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my_planning_graph.py
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my_planning_graph.py
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from aimacode.planning import Action
from aimacode.search import Problem
from aimacode.utils import expr
from lp_utils import decode_state
class PgNode():
"""Base class for planning graph nodes.
includes instance sets common to both types of nodes used in a planning graph
parents: the set of nodes in the previous level
children: the set of nodes in the subsequent level
mutex: the set of sibling nodes that are mutually exclusive with this node
"""
def __init__(self):
self.parents = set()
self.children = set()
self.mutex = set()
def is_mutex(self, other) -> bool:
"""Boolean test for mutual exclusion
:param other: PgNode
the other node to compare with
:return: bool
True if this node and the other are marked mutually exclusive (mutex)
"""
if other in self.mutex:
return True
return False
def show(self):
"""helper print for debugging shows counts of parents, children, siblings
:return:
print only
"""
print("{} parents".format(len(self.parents)))
print("{} children".format(len(self.children)))
print("{} mutex".format(len(self.mutex)))
class PgNode_s(PgNode):
"""A planning graph node representing a state (literal fluent) from a
planning problem.
Args:
----------
symbol : str
A string representing a literal expression from a planning problem
domain.
is_pos : bool
Boolean flag indicating whether the literal expression is positive or
negative.
"""
def __init__(self, symbol: str, is_pos: bool):
"""S-level Planning Graph node constructor
:param symbol: expr
:param is_pos: bool
Instance variables calculated:
literal: expr
fluent in its literal form including negative operator if applicable
Instance variables inherited from PgNode:
parents: set of nodes connected to this node in previous A level; initially empty
children: set of nodes connected to this node in next A level; initially empty
mutex: set of sibling S-nodes that this node has mutual exclusion with; initially empty
"""
PgNode.__init__(self)
self.symbol = symbol
self.is_pos = is_pos
self.__hash = None
def show(self):
"""helper print for debugging shows literal plus counts of parents,
children, siblings
:return:
print only
"""
if self.is_pos:
print("\n*** {}".format(self.symbol))
else:
print("\n*** ~{}".format(self.symbol))
PgNode.show(self)
def __eq__(self, other):
"""equality test for nodes - compares only the literal for equality
:param other: PgNode_s
:return: bool
"""
return (isinstance(other, self.__class__) and
self.is_pos == other.is_pos and
self.symbol == other.symbol)
def __hash__(self):
self.__hash = self.__hash or hash(self.symbol) ^ hash(self.is_pos)
return self.__hash
class PgNode_a(PgNode):
"""A-type (action) Planning Graph node - inherited from PgNode """
def __init__(self, action: Action):
"""A-level Planning Graph node constructor
:param action: Action
a ground action, i.e. this action cannot contain any variables
Instance variables calculated:
An A-level will always have an S-level as its parent and an S-level as its child.
The preconditions and effects will become the parents and children of the A-level node
However, when this node is created, it is not yet connected to the graph
prenodes: set of *possible* parent S-nodes
effnodes: set of *possible* child S-nodes
is_persistent: bool True if this is a persistence action, i.e. a no-op action
Instance variables inherited from PgNode:
parents: set of nodes connected to this node in previous S level; initially empty
children: set of nodes connected to this node in next S level; initially empty
mutex: set of sibling A-nodes that this node has mutual exclusion with; initially empty
"""
PgNode.__init__(self)
self.action = action
self.prenodes = self.precond_s_nodes()
self.effnodes = self.effect_s_nodes()
self.is_persistent = self.prenodes == self.effnodes
self.__hash = None
def show(self):
"""helper print for debugging shows action plus counts of parents, children, siblings
:return:
print only
"""
print("\n*** {!s}".format(self.action))
PgNode.show(self)
def precond_s_nodes(self):
"""precondition literals as S-nodes (represents possible parents for this node).
It is computationally expensive to call this function; it is only called by the
class constructor to populate the `prenodes` attribute.
:return: set of PgNode_s
"""
nodes = set()
for p in self.action.precond_pos:
nodes.add(PgNode_s(p, True))
for p in self.action.precond_neg:
nodes.add(PgNode_s(p, False))
return nodes
def effect_s_nodes(self):
"""effect literals as S-nodes (represents possible children for this node).
It is computationally expensive to call this function; it is only called by the
class constructor to populate the `effnodes` attribute.
:return: set of PgNode_s
"""
nodes = set()
for e in self.action.effect_add:
nodes.add(PgNode_s(e, True))
for e in self.action.effect_rem:
nodes.add(PgNode_s(e, False))
return nodes
def __eq__(self, other):
"""equality test for nodes - compares only the action name for equality
:param other: PgNode_a
:return: bool
"""
return (isinstance(other, self.__class__) and
self.is_persistent == other.is_persistent and
self.action.name == other.action.name and
self.action.args == other.action.args)
def __hash__(self):
self.__hash = self.__hash or hash(self.action.name) ^ hash(self.action.args)
return self.__hash
def mutexify(node1: PgNode, node2: PgNode):
""" adds sibling nodes to each other's mutual exclusion (mutex) set. These should be sibling nodes!
