def AStar(initial_state):
global COUNT, BACKLINKS
# priority queue with respective priority
# add any auxiliary data structures as needed
OPEN = PriorityQ()
# inserts the initial state with a priority of 0 (priority for initial state is irrelevant to algorithm)
OPEN.insert(initial_state, 0)
CLOSED = []
BACKLINKS[initial_state] = None
while OPEN.__len__() > 0:
# S = min-priority state (priority value gets discarded, only state is looked at)
S = OPEN.deletemin()[0]
while S in CLOSED:
S = OPEN.deletemin()
CLOSED.append(S)
# DO NOT CHANGE THIS SECTION: beginning
if Problem.GOAL_TEST(S):
print(Problem.GOAL_MESSAGE_FUNCTION(S))
path = backtrace(S)
return path, Problem.PROBLEM_NAME
# DO NOT CHANGE THIS SECTION: end
COUNT += 1
# if (COUNT % 32)==0:
if True:
# print(".",end="")
# if (COUNT % 128)==0:
if True:
print("COUNT = " + str(COUNT))
print("len(OPEN)=" + str(len(OPEN)))
print("len(CLOSED)=" + str(len(CLOSED)))
L = []
# looks at all possible new states from operations on S
# if the new state has not already been put on CLOSED, append to L
for op in Problem.OPERATORS:
if op.precond(S):
new_state = op.state_transf(S)
#print(new_state.__str__())
if not occurs_in(new_state, CLOSED):
L.append(new_state)
BACKLINKS[new_state] = S
# adds new states in L into OPEN with their priorities
# if any state already occurs in OPEN...
# if L's state has a lower priority, change OPEN's state priority to L's
# otherwise, keep OPEN's state in OPEN, ignore L's
for state in L:
g_state = G(state)
if OPEN.__contains__(state):
if g_state < OPEN.getpriority(state):
OPEN.remove(state)
else:
break
OPEN.insert(state, g_state)
def AStar(initial_state):
global COUNT, BACKLINKS
# priority queue with respective priority
# add any auxiliary data structures as needed
OPEN = PriorityQ()
CLOSED = []
BACKLINKS[initial_state] = None
g = {initial_state: 0}
OPEN.insert(initial_state, heuristics(initial_state))
while not len(OPEN) == 0:
S, f = OPEN.deletemin()
while S in CLOSED:
S, f = OPEN.deletemin()
CLOSED.append(S)
# DO NOT CHANGE THIS SECTION: begining
if Problem.GOAL_TEST(S):
print(Problem.GOAL_MESSAGE_FUNCTION(S))
path = backtrace(S)
return path, Problem.PROBLEM_NAME
# DO NOT CHANGE THIS SECTION: end
COUNT += 1
print(COUNT)
L = []
for op in Problem.OPERATORS:
if op.precond(S):
new_state = op.state_transf(S)
if not occurs_in(new_state, CLOSED):
L.append(new_state)
BACKLINKS[new_state] = S
if new_state not in g.keys():
g[new_state] = g[S] + 1
for s2 in L:
if s2 in OPEN:
OPEN.remove(s2)
for elt in L:
OPEN.insert(elt, heuristics(elt) + g[elt])
def AStar(initial_state):
global COUNT, BACKLINKS
OPEN = PriorityQ() #currently discovered, not yet evaluated states
CLOSED = [] #already evaluated states
BACKLINKS[initial_state] = None #Tracks most efficient previous step
#Calculate F, G, H scores for Starting state
initialize_scores(initial_state)
#Only one state is known as of now
OPEN.insert(initial_state, F_SCORE[initial_state])
while OPEN.isEmpty() != True:
S, priority = OPEN.deletemin()
while S in CLOSED:
S = OPEN.deletemin()
CLOSED.append(S)
# DO NOT CHANGE THIS SECTION: beginning
if Problem.GOAL_TEST(S):
print(Problem.GOAL_MESSAGE_FUNCTION(S))
path = backtrace(S)
return path, Problem.PROBLEM_NAME
# DO NOT CHANGE THIS SECTION: end
COUNT += 1
if (COUNT % 32) == 0:
# if True:
# print(".",end="")
# if (COUNT % 128*128)==0:
if True:
print("COUNT = " + str(COUNT))
#print("len(OPEN)=" + str(len(OPEN))) #PriorityQ OPEN doesn't have len()
print("len(CLOSED)=" + str(len(CLOSED)))
for op in Problem.OPERATORS:
if op.precond(S):
new_state = op.state_transf(S)
if not occurs_in(new_state,
CLOSED): #ignore already evaluated neighbors
#find tentative score of neighbor
tentative_g_score = G_SCORE[S] + 1
if new_state not in G_SCORE: #Default INFINITY
BACKLINKS[
new_state] = S #First known path to new_state
elif tentative_g_score <= G_SCORE[new_state]:
BACKLINKS[
new_state] = S # Found better path to new_State
else:
continue #current path is not the best path to the neighbor
G_SCORE[new_state] = tentative_g_score
F_SCORE[new_state] = G_SCORE[new_state] + h_score_fn(
new_state)
# Delete previous F-score in PriorityQ if it exists
if OPEN.__contains__(new_state):
OPEN.remove(new_state)
#Update PriorityQ with new priority
OPEN.insert(new_state, F_SCORE[new_state])
# print(Problem.DESCRIBE_STATE(new_state))
#print(OPEN)
#Failure, if goal_test has not succeeded until now
print("COULD NOT FIND GOAL")
return
