# probGraphicalModels.py - Graphical Models and Belief Networks # AIFCA Python3 code Version 0.9.3 Documentation at http://aipython.org # Download the zip file and read aipython.pdf for documentation # Artificial Intelligence: Foundations of Computational Agents http://artint.info # Copyright David L Poole and Alan K Mackworth 2017-2021. # This work is licensed under a Creative Commons # Attribution-NonCommercial-ShareAlike 4.0 International License. # See: http://creativecommons.org/licenses/by-nc-sa/4.0/deed.en from display import Displayable from probFactors import CPD import matplotlib.pyplot as plt class GraphicalModel(Displayable): """The class of graphical models. A graphical model consists of a title, a set of variables and a set of factors. vars is a set of variables factors is a set of factors """ def __init__(self, title, variables=None, factors=None): self.title = title self.variables = variables self.factors = factors class BeliefNetwork(GraphicalModel): """The class of belief networks.""" def __init__(self, title, variables, factors): """vars is a set of variables factors is a set of factors. All of the factors are instances of CPD (e.g., Prob). """ GraphicalModel.__init__(self, title, variables, factors) assert all(isinstance(f,CPD) for f in factors) self.var2cpt = {f.child:f for f in factors} self.var2parents = {f.child:f.parents for f in factors} self.children = {n:[] for n in self.variables} for v in self.var2parents: for par in self.var2parents[v]: self.children[par].append(v) self.topological_sort_saved = None def topological_sort(self): """creates a topological ordering of variables such that the parents of a node are before the node. """ if self.topological_sort_saved: return self.topological_sort_saved next_vars = {n for n in self.var2parents if not self.var2parents[n] } self.display(3,'topological_sort: next_vars',next_vars) top_order=[] while next_vars: var = next_vars.pop() self.display(3,'select variable',var) top_order.append(var) next_vars |= {ch for ch in self.children[var] if all(p in top_order for p in self.var2parents[ch])} self.display(3,'var_with_no_parents_left',next_vars) self.display(3,"top_order",top_order) assert set(top_order)==set(self.var2parents),(top_order,self.var2parents) self.topologicalsort_saved=top_order return top_order def show(self): plt.ion() # interactive ax = plt.figure().gca() ax.set_axis_off() plt.title(self.title) bbox = dict(boxstyle="round4,pad=1.0,rounding_size=0.5") for var in reversed(self.topological_sort()): if self.var2parents[var]: for par in self.var2parents[var]: ax.annotate(var.name, par.position, xytext=var.position, arrowprops={'arrowstyle':'<-'},bbox=bbox, ha='center') else: x,y = var.position plt.text(x,y,var.name,bbox=bbox,ha='center') from probVariables import Variable from probFactors import Prob, LogisticRegression, NoisyOR boolean = [False, True] A = Variable("A", boolean, position=(0,0.8)) B = Variable("B", boolean, position=(0.333,0.6)) C = Variable("C", boolean, position=(0.666,0.4)) D = Variable("D", boolean, position=(1,0.2)) f_a = Prob(A,[],[0.4,0.6]) f_b = Prob(B,[A],[[0.9,0.1],[0.2,0.8]]) f_c = Prob(C,[B],[[0.6,0.4],[0.3,0.7]]) f_d = Prob(D,[C],[[0.1,0.9],[0.75,0.25]]) bn_4ch = BeliefNetwork("4-chain", {A,B,C,D}, {f_a,f_b,f_c,f_d}) # Belief network report-of-leaving example (Example 8.15 shown in Figure 8.3) of # Poole and Mackworth, Artificial Intelligence, 2017 http://artint.info Alarm = Variable("Alarm", boolean, position=(0.366,0.633)) Fire = Variable("Fire", boolean, position=(0.633,0.9)) Leaving = Variable("Leaving", boolean, position=(0.366,0.366)) Report = Variable("Report", boolean, position=(0.366,0.1)) Smoke = Variable("Smoke", boolean, position=(0.9,0.633)) Tamper = Variable("Tamper", boolean, position=(0.1,0.9)) f_ta = Prob(Tamper,[],[0.98,0.02]) f_fi = Prob(Fire,[],[0.99,0.01]) f_sm = Prob(Smoke,[Fire],[[0.99,0.01],[0.1,0.9]]) f_al = Prob(Alarm,[Fire,Tamper],[[[0.9999, 0.0001], [0.15, 0.85]], [[0.01, 0.99], [0.5, 0.5]]]) f_lv = Prob(Leaving,[Alarm],[[0.999, 0.001], [0.12, 0.88]]) f_re = Prob(Report,[Leaving],[[0.99, 0.01], [0.25, 0.75]]) bn_report = BeliefNetwork("Report-of-leaving", {Tamper,Fire,Smoke,Alarm,Leaving,Report}, {f_ta,f_fi,f_sm,f_al,f_lv,f_re}) Season = Variable("Season", ["summer","winter"], position=(0.5,0.9)) Sprinkler = Variable("Sprinkler", ["on","off"], position=(0.9,0.6)) Rained = Variable("Rained", boolean, position=(0.1,0.6)) Grass_wet = Variable("Grass wet", boolean, position=(0.5,0.3)) Grass_shiny = Variable("Grass shiny", boolean, position=(0.1,0)) Shoes_wet = Variable("Shoes wet", boolean, position=(0.9,0)) f_season = Prob(Season,[],{'summer':0.5, 'winter':0.5}) f_sprinkler = Prob(Sprinkler,[Season],{'summer':{'on':0.9,'off':0.1}, 'winter':{'on':0.01,'off':0.99}}) f_rained = Prob(Rained,[Season],{'summer':[0.9,0.1], 'winter': [0.2,0.8]}) f_wet = Prob(Grass_wet,[Sprinkler,Rained], {'on': [[0.1,0.9],[0.01,0.99]], 'off':[[0.99,0.01],[0.3,0.7]]}) f_shiny = Prob(Grass_shiny, [Grass_wet], [[0.95,0.05], [0.3,0.7]]) f_shoes = Prob(Shoes_wet, [Grass_wet], [[0.98,0.02], [0.35,0.65]]) bn_sprinkler = BeliefNetwork("Pearl's Sprinkler Example", {Season, Sprinkler, Rained, Grass_wet, Grass_shiny, Shoes_wet}, {f_season, f_sprinkler, f_rained, f_wet, f_shiny, f_shoes}) bn_sprinkler_soff = BeliefNetwork("Pearl's Sprinkler Example (do(Sprinkler=off))", {Season, Sprinkler, Rained, Grass_wet, Grass_shiny, Shoes_wet}, {f_season, f_rained, f_wet, f_shiny, f_shoes, Prob(Sprinkler,[],{'on':0,'off':1})}) Cough = Variable("Cough", boolean, (0.1,0.1)) Fever = Variable("Fever", boolean, (0.5,0.1)) Sneeze = Variable("Sneeze", boolean, (0.9,0.1)) Cold = Variable("Cold",boolean, (0.1,0.9)) Flu = Variable("Flu",boolean, (0.5,0.9)) Covid = Variable("Covid",boolean, (0.9,0.9)) p_cold_no = Prob(Cold,[],[0.9,0.1]) p_flu_no = Prob(Flu,[],[0.95,0.05]) p_covid_no = Prob(Covid,[],[0.99,0.01]) p_cough_no = NoisyOR(Cough, [Cold,Flu,Covid], [0.1, 0.3, 0.2, 0.7]) p_fever_no = NoisyOR(Fever, [ Flu,Covid], [0.01, 0.6, 0.7]) p_sneeze_no = NoisyOR(Sneeze, [Cold,Flu ], [0.05, 0.5, 0.2 ]) bn_no1 = BeliefNetwork("Bipartite Diagnostic Network (noisy-or)", {Cough, Fever, Sneeze, Cold, Flu, Covid}, {p_cold_no, p_flu_no, p_covid_no, p_cough_no, p_fever_no, p_sneeze_no}) # to see the conditional probability of Noisy-or do: # print(p_cough_no.to_table()) # example from box "Noisy-or compared to logistic regression" # X = Variable("X",boolean) # w0 = 0.01 # print(NoisyOR(X,[A,B,C,D],[w0, 1-(1-0.05)/(1-w0), 1-(1-0.1)/(1-w0), 1-(1-0.2)/(1-w0), 1-(1-0.2)/(1-w0), ]).to_table(given={X:True})) p_cold_lr = Prob(Cold,[],[0.9,0.1]) p_flu_lr = Prob(Flu,[],[0.95,0.05]) p_covid_lr = Prob(Covid,[],[0.99,0.01]) p_cough_lr = LogisticRegression(Cough, [Cold,Flu,Covid], [-2.2, 1.67, 1.26, 3.19]) p_fever_lr = LogisticRegression(Fever, [ Flu,Covid], [-4.6, 5.02, 5.46]) p_sneeze_lr = LogisticRegression(Sneeze, [Cold,Flu ], [-2.94, 3.04, 1.79 ]) bn_lr1 = BeliefNetwork("Bipartite Diagnostic Network - logistic regression", {Cough, Fever, Sneeze, Cold, Flu, Covid}, {p_cold_lr, p_flu_lr, p_covid_lr, p_cough_lr, p_fever_lr, p_sneeze_lr}) # to see the conditional probability of Noisy-or do: #print(p_cough_lr.to_table()) # example from box "Noisy-or compared to logistic regression" # from learnLinear import sigmoid, logit # w0=logit(0.01) # X = Variable("X",boolean) # print(LogisticRegression(X,[A,B,C,D],[w0, logit(0.05)-w0, logit(0.1)-w0, logit(0.2)-w0, logit(0.2)-w0]).to_table(given={X:True})) # try to predict what would happen (and then test) if we had # w0=logit(0.01) from display import Displayable class InferenceMethod(Displayable): """The abstract class of graphical model inference methods""" method_name = "unnamed" # each method should have a method name def __init__(self,gm=None): self.gm = gm def query(self, qvar, obs={}): """returns a {value:prob} dictionary for the query variable""" raise NotImplementedError("InferenceMethod query") # abstract method def testIM(self, threshold=0.0000000001): solver = self(bn_4ch) res = solver.query(B,{D:True}) correct_answer = 0.429632380245 assert correct_answer-threshold < res[True] < correct_answer+threshold, \ f"value {res[True]} not in desired range for {self.method_name}" print(f"Unit test passed for {self.method_name}.")