:param node1: PgNode (or inherited PgNode_a, PgNode_s types)
:param node2: PgNode (or inherited PgNode_a, PgNode_s types)
:return:
node mutex sets modified
"""
if type(node1) != type(node2):
raise TypeError('Attempted to mutex two nodes of different types')
node1.mutex.add(node2)
node2.mutex.add(node1)
class PlanningGraph():
"""
A planning graph as described in chapter 10 of the AIMA text. The planning
graph can be used to reason about
"""
def __init__(self, problem: Problem, state: str, serial_planning=True):
"""
:param problem: PlanningProblem (or subclass such as AirCargoProblem or HaveCakeProblem)
:param state: str (will be in form TFTTFF... representing fluent states)
:param serial_planning: bool (whether or not to assume that only one action can occur at a time)
Instance variable calculated:
fs: FluentState
the state represented as positive and negative fluent literal lists
all_actions: list of the PlanningProblem valid ground actions combined with calculated no-op actions
s_levels: list of sets of PgNode_s, where each set in the list represents an S-level in the planning graph
a_levels: list of sets of PgNode_a, where each set in the list represents an A-level in the planning graph
"""
self.problem = problem
self.fs = decode_state(state, problem.state_map)
self.serial = serial_planning
self.all_actions = self.problem.actions_list + self.noop_actions(self.problem.state_map)
self.s_levels = []
self.a_levels = []
self.create_graph()
def noop_actions(self, literal_list):
"""create persistent action for each possible fluent
"No-Op" actions are virtual actions (i.e., actions that only exist in
the planning graph, not in the planning problem domain) that operate
on each fluent (literal expression) from the problem domain. No op
actions "pass through" the literal expressions from one level of the
planning graph to the next.
The no-op action list requires both a positive and a negative action
for each literal expression. Positive no-op actions require the literal
as a positive precondition and add the literal expression as an effect
in the output, and negative no-op actions require the literal as a
negative precondition and remove the literal expression as an effect in
the output.
This function should only be called by the class constructor.
:param literal_list:
:return: list of Action
"""
action_list = []
for fluent in literal_list:
act1 = Action(expr("Noop_pos({})".format(fluent)), ([fluent], []), ([fluent], []))
action_list.append(act1)
act2 = Action(expr("Noop_neg({})".format(fluent)), ([], [fluent]), ([], [fluent]))
action_list.append(act2)
return action_list
def create_graph(self):
""" build a Planning Graph as described in Russell-Norvig 3rd Ed 10.3 or 2nd Ed 11.4
The S0 initial level has been implemented for you. It has no parents and includes all of
the literal fluents that are part of the initial state passed to the constructor. At the start
of a problem planning search, this will be the same as the initial state of the problem. However,
the planning graph can be built from any state in the Planning Problem
This function should only be called by the class constructor.
:return:
builds the graph by filling s_levels[] and a_levels[] lists with node sets for each level
"""
# the graph should only be built during class construction
if (len(self.s_levels) != 0) or (len(self.a_levels) != 0):
raise Exception(
'Planning Graph already created; construct a new planning graph for each new state in the planning sequence')
# initialize S0 to literals in initial state provided.
leveled = False
level = 0
self.s_levels.append(set()) # S0 set of s_nodes - empty to start
# for each fluent in the initial state, add the correct literal PgNode_s
for literal in self.fs.pos:
self.s_levels[level].add(PgNode_s(literal, True))
for literal in self.fs.neg:
self.s_levels[level].add(PgNode_s(literal, False))
# no mutexes at the first level
# continue to build the graph alternating A, S levels until last two S levels contain the same literals,
# i.e. until it is "leveled"
while not leveled:
self.add_action_level(level)
self.update_a_mutex(self.a_levels[level])
level += 1
self.add_literal_level(level)
self.update_s_mutex(self.s_levels[level])
if self.s_levels[level] == self.s_levels[level - 1]:
leveled = True
def add_action_level(self, level):
""" add an A (action) level to the Planning Graph
:param level: int
the level number alternates S0, A0, S1, A1, S2, .... etc the level number is also used as the
index for the node set lists self.a_levels[] and self.s_levels[]
:return:
adds A nodes to the current level in self.a_levels[level]
"""
