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Assemble all backgammon code in a single class #868

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Merged
norvig merged 3 commits into from
Mar 20, 2018
Merged

Assemble all backgammon code in a single class #868

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f54eda5
Remove BackgammonBoard class
AdityaDaflapurkar Mar 17, 2018
ef9222c
Merge with master
AdityaDaflapurkar Mar 18, 2018
21d105d
Refactor code
AdityaDaflapurkar Mar 18, 2018
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59 changes: 26 additions & 33 deletions games.py
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,7 @@ def max_value(state, dice_roll):
game.dice_roll = dice_roll
return v

def min_value(state, dice_roll):
def min_value(state, dice_roll):
v = infinity
for a in game.actions(state):
v = min(v, chance_node(state, a))
Expand Down Expand Up @@ -395,10 +395,21 @@ class Backgammon(Game):
rolling a pair of dice."""

def __init__(self):
"""Initial state of the game"""
self.dice_roll = (-random.randint(1, 6), -random.randint(1, 6))
board = BackgammonBoard()
# TODO : Add bar to Board class where a blot is placed when it is hit.
point = {'W':0, 'B':0}
self.board = [point.copy() for index in range(24)]
self.board[0]['B'] = self.board[23]['W'] = 2
self.board[5]['W'] = self.board[18]['B'] = 5
self.board[7]['W'] = self.board[16]['B'] = 3
self.board[11]['B'] = self.board[12]['W'] = 5
self.allow_bear_off = {'W': False, 'B': False}

self.initial = GameState(to_move='W',
utility=0, board=board, moves=self.get_all_moves(board, 'W'))
utility=0,
board=self.board,
moves=self.get_all_moves(self.board, 'W'))

def actions(self, state):
"""Returns a list of legal moves for a state."""
Expand All @@ -409,16 +420,16 @@ def actions(self, state):
legal_moves = []
for move in moves:
board = copy.deepcopy(state.board)
if board.is_legal_move(move, self.dice_roll, player):
if self.is_legal_move(move, self.dice_roll, player):
legal_moves.append(move)
return legal_moves

def result(self, state, move):
board = copy.deepcopy(state.board)
player = state.to_move
board.move_checker(move[0], self.dice_roll[0], player)
self.move_checker(move[0], self.dice_roll[0], player)
if len(move) == 2:
board.move_checker(move[1], self.dice_roll[1], player)
self.move_checker(move[1], self.dice_roll[1], player)
to_move = ('W' if player == 'B' else 'B')
return GameState(to_move=to_move,
utility=self.compute_utility(board, move, player),
Expand All @@ -438,10 +449,10 @@ def get_all_moves(self, board, player):
"""All possible moves for a player i.e. all possible ways of
choosing two checkers of a player from the board for a move
at a given state."""
all_points = board.points
all_points = board
taken_points = [index for index, point in enumerate(all_points)
if point[player] > 0]
if board.checkers_at_home(player) == 1:
if self.checkers_at_home(player) == 1:
return [(taken_points[0], )]
moves = list(itertools.permutations(taken_points, 2))
moves = moves + [(index, index) for index, point in enumerate(all_points)
Expand All @@ -453,7 +464,7 @@ def display(self, state):
board = state.board
player = state.to_move
print("Current State : ")
for index, point in enumerate(board.points):
for index, point in enumerate(board):
if point['W'] != 0 or point['B'] != 0:
print("Point : ", index, " W : ", point['W'], " B : ", point['B'])
print("To play : ", player)
Expand All @@ -462,37 +473,19 @@ def compute_utility(self, board, move, player):
"""If 'W' wins with this move, return 1; if 'B' wins return -1; else return 0."""
count = 0
for idx in range(0, 24):
count = count + board.points[idx][player]
count = count + board[idx][player]
if player == 'W' and count == 0:
return 1
if player == 'B' and count == 0:
return -1
return 0


class BackgammonBoard:
"""The board consists of 24 points. Each player('W' and 'B') initially
has 15 checkers on board. Player 'W' moves from point 23 to point 0
and player 'B' moves from point 0 to 23. Points 0-7 are
home for player W and points 17-24 are home for B."""

def __init__(self):
"""Initial state of the game"""
# TODO : Add bar to Board class where a blot is placed when it is hit.
point = {'W':0, 'B':0}
self.points = [point.copy() for index in range(24)]
self.points[0]['B'] = self.points[23]['W'] = 2
self.points[5]['W'] = self.points[18]['B'] = 5
self.points[7]['W'] = self.points[16]['B'] = 3
self.points[11]['B'] = self.points[12]['W'] = 5
self.allow_bear_off = {'W': False, 'B': False}

def checkers_at_home(self, player):
"""Return the no. of checkers at home for a player."""
sum_range = range(0, 7) if player == 'W' else range(17, 24)
count = 0
for idx in sum_range:
count = count + self.points[idx][player]
count = count + self.board[idx][player]
return count

def is_legal_move(self, start, steps, player):
Expand All @@ -504,7 +497,7 @@ def is_legal_move(self, start, steps, player):
dest_range = range(0, 24)
move1_legal = move2_legal = False
if dest1 in dest_range:
if self.is_point_open(player, self.points[dest1]):
if self.is_point_open(player, self.board[dest1]):
self.move_checker(start[0], steps[0], player)
move1_legal = True
else:
Expand All @@ -514,7 +507,7 @@ def is_legal_move(self, start, steps, player):
if not move1_legal:
return False
if dest2 in dest_range:
if self.is_point_open(player, self.points[dest2]):
if self.is_point_open(player, self.board[dest2]):
move2_legal = True
else:
if self.allow_bear_off[player]:
Expand All @@ -525,9 +518,9 @@ def move_checker(self, start, steps, player):
"""Move a checker from starting point by a given number of steps"""
dest = start + steps
dest_range = range(0, 24)
self.points[start][player] -= 1
self.board[start][player] -= 1
if dest in dest_range:
self.points[dest][player] += 1
self.board[dest][player] += 1
if self.checkers_at_home(player) == 15:
self.allow_bear_off[player] = True

Expand Down