def max_play(state, limit, oppColor=BLACKCELL):
limit -= 1
if is_gameover(state) or limit <= 0:
state_value = evaluate(state, oppColor)
return state_value
states = obj.getNextStates(state)
if (states):
return max(map(lambda state: min_play(state, limit, state.whoDidThis), states))
else:
state.reverse_State()
return min_play(state, limit)
def minimize(grid, alpha, beta, exploredStates, depth, startTime):
emptyCells = grid.getAvailableCells()
possibleNewTiles = [2, 4]
# terminal test
if not depth or not emptyCells:
# is terminal
return (evaluate(grid), False)
if time.clock() - startTime > 0.08:
return (None, True)
minUtility = float("inf")
# explore all available children
for emptyCell in emptyCells:
for possibleNewTile in possibleNewTiles:
# get the current child
child = grid.clone()
child.insertTile(emptyCell, possibleNewTile)
childUtility = None
if child not in exploredStates:
# get the evaulated value of the child state
(_, childUtility, timeout) = maximize(child, alpha, beta,
exploredStates,
depth - 1, startTime)
if timeout:
return (None, True)
exploredStates[child] = childUtility
else:
childUtility = exploredStates[child]
print "we've explored this state before"
if childUtility < minUtility:
minUtility = childUtility
if alpha >= minUtility:
# pruning the rest of the branches
break
if beta > minUtility:
beta = minUtility
return (minUtility, False)
def maximize(grid, alpha, beta, exploredStates, depth, startTime):
availableMoves = grid.getAvailableMoves()
# terminal test
if not depth or not availableMoves:
# is terminal
return (None, evaluate(grid), False)
# if we are out of time
if time.clock() - startTime > 0.08:
return (None, None, True)
(bestMove, maxUtility) = (None, float("-inf"))
for move in availableMoves:
# get the current child
child = grid.clone()
child.move(move)
childUtility = None
if child not in exploredStates:
# get the evaulated value of the child state
(childUtility, timeout) = minimize(child, alpha, beta,
exploredStates, depth - 1,
startTime)
if timeout:
return (None, maxUtility, True)
exploredStates[child] = childUtility
else:
childUtility = exploredStates[child]
print "we've explored this state before"
if childUtility > maxUtility:
maxUtility = childUtility
bestMove = move
if maxUtility >= beta:
# pruning the rest of the branches
break
if maxUtility > alpha:
alpha = maxUtility
return (bestMove, maxUtility, False)
from Grid import Grid from Displayer import Displayer from StateEvaluator import evaluate grid = Grid(4) displayer = Displayer() grid.insertTile((0, 0), 32) grid.insertTile((1, 0), 16) grid.insertTile((2, 0), 8) grid.insertTile((3, 0), 4) grid.insertTile((2, 1), 2) grid.insertTile((3, 1), 4) grid.insertTile((3, 2), 4) displayer.display(grid) print "evalation: ", evaluate(grid)