# TODO add action A level to the planning graph as described in the Russell-Norvig text
# 1. determine what actions to add and create those PgNode_a objects
# 2. connect the nodes to the previous S literal level
# for example, the A0 level will iterate through all possible actions for the problem and add a PgNode_a to a_levels[0]
# set iff all prerequisite literals for the action hold in S0. This can be accomplished by testing
# to see if a proposed PgNode_a has prenodes that are a subset of the previous S level. Once an
# action node is added, it MUST be connected to the S node instances in the appropriate s_level set.
# 5/17/2017 Bhinesh Patel
a_nodes = []
for action in self.all_actions:
# Create an action Node for this action
node_a = PgNode_a(action)
# Check if preconditions for this action are present in the previous literal state level.
if node_a.prenodes.issubset(self.s_levels[level]):
# Action is reachable so add it to the list of action nodes for this level.
a_nodes.append(node_a)
# action node is a child of the preceding level's state nodes
for node_s in self.s_levels[level]:
node_s.children.add(node_a)
# parents of action node are the previous level's state nodes
node_a.parents.add(node_s)
# Add all reachable action nodes to action level.
self.a_levels.append(a_nodes)
def add_literal_level(self, level):
""" add an S (literal) level to the Planning Graph
:param level: int
the level number alternates S0, A0, S1, A1, S2, .... etc the level number is also used as the
index for the node set lists self.a_levels[] and self.s_levels[]
:return:
adds S nodes to the current level in self.s_levels[level]
"""
# TODO add literal S level to the planning graph as described in the Russell-Norvig text
# 1. determine what literals to add
# 2. connect the nodes
# for example, every A node in the previous level has a list of S nodes in effnodes that represent the effect
# produced by the action. These literals will all be part of the new S level. Since we are working with sets, they
# may be "added" to the set without fear of duplication. However, it is important to then correctly create and connect
# all of the new S nodes as children of all the A nodes that could produce them, and likewise add the A nodes to the
# parent sets of the S nodes
# 5/17/2017 Bhinesh Patel
s_nodes = set()
# Get all the actions in the previous level
for node_a in self.a_levels[level - 1]:
# Get the effect nodes for this preceding action and add them to the level's state nodes
for node_s in node_a.effnodes:
# Add this reachable effect node to the set of state nodes
s_nodes.add(node_s)
# preceding level's action node is a parent of this reachable effect node
node_s.parents.add(node_a)
# effect node is a child of the preceding action node
node_a.children.add(node_s)
# Build the state level from the reachable effect nodes
self.s_levels.append(s_nodes)
def update_a_mutex(self, nodeset):
""" Determine and update sibling mutual exclusion for A-level nodes
Mutex action tests section from 3rd Ed. 10.3 or 2nd Ed. 11.4
A mutex relation holds between two actions a given level
if the planning graph is a serial planning graph and the pair are nonpersistence actions
or if any of the three conditions hold between the pair:
Inconsistent Effects
Interference
Competing needs
:param nodeset: set of PgNode_a (siblings in the same level)
:return:
mutex set in each PgNode_a in the set is appropriately updated
"""
nodelist = list(nodeset)
for i, n1 in enumerate(nodelist[:-1]):
for n2 in nodelist[i + 1:]:
if (self.serialize_actions(n1, n2) or
self.inconsistent_effects_mutex(n1, n2) or
self.interference_mutex(n1, n2) or
self.competing_needs_mutex(n1, n2)):
mutexify(n1, n2)
def serialize_actions(self, node_a1: PgNode_a, node_a2: PgNode_a) -> bool:
"""
Test a pair of actions for mutual exclusion, returning True if the
planning graph is serial, and if either action is persistent; otherwise
return False. Two serial actions are mutually exclusive if they are
both non-persistent.
:param node_a1: PgNode_a
:param node_a2: PgNode_a
:return: bool
"""
#
if not self.serial:
return False
if node_a1.is_persistent or node_a2.is_persistent:
return False
return True
def inconsistent_effects_mutex(self, node_a1: PgNode_a, node_a2: PgNode_a) -> bool:
"""
Test a pair of actions for inconsistent effects, returning True if
one action negates an effect of the other, and False otherwise.
HINT: The Action instance associated with an action node is accessible
through the PgNode_a.action attribute. See the Action class
documentation for details on accessing the effects and preconditions of
an action.
:param node_a1: PgNode_a
:param node_a2: PgNode_a
:return: bool
"""
# TODO test for Inconsistent Effects between nodes
# 5/17/2017 Bhinesh Patel
# Check if node_a1's add effects negate node_a2's rem effects
for effect in node_a1.action.effect_add:
if effect in node_a2.action.effect_rem:
return True
# Check if node_a2's add effects negate node_a1's rem effects
for effect in node_a2.action.effect_add:
if effect in node_a1.action.effect_rem:
return True
return False
def interference_mutex(self, node_a1: PgNode_a, node_a2: PgNode_a) -> bool:
"""
Test a pair of actions for mutual exclusion, returning True if the
effect of one action is the negation of a precondition of the other.
