def test_variable_ordering():
a = V()
b = V()
c = V()
c1 = C([a, b])
c2 = C([N(a), c])
c3 = C([N(c), a])
f = F([c1, c2, c3], [a,b,c])
assert f.variables == [a, c,b]
def test_unit_propagation2():
a = V()
b = V()
c = C([N(a),b])
assignment = {a:True}
c.unit_propagation(assignment)
c = C([N(a),N(b)])
assignment = {b:True}
c.unit_propagation(assignment)
assert assignment[a] == False
def test_variable_freqs():
a = V()
b = V()
c = V()
c1 = C([a, b])
c2 = C([N(a), c])
c3 = C([N(c), a])
f = F([c1, c2, c3], [a,b,c])
freqs = f.variable_freqs()
assert freqs[a] == 3
assert freqs[c] == 2
assert freqs[b] == 1
def test_multiple_clauses():
a = V()
b = V()
c = V()
cs = [C([a, N(b)]), C([N(a), c])]
f = F(cs, [a, b, c])
assignment = {}
assert f.is_satisfied(assignment) == False
assignment = {a: True, b:True, c:True}
assert f.is_satisfied(assignment) == True
assignment = {a: True, b:True, c:False}
assert f.is_satisfied(assignment) == False
def test_is_conflicting():
a = V()
b = V()
c1 = C([a, b])
c2 = C([N(a), b])
f = F([c1], [a,b])
assignment={a:False, b:False}
assert f.is_satisfied(assignment) == False
assert f.is_conflicting(assignment) == True
f = F([c1], [a,b])
assignment={a:True, b:False}
assert f.is_satisfied(assignment) == True
assert f.is_conflicting(assignment) == False
f = F([c2], [a,b])
assignment={a:False, b:False}
assert f.is_satisfied(assignment) == True
assert f.is_conflicting(assignment) == False
f = F([c2], [a,b])
assignment={a:True, b:False}
assert f.is_satisfied(assignment) == False
assert f.is_conflicting(assignment) == True
f = F([c2], [a,b])
assignment={a:True}
assert f.is_satisfied(assignment) == False
assert f.is_conflicting(assignment) == False
def test_dpll():
a = V()
b = V()
c = V()
c1 = C([a, b])
c2 = C([N(a), c])
f = F([c1, c2], [a,b,c])
assignment = f.dpll()
assert f.is_satisfied(assignment) == True
def test_satisfied_negation():
a = V()
b = V()
c = C([a, N(b)])
f = F([c], [a, b])
assignment= {b: True}
assert f.is_satisfied(assignment) == False
assignment[b] = False
assert f.is_satisfied(assignment) == True
assignment[a] = False
assignment[b] = False
assert f.is_satisfied(assignment) == True
def test_choose_free_variable():
a = V()
b = V()
c = V()
c1 = C([a, b])
c2 = C([N(a), c])
f = F([c1, c2], [a, b, c])
assert f.choose_free_variable({}) in [a, b, c]
f = F([c1, c2], [a, b, c])
assignment={a:True}
assert f.choose_free_variable(assignment) in [b, c]
f = F([c1, c2], [a, b, c])
assignment={a:True, c:False}
assert f.choose_free_variable(assignment) is b
f = F([c1, c2], [a, b, c])
assignment={a:True, c:False, b:True}
py.test.raises(Exception, f, f.choose_free_variable, assignment)