def breadth_first_search(planning_task):
"""
Searches for a plan on the given task using breadth first search and
duplicate detection.
@param planning_task: The planning task to solve.
@return: The solution as a list of operators or None if the task is
unsolvable.
"""
# counts the number of loops (only for printing)
iteration = 0
# fifo-queue storing the nodes which are next to explore
queue = deque()
queue.append(searchspace.make_root_node(planning_task.initial_state))
# set storing the explored nodes, used for duplicate detection
closed = {planning_task.initial_state}
while queue:
iteration += 1
logging.debug("breadth_first_search: Iteration %d, #unexplored=%d" %
(iteration, len(queue)))
# get the next node to explore
node = queue.popleft()
# exploring the node or if it is a goal node extracting the plan
if planning_task.goal_reached(node.state):
logging.info("Goal reached. Start extraction of solution.")
logging.info("%d Nodes expanded" % iteration)
return node.extract_solution()
for operator, successor_state in planning_task.get_successor_states(
node.state):
# duplicate detection
if successor_state not in closed:
queue.append(
searchspace.make_child_node(node, operator,
successor_state))
# remember the successor state
closed.add(successor_state)
logging.info("No operators left. Task unsolvable.")
logging.info("%d Nodes expanded" % iteration)
return None
"""
Unit Testing for the search space module
"""
from pyperplan.search.searchspace import make_child_node, make_root_node
# Construct a small tree in order to perform some needed test methods
root = make_root_node("state1")
child1 = make_child_node(root, "action1", "state2")
child2 = make_child_node(root, "action2", "state3")
grandchild1 = make_child_node(child1, "action3", "state4")
grandchild2 = make_child_node(child2, "action4", "state5")
def test_extract_solution():
"""
Tests whether extract_solution method within class searchspace returns the
list of actions starting from the root
"""
assert root.extract_solution() == []
assert grandchild1.extract_solution() == ["action1", "action3"]
assert grandchild2.extract_solution() == ["action2", "action4"]
def test_g_values():
"""
Tests whether the distance of the node from the root is computed properly
"""
assert root.g == 0
assert child1.g == 1
finisher1-stack-letter sheet1 dummy-sheet
"""
optimal_plan = [op.strip() for op in optimal_plan.splitlines()]
import os
from pyperplan import planner
from pyperplan.search import breadth_first_search, searchspace
from pyperplan.task import Operator, Task
benchmarks = os.path.abspath(
os.path.join(os.path.abspath(__file__), "../../../../benchmarks"))
# Collect problem files
problem_file = os.path.join(benchmarks, "parcprinter", "task01.pddl")
domain_file = planner.find_domain(problem_file)
problem = planner._parse(domain_file, problem_file)
task = planner._ground(problem)
# Manually do the "search"
node = searchspace.make_root_node(task.initial_state)
for step, op_name in enumerate(optimal_plan, start=1):
for op, successor_state in task.get_successor_states(node.state):
if not op.name.strip("()") == op_name:
continue
node = searchspace.make_child_node(node, op, successor_state)
# Check that we reached the goal
assert len(task.goals - node.state) == 0
def astar_search(
task,
heuristic,
make_open_entry=ordered_node_astar,
use_relaxed_plan=False,
max_search_time=float("inf"),
):
"""
Searches for a plan in the given task using A* search.
@param task The task to be solved
@param heuristic A heuristic callable which computes the estimated steps
from a search node to reach the goal.
@param make_open_entry An optional parameter to change the bahavior of the
astar search. The callable should return a search
node, possible values are ordered_node_astar,
ordered_node_weighted_astar and
ordered_node_greedy_best_first with obvious
meanings.
@param max_search_time Maximum search time in seconds
"""
open = []
state_cost = {task.initial_state: 0}
node_tiebreaker = 0
root = searchspace.make_root_node(task.initial_state)
init_h = heuristic(root)
heapq.heappush(open, make_open_entry(root, init_h, node_tiebreaker))
_log.info("Initial h value: %f" % init_h)
besth = float("inf")
counter = 0
expansions = 0
# Number of heuristic calls, include the initial call for root note
heuristic_calls = 1
# Used so we can interrupt the search
start_time = time.perf_counter()
while open:
# Check whether max search time exceeded
elapsed_time = time.perf_counter() - start_time
if elapsed_time >= max_search_time:
metrics = SearchMetrics(
nodes_expanded=expansions,
plan_length=-1,
heuristic_calls=heuristic_calls,
heuristic_val_for_initial_state=init_h,
search_time=elapsed_time,
search_state=SearchState.timed_out,
)
_log.warning("Search timed out")
_log.info("%d Nodes expanded" % expansions)
_log.info("%d times heuristic called" % heuristic_calls)
return [], metrics
(f, h, _tie, pop_node) = heapq.heappop(open)
if h < besth:
besth = h
_log.debug("Found new best h: %d after %d expansions" %
(besth, counter))
pop_state = pop_node.state
# Only expand the node if its associated cost (g value) is the lowest
# cost known for this state. Otherwise we already found a cheaper
# path after creating this node and hence can disregard it.
if state_cost[pop_state] == pop_node.g:
expansions += 1
if task.goal_reached(pop_state):
_log.info("Goal reached. Start extraction of solution.")
