)
# generate legal actions
# actions = self.board.update_actions(colour)
# print("THESE ACTIONS----------------")
# print(actions)
# print(self.board)
# print("*"*30)
for action in actions:
# print("THIS CALL--------")
# print(self.board)
# print("THIS CALL--------")
# if self.board.phase == constant.MOVING_PHASE:
# piece = self.board.get_piece(action[0])
# direction = action[1]
# if piece.is_legal_move(direction) is False:
# print(actions)
# print(self)
# print("WHYYYYYYYYYYYYYY--------------------------------------------")
# print(action[0], direction, colour)
# print(piece)
# print(piece.get_legal_actions())
elim = self.board.update_board(action, colour)
score, temp = self.negamax(depth - 1, -beta, -alpha, opponent)
self.undo_action(action, colour, elim)
score = -score
if score > best_val:
best_val = score
best_action = action
if score > alpha:
alpha = score
if alpha >= beta:
break
return best_val, best_action
def cutoff_test(self, depth):
if depth == 0:
return True
if self.is_terminal():
return True
return False
def evaluate_state(self, board, colour, actions):
# return len(self.board.white_pieces) - len(self.board.black_pieces)
return self.evaluation.evaluate(board, colour, actions)
# update the available moves of the search algorithm after it has been instantiated
#
# def update_available_moves(self, node, available_moves):
# node.available_moves = available_moves
def update_board(self, board):
self.board = deepcopy(board)
def is_terminal(self):
return self.board.is_terminal()
def undo_action(self, action, colour, elim_pieces):
self.board.undo_action(action, colour, elim_pieces)