planning.py (aimacode#232)

Chipe1 · norvig · commit 2f84be4bb4c1 · 2016-05-21T22:28:39.000-07:00
* Added Action class for PDDL

* Added tests for Action class

* Changed doc string

* Added PDLL class

* Added Air-Cargo-problem

* Tested Air Cargo Problem
diff --git a/planning.py b/planning.py
@@ -1,13 +1,134 @@
 """Planning (Chapters 10-11)
 """
 
-# flake8: noqa
+from utils import Expr, expr, first
+from logic import FolKB
 
-import agents
+class PDLL:
+    """
+    PDLL used to deine a search problem
+    It stores states in a knowledge base consisting of first order logic statements
+    The conjunction of these logical statements completely define a state
+    """
 
-import math
-import random
-import sys
-import time
-import bisect
-import string
+    def __init__(self, initial_state, actions, goal_test):
+        self.kb = FolKB(initial_state)
+        self.actions = actions
+        self.goal_test_func = goal_test
+
+    def goal_test(self):
+        return self.goal_test_func(self.kb)
+
+    def act(self, action):
+        """
+        Performs the action given as argument
+        Note that action is an Expr like expr('Remove(Glass, Table)') or expr('Eat(Sandwich)')
+        """
+        action_name = action.op
+        args = action.args
+        list_action = first(a for a in self.actions if a.name == action_name)
+        if list_action is None:
+            raise Exception("Action '{}' not found".format(action_name))
+        if not list_action.check_precond(self.kb, args):
+            raise Exception("Action '{}' pre-conditions not satisfied".format(action))
+        list_action(self.kb, args)
+
+class Action:
+    """
+    Defines an action schema using preconditions and effects
+    Use this to describe actions in PDDL
+    action is an Expr where variables are given as arguments(args)
+    Precondition and effect are both lists with positive and negated literals
+    Example:
+    precond_pos = [expr("Human(person)"), expr("Hungry(Person)")]
+    precond_neg = [expr("Eaten(food)")]
+    effect_add = [expr("Eaten(food)")]
+    effect_rem = [expr("Hungry(person)")]
+    eat = Action(expr("Eat(person, food)"), [precond_pos, precond_neg], [effect_add, effect_rem])
+    """
+
+    def __init__(self,action , precond, effect):
+        self.name = action.op
+        self.args = action.args
+        self.precond_pos = precond[0]
+        self.precond_neg = precond[1]
+        self.effect_add = effect[0]
+        self.effect_rem = effect[1]
+
+    def __call__(self, kb, args):
+        return self.act(kb, args)
+
+    def substitute(self, e, args):
+        """Replaces variables in expression with their respective Propostional symbol"""
+        new_args = [args[i] for x in e.args for i in range(len(self.args)) if self.args[i]==x]
+        return Expr(e.op, *new_args)
+
+    def check_precond(self, kb, args):
+        """Checks if the precondition is satisfied in the current state"""
+        #check for positive clauses
+        for clause in self.precond_pos:
+            if self.substitute(clause, args) not in kb.clauses:
+                return False
+        #check for negative clauses
+        for clause in self.precond_neg:
+            if self.substitute(clause, args) in kb.clauses:
+                return False
+        return True
+
+    def act(self, kb, args):
+        """Executes the action on the state's kb"""
+        #check if the preconditions are satisfied
+        if not self.check_precond(kb, args):
+            raise Exception("Action pre-conditions not satisfied")
+        #remove negative literals
+        for clause in self.effect_rem:
+            kb.retract(self.substitute(clause, args))
+        #add positive literals
+        for clause in self.effect_add:
+            kb.tell(self.substitute(clause, args))
+
+
+def air_cargo():
+    init = [expr('At(C1, SFO)'),
+            expr('At(C2, JFK)'),
+            expr('At(P1, SFO)'),
+            expr('At(P2, JFK)'),
+            expr('Cargo(C1)'),
+            expr('Cargo(C2)'),
+            expr('Plane(P1)'),
+            expr('Plane(P2)'),
+            expr('Airport(JFK)'),
+            expr('Airport(SFO)')]
+    
+    def goal_test(kb):
+        required = [expr('At(C1 , JFK)'), expr('At(C2 ,SFO)')]
+        for q in required:
+            if kb.ask(q) is False:
+                return False
+        return True
+
+    ## Actions
+    #  Load
+    precond_pos = [expr("At(c, a)"), expr("At(p, a)"), expr("Cargo(c)"), expr("Plane(p)"), expr("Airport(a)")]
+    precond_neg = []
+    effect_add = [expr("In(c, p)")]
+    effect_rem = [expr("At(c, a)")]
+    load = Action(expr("Load(c, p, a)"), [precond_pos, precond_neg], [effect_add, effect_rem])
+
+    #  Unload
+    precond_pos = [expr("In(c, p)"), expr("At(p, a)"), expr("Cargo(c)"), expr("Plane(p)"), expr("Airport(a)")]
+    precond_neg = []
+    effect_add = [expr("At(c, a)")]
+    effect_rem = [expr("In(c, p)")]
+    unload = Action(expr("Unload(c, p, a)"), [precond_pos, precond_neg], [effect_add, effect_rem])
+
+    #  Load
+    #  Used used 'f' instead of 'from' because 'from' is a python keyword and expr uses eval() function
+    precond_pos = [expr("At(p, f)"), expr("Plane(p)"), expr("Airport(f)"), expr("Airport(to)")]
+    precond_neg = []
+    effect_add = [expr("At(p, to)")]
+    effect_rem = [expr("At(p, f)")]
+    fly = Action(expr("Fly(p, f, to)"), [precond_pos, precond_neg], [effect_add, effect_rem])
+
+    return PDLL(init, [load, unload, fly], goal_test)
+    
diff --git a/tests/test_planning.py b/tests/test_planning.py
@@ -0,0 +1,34 @@
+from planning import *
+from utils import expr
+from logic import FolKB
+
+def test_action():
+    precond = [[expr("P(x)"), expr("Q(y, z)")]
+               ,[expr("Q(x)")]]
+    effect = [[expr("Q(x)")]
+              , [expr("P(x)")]]
+    a=Action(expr("A(x,y,z)"),precond, effect)
+    args = [expr("A"), expr("B"), expr("C")]
+    assert a.substitute(expr("P(x, z, y)"), args) == expr("P(A, C, B)")
+    test_kb = FolKB([expr("P(A)"), expr("Q(B, C)"), expr("R(D)")])
+    assert a.check_precond(test_kb, args)
+    a.act(test_kb, args)
+    assert test_kb.ask(expr("P(A)")) is False
+    assert test_kb.ask(expr("Q(A)")) is not False
+    assert test_kb.ask(expr("Q(B, C)")) is not False
+    assert not a.check_precond(test_kb, args)
+
+def test_air_cargo():
+    p = air_cargo()
+    assert p.goal_test() is False
+    solution =[expr("Load(C1 , P1, SFO)"),
+               expr("Fly(P1, SFO, JFK)"),
+               expr("Unload(C1, P1, JFK)"),
+               expr("Load(C2, P2, JFK)"),
+               expr("Fly(P2, JFK, SFO)"),
+               expr("Unload (C2, P2, SFO)")]
+
+    for action in solution:
+        p.act(action)
+
+    assert p.goal_test()
