Added minimal-consistent-det (aimacode#610)

Chipe1 · norvig · commit 790213a1f3c2 · 2017-08-07T22:36:52.000-07:00
diff --git a/knowledge.py b/knowledge.py
@@ -3,6 +3,7 @@
 from random import shuffle
 from utils import powerset
 from collections import defaultdict
+from itertools import combinations
 
 # ______________________________________________________________________________
 
@@ -205,6 +206,29 @@ def build_h_combinations(hypotheses):
 # ______________________________________________________________________________
 
 
+def minimal_consistent_det(E, A):
+    n = len(A)
+
+    for i in range(n + 1):
+        for A_i in combinations(A, i):
+            if consistent_det(A_i, E):
+                return set(A_i)
+
+
+def consistent_det(A, E):
+    H = {}
+
+    for e in E:
+        attr_values = tuple(e[attr] for attr in A)
+        if attr_values in H and H[attr_values] != e['GOAL']:
+            return False
+        H[attr_values] = e['GOAL']
+
+    return True
+
+# ______________________________________________________________________________
+
+
 def check_all_consistency(examples, h):
     """Check for the consistency of all examples under h"""
     for e in examples:
diff --git a/tests/test_knowledge.py b/tests/test_knowledge.py
@@ -49,6 +49,14 @@ def test_version_space_learning():
     assert [{'Pizza': 'Yes'}] in V
 
 
+def test_minimal_consistent_det():
+    assert minimal_consistent_det(party, {'Pizza', 'Soda'}) == {'Pizza'}
+    assert minimal_consistent_det(party[:2], {'Pizza', 'Soda'}) == set()
+    assert minimal_consistent_det(animals_umbrellas, {'Species', 'Rain', 'Coat'}) == {'Species', 'Rain', 'Coat'}
+    assert minimal_consistent_det(conductance, {'Mass', 'Temp', 'Material', 'Size'}) == {'Temp', 'Material'}
+    assert minimal_consistent_det(conductance, {'Mass', 'Temp', 'Size'}) == {'Mass', 'Temp', 'Size'}
+
+
 party = [
     {'Pizza': 'Yes', 'Soda': 'No', 'GOAL': True},
     {'Pizza': 'Yes', 'Soda': 'Yes', 'GOAL': True},
@@ -65,6 +73,18 @@ def test_version_space_learning():
     {'Species': 'Cat', 'Rain': 'No', 'Coat': 'Yes', 'GOAL': True}
 ]
 
+conductance = [
+    {'Sample': 'S1', 'Mass': 12, 'Temp': 26, 'Material': 'Cu', 'Size': 3, 'GOAL': 0.59},
+    {'Sample': 'S1', 'Mass': 12, 'Temp': 100, 'Material': 'Cu', 'Size': 3, 'GOAL': 0.57},
+    {'Sample': 'S2', 'Mass': 24, 'Temp': 26, 'Material': 'Cu', 'Size': 6, 'GOAL': 0.59},
+    {'Sample': 'S3', 'Mass': 12, 'Temp': 26, 'Material': 'Pb', 'Size': 2, 'GOAL': 0.05},
+    {'Sample': 'S3', 'Mass': 12, 'Temp': 100, 'Material': 'Pb', 'Size': 2, 'GOAL': 0.04},
+    {'Sample': 'S4', 'Mass': 18, 'Temp': 100, 'Material': 'Pb', 'Size': 3, 'GOAL': 0.04},
+    {'Sample': 'S4', 'Mass': 18, 'Temp': 100, 'Material': 'Pb', 'Size': 3, 'GOAL': 0.04},
+    {'Sample': 'S5', 'Mass': 24, 'Temp': 100, 'Material': 'Pb', 'Size': 4, 'GOAL': 0.04},
+    {'Sample': 'S6', 'Mass': 36, 'Temp': 26, 'Material': 'Pb', 'Size': 6, 'GOAL': 0.05},
+]
+
 def r_example(Alt, Bar, Fri, Hun, Pat, Price, Rain, Res, Type, Est, GOAL):
     return {'Alt': Alt, 'Bar': Bar, 'Fri': Fri, 'Hun': Hun, 'Pat': Pat,
             'Price': Price, 'Rain': Rain, 'Res': Res, 'Type': Type, 'Est': Est,
