def IterativeAStar(initial_state):
global COUNT, BACKLINKS
OPEN = [initial_state]
CLOSED = []
BACKLINKS[Problem.HASHCODE(initial_state)] = -1
distance = {Problem.HASHCODE(initial_state): 0}
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)
if not occurs_in(new_state, CLOSED):
L.append(new_state)
BACKLINKS[Problem.HASHCODE(new_state)] = S
distance[Problem.HASHCODE(
new_state)] = distance[Problem.HASHCODE(S)] + 1
# 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
OPEN = sorted(
OPEN,
key=lambda state: sort(state) + distance[Problem.HASHCODE(state)])
def occurs_in(s1, lst):
for s2 in lst:
if Problem.DEEP_EQUALS(s1, s2): return True
return False
