def runAStar():
initial_state = Problem.CREATE_INITIAL_STATE()
print("Initial State:")
print(Problem.DESCRIBE_STATE(initial_state))
global COUNT, BACKLINKS
COUNT = 0
BACKLINKS = {}
IterativeAStar(initial_state)
print(str(COUNT) + " states examined.")
def backtrace(S):
global BACKLINKS
path = []
while not S == -1:
print(S)
path.append(S)
S = BACKLINKS[Problem.HASHCODE(S)]
path.reverse()
print("Solution path: ")
for s in path:
print(Problem.DESCRIBE_STATE(s))
return path
def IterativeAStar(initial_state):
global COUNT, BACKLINKS
OPEN = []
heappush(OPEN,
(Problem.HEURISTICS[Heuristic](initial_state), initial_state))
CLOSED = []
BACKLINKS[Problem.HASHCODE(initial_state)] = -1
while OPEN != []:
S = heappop(OPEN)[1]
CLOSED.append(S)
if Problem.GOAL_TEST(S):
print(Problem.GOAL_MESSAGE_FUNCTION(S))
backtrace(S)
return
COUNT += 1
if (COUNT % 32) == 0:
print(".", end="")
if (COUNT % 128) == 0:
print("COUNT = " + str(COUNT))
print("len(OPEN)=" + str(len(OPEN)))
print("len(CLOSED)=" + str(len(CLOSED)))
for op in Problem.OPERATORS:
#Optionally uncomment the following when debugging
#a new problem formulation.
#print("Trying operator: "+op.name)
if op.precond(S):
new_state = op.state_transf(S)
if not occurs_in(new_state, CLOSED):
heappush(
OPEN,
(Problem.HEURISTICS[Heuristic](new_state), new_state))
BACKLINKS[Problem.HASHCODE(new_state)] = S
def IterativeDFS(initial_state):
global COUNT, BACKLINKS
OPEN = [initial_state]
CLOSED = []
BACKLINKS[Problem.HASHCODE(initial_state)] = -1
while OPEN != []:
S = OPEN[0]
del OPEN[0]
CLOSED.append(S)
if Problem.GOAL_TEST(S):
print(Problem.GOAL_MESSAGE_FUNCTION(S))
backtrace(S)
return
COUNT += 1
if (COUNT % 32) == 0:
print(".", end="")
if (COUNT % 128) == 0:
print("COUNT = " + str(COUNT))
print("len(OPEN)=" + str(len(OPEN)))
print("len(CLOSED)=" + str(len(CLOSED)))
L = []
for op in Problem.OPERATORS:
#Optionally uncomment the following when debugging
#a new problem formulation.
#print("Trying operator: "+op.name)
if op.precond(S):
new_state = op.state_transf(S)
print(Problem.DESCRIBE_STATE(
new_state)) ##########################################
print()
if not occurs_in(new_state, CLOSED):
L.append(new_state)
BACKLINKS[Problem.HASHCODE(new_state)] = S
#Uncomment for debugging:
#print(Problem.DESCRIBE_STATE(new_state))
for s2 in L:
for i in range(len(OPEN)):
if Problem.DEEP_EQUALS(s2, OPEN[i]):
del OPEN[i]
break
OPEN = L + OPEN
def occurs_in(s1, lst):
for s2 in lst:
if Problem.DEEP_EQUALS(s1, s2): return True
return False