def _resolve(self):
"""
:return:
"""
start_time = time.time()
i = 0
checked = list()
while i < len(self._cnf_list):
if (time.time() - start_time) > self.proof_timeout:
raise exceptions.TimeoutException('Proof timeout reached')
j = i + 1
while j < len(self._cnf_list):
if [i, j] in checked:
j += 1
continue
checked.append([i, j])
have_resolve = False
for k in range(len(self._cnf_list[i])):
atomic = self._cnf_list[i][k]
negation = util.negate_formula(atomic)
try:
resolve = Prover._get_index(self._cnf_list[j],
negation)
cnf_list1 = deepcopy(self._cnf_list[i])
cnf_list2 = deepcopy(self._cnf_list[j])
if resolve[1] >= 1:
Prover._remove_herbrand(resolve, cnf_list1,
cnf_list2, k)
ind = resolve[0]
new_cnf = cnf_list1[:k]
new_cnf += cnf_list1[(k + 1):]
for cnf in cnf_list2[:ind]:
if cnf not in new_cnf:
new_cnf.append(cnf)
for cnf in cnf_list2[(ind + 1):]:
if cnf not in new_cnf:
new_cnf.append(cnf)
new_cnf.sort()
if len(new_cnf) == 0:
self._cnf_list.append([])
self.parents.append([i, j])
return True, time.time() - start_time
if not util.is_tautology(new_cnf) and \
new_cnf not in self._cnf_list:
have_resolve = True
self._cnf_list.append(new_cnf)
self.parents.append([i, j])
checked.append([i, len(self._cnf_list) - 1])
checked.append([j, len(self._cnf_list) - 1])
except ValueError:
pass
if have_resolve is True:
i = -1
break
j += 1
i += 1
return False, time.time() - start_time
def _tautology_elimination(self):
"""
Remove any CNF tautologies
:return:
"""
i = 0
while i < len(self._cnf_list):
cnf = self._cnf_list[i]
if util.is_tautology(cnf):
self._cnf_list.pop(i)
i -= 1
i += 1
def test_is_tautology_negative(self):
cnf = list()
cnf.append(Symbol("a"))
cnf.append(Symbol("b"))
is_taut = util.is_tautology(cnf)