HINT: The Action instance associated with an action node is accessible
through the PgNode_a.action attribute. See the Action class
documentation for details on accessing the effects and preconditions of
an action.
:param node_a1: PgNode_a
:param node_a2: PgNode_a
:return: bool
"""
# TODO test for Interference between nodes
# 5/17/2017 Bhinesh Patel
# Check if node_a1's add effects negate node_a2's neg preconditions
for effect in node_a1.action.effect_add:
if effect in node_a2.action.precond_neg:
return True
# Check if node_a2's add effects negate node_a1's neg preconditions
for effect in node_a2.action.effect_add:
if effect in node_a1.action.precond_neg:
return True
# Check if node_a1's rem effects negate node_a2's pos preconditions
for effect in node_a1.action.effect_rem:
if effect in node_a2.action.precond_pos:
return True
# Check if node_a2's rem effects negate node_a1's pos preconditions
for effect in node_a2.action.effect_rem:
if effect in node_a1.action.precond_pos:
return True
return False
def competing_needs_mutex(self, node_a1: PgNode_a, node_a2: PgNode_a) -> bool:
"""
Test a pair of actions for mutual exclusion, returning True if one of
the precondition of one action is mutex with a precondition of the
other action.
:param node_a1: PgNode_a
:param node_a2: PgNode_a
:return: bool
"""
# TODO test for Competing Needs between nodes
# 5/17/2017 Bhinesh Patel
# Check if node_a1's preconditions are mutually exclusive with node_a2's preconditions. Only need to find one.
for pre_node_a1 in node_a1.parents:
for pre_node_a2 in node_a2.parents:
if pre_node_a1.is_mutex(pre_node_a2):
return True
return False
def update_s_mutex(self, nodeset: set):
""" Determine and update sibling mutual exclusion for S-level nodes
Mutex action tests section from 3rd Ed. 10.3 or 2nd Ed. 11.4
A mutex relation holds between literals at a given level
if either of the two conditions hold between the pair:
Negation
Inconsistent support
:param nodeset: set of PgNode_a (siblings in the same level)
:return:
mutex set in each PgNode_a in the set is appropriately updated
"""
nodelist = list(nodeset)
for i, n1 in enumerate(nodelist[:-1]):
for n2 in nodelist[i + 1:]:
if self.negation_mutex(n1, n2) or self.inconsistent_support_mutex(n1, n2):
mutexify(n1, n2)
def negation_mutex(self, node_s1: PgNode_s, node_s2: PgNode_s) -> bool:
"""
Test a pair of state literals for mutual exclusion, returning True if
one node is the negation of the other, and False otherwise.
HINT: Look at the PgNode_s.__eq__ defines the notion of equivalence for
literal expression nodes, and the class tracks whether the literal is
positive or negative.
:param node_s1: PgNode_s
:param node_s2: PgNode_s
:return: bool
"""
# TODO test for negation between nodes
# 5/17/2017 Bhinesh Patel
# Check if two state literals are negative of each other.
return node_s1.symbol == node_s2.symbol and node_s1.is_pos != node_s2.is_pos
def inconsistent_support_mutex(self, node_s1: PgNode_s, node_s2: PgNode_s):
"""
Test a pair of state literals for mutual exclusion, returning True if
there are no actions that could achieve the two literals at the same
time, and False otherwise. In other words, the two literal nodes are
mutex if all of the actions that could achieve the first literal node
are pairwise mutually exclusive with all of the actions that could
achieve the second literal node.
HINT: The PgNode.is_mutex method can be used to test whether two nodes
are mutually exclusive.
:param node_s1: PgNode_s
:param node_s2: PgNode_s
:return: bool
"""
# TODO test for Inconsistent Support between nodes
# 5/17/2017 Bhinesh Patel
# Check if actions that lead to node_s1 can also lead to node_s2
for actions_s1 in node_s1.parents:
for actions_s2 in node_s2.parents:
if not actions_s1.is_mutex(actions_s2):
return False
return True
def h_levelsum(self) -> int:
"""The sum of the level costs of the individual goals (admissible if goals independent)
:return: int
"""
level_sum = 0
# TODO implement
# 5/17/2017 Bhinesh Patel
# For each goal in the problem, determine their level cost, then add them together.
# Find first state the goal is found in and return the level as the cost.
for goal in self.problem.goal:
goal_found = False
for level in range(len(self.s_levels)):
for state in self.s_levels[level]:
if goal == state.symbol and state.is_pos:
goal_found = True
level_sum += level
break
if goal_found:
break
return level_sum