def test_conflict_analysis_v2(self):
x, y, z = self.new_lit(), self.new_lit(), self.new_lit()
a = Assignment(self.__mem, x, y, z)
a.make_decision(z)
a.make_implication(x, self.new_clause(x.negated, z))
a.make_implication(y, self.new_clause(y.negated, z))
conflict = self.new_clause(x, y)
self.assertTrue(conflict.is_conflict(a))
self.assertEqual([z], a.analyze_conflict(conflict))
def test_conflict_analysis_v3(self):
u, v, x, y = self.new_lit(), self.new_lit(), self.new_lit(
), self.new_lit()
a = Assignment(self.__mem, u, v, x, y)
a.make_decision(v)
a.make_decision(y)
a.make_implication(x, self.new_clause(x.negated, v, y))
a.make_implication(u, self.new_clause(u.negated, v, x))
conflict = self.new_clause(u)
self.assertTrue(conflict.is_conflict(a))
self.assertEqual([u], a.analyze_conflict(conflict))
def test_conflict_analysis_v4(self):
x1, x2, x3 = self.new_lit(), self.new_lit(), self.new_lit()
x4, x5, x6 = self.new_lit(), self.new_lit(), self.new_lit()
x7, x8, x9 = self.new_lit(), self.new_lit(), self.new_lit()
a = Assignment(self.__mem, x1, x2, x3, x4, x5, x6, x7, x8, x9)
a.make_decision(x1)
a.make_implication(x5, self.new_clause(x5.negated, x1))
a.make_decision(x6)
a.make_decision(x9)
a.make_implication(x8, self.new_clause(x8.negated, x9))
a.make_implication(x7, self.new_clause(x7.negated, x6, x9, x8))
a.make_implication(x4, self.new_clause(x4.negated, x7))
a.make_implication(x2, self.new_clause(x2.negated, x4, x7))
a.make_implication(x3, self.new_clause(x3.negated, x4, x5))
conflict = self.new_clause(x1, x2, x3)
self.assertTrue(conflict.is_conflict(a))
self.assertEqual([x7, x5, x1], a.analyze_conflict(conflict))
def __dpll(self, xs: 'List[Literal]', f: 'Set[Clause]') -> 'Status':
a = Assignment(self.__mem, *xs)
while True:
while True:
clause = a.get_suspicious_clause()
if clause is None:
break
if clause.is_conflict(a):
literals = a.analyze_conflict(clause)
x = literals[0]
if len(literals) == 1:
if x.link == a.sentinel:
return Status.UNSAT
backtrack_lit = a.sentinel.link
if backtrack_lit != a.sentinel:
a.backtrack(backtrack_lit)
else:
y = literals[1]
backtrack_lit = y.link if y.antecedent is None else y.link.link
assert backtrack_lit != a.sentinel
a.backtrack(backtrack_lit)
asserting_clause = self.new_clause(*literals)
self.assertEqual(x, asserting_clause.derive(a))
a.make_implication(x.negated, asserting_clause)
else:
z = clause.derive(a)
if z is not None:
a.make_implication(z.negated, clause)
if a.border.value == len(xs) + 1:
break
d = a.literals[a.border.value]
a.make_decision(d.negated)
self.assertTrue(all((a[x] is not None) for x in xs))
for c in f:
self.assertTrue(any((a[x.negated] is True) for x in c.literals))
return Status.SAT
def test_dpll_steps(self):
x1 = self.new_lit()
x2 = self.new_lit()
x3 = self.new_lit()
x4 = self.new_lit()
x5 = self.new_lit()
x6 = self.new_lit()
a = Assignment(self.__mem, x1, x2, x3, x4, x5, x6)
c1 = self.new_clause(x1.negated, x2)
c2 = self.new_clause(x3.negated, x4)
c3 = self.new_clause(x5.negated, x6.negated)
c4 = self.new_clause(x6, x5.negated, x2.negated)
# DECIDE
a.make_decision(x1.negated)
# UNIT PROPAGATION
self.assertEqual(c1, a.get_suspicious_clause())
self.assertIsNone(a.get_suspicious_clause())
self.assertEqual(x2, c1.derive(a))
a.make_implication(x2.negated, c1)
# DECIDE
a.make_decision(x3.negated)
# UNIT PROPAGATION
self.assertEqual(c2, a.get_suspicious_clause())
self.assertIsNone(a.get_suspicious_clause())
self.assertEqual(x4, c2.derive(a))
a.make_implication(x4.negated, c2)
# DECIDE
a.make_decision(x5.negated)
# UNIT PROPAGATION
self.assertEqual(c3, a.get_suspicious_clause())
self.assertEqual(x6.negated, c3.derive(a))
a.make_implication(x6, c3)
# BACKJUMP & LEARN
self.assertEqual(c4, a.get_suspicious_clause())
self.assertTrue(c4.is_conflict(a))
analysis = a.analyze_conflict(c4)
self.assertEqual([x5.negated, x2.negated], analysis)
c5 = self.new_clause(*analysis)
self.assertEqual(x3.negated, analysis[1].link.link)
a.backtrack(x3.negated)
self.assertEqual(x5.negated, c5.derive(a))
a.make_implication(x5, c5)
# DECIDE
a.make_decision(x3.negated)
# UNIT PROPAGATION
self.assertEqual(c2, a.get_suspicious_clause())
self.assertIsNone(a.get_suspicious_clause())
self.assertEqual(x4, c2.derive(a))
a.make_implication(x4.negated, c2)
# DECIDE
a.make_decision(x6.negated)
# verdict: SAT
while True:
c = a.get_suspicious_clause()
if c is None:
break
self.assertFalse(c.is_conflict(a))
self.assertIsNone(c.derive(a))