_log.info("%d Nodes expanded" % expansions)
_log.info("%d times heuristic called" % heuristic_calls)
sol = pop_node.extract_solution()
# Create metrics
metrics = SearchMetrics(
nodes_expanded=expansions,
plan_length=len(sol),
heuristic_calls=heuristic_calls,
heuristic_val_for_initial_state=init_h,
search_time=time.perf_counter() - start_time,
search_state=SearchState.success,
)
return sol, metrics
rplan = None
if use_relaxed_plan:
(rh, rplan) = heuristic.calc_h_with_plan(
searchspace.make_root_node(pop_state))
_log.debug("relaxed plan %s " % rplan)
for op, succ_state in task.get_successor_states(pop_state):
if use_relaxed_plan:
if rplan and not op.name in rplan:
# ignore this operator if we use the relaxed plan
# criterion
_log.debug("removing operator %s << not a "
"preferred operator" % op.name)
continue
else:
_log.debug("keeping operator %s" % op.name)
succ_node = searchspace.make_child_node(
pop_node, op, succ_state)
old_succ_g = state_cost.get(succ_state, float("inf"))
if succ_node.g < old_succ_g:
h = heuristic(succ_node)
heuristic_calls += 1
if h == float("inf"):
# don't bother with states that can't reach the goal anyway
continue
# We either never saw succ_state before, or we found a
# cheaper path to succ_state than previously.
node_tiebreaker += 1
heapq.heappush(
open, make_open_entry(succ_node, h, node_tiebreaker))
state_cost[succ_state] = succ_node.g
counter += 1
_log.info("No operators left. Task unsolvable.")
_log.info("%d Nodes expanded" % expansions)
# Create metrics
metrics = SearchMetrics(
nodes_expanded=expansions,
plan_length=-1,
heuristic_calls=heuristic_calls,
heuristic_val_for_initial_state=init_h,
search_time=time.perf_counter() - start_time,
search_state=SearchState.failed,
)
return None, metrics
def enforced_hillclimbing_search(planning_task,
heuristic,
use_preferred_ops=False):
"""
Searches for a plan on the given task using enforced hill climbing and
duplicate detection.
@param planning_task: The planning task to solve.
@return: The solution as a list of operators or None if no solution was
found. Note that enforced hill climbing is an incomplete algorith, so it
may fail to find a solution even though the task is solvable.
"""
# counts the number of loops (only for printing)
iteration = 0
# fifo-queue storing the nodes which are next to explore
queue = deque()
initial_node = searchspace.make_root_node(planning_task.initial_state)
queue.append(initial_node)
best_heuristic_value = heuristic(initial_node)
logging.info("Initial h value: %f" % best_heuristic_value)
# set storing the explored nodes, used for duplicate detection
closed = set()
visited = set()
while queue:
iteration += 1
# get the next node to explore
node = queue.popleft()
# remember the successor state
closed.add(node.state)
visited.add(node.state)
# exploring the node or if it is a goal node extracting the plan
if planning_task.goal_reached(node.state):
logging.info("Goal reached. Start extraction of solution.")
logging.info("%d Nodes expanded" % len(visited))
return node.extract_solution()
# for the preferred operator version --> recompute heuristic and
# relaxed plan
if use_preferred_ops:
(rh, rplan) = heuristic.calc_h_with_plan(node)
logging.debug("relaxed plan %s " % rplan)
for operator, successor_state in planning_task.get_successor_states(
node.state):
# for the preferred operator version ignore all non preferred
# operators
if use_preferred_ops:
if rplan and not operator.name in rplan:
# ignore this operator if we use the relaxed plan criterion
logging.debug("removing operator %s << not a preferred "
"operator" % operator.name)
continue
else:
logging.debug("keeping operator %s" % operator.name)
# duplicate detection
if successor_state not in closed:
successor_node = searchspace.make_child_node(
node, operator, successor_state)
heuristic_value = heuristic(successor_node)
if heuristic_value == float("inf"):
continue
elif heuristic_value < best_heuristic_value:
# Just take the first successor node that has a lower
# heuristic value than the current best_heuristic_value
# and ignore the other successor nodes.
logging.debug("Found new best h: %f after %d expansions" %
(heuristic_value, iteration))
queue.clear()
closed.clear()
best_heuristic_value = heuristic_value
queue.append(successor_node)
break
else:
queue.append(successor_node)
logging.info("Enforced hill climbing failed")
logging.info("%d Nodes expanded" % len(visited))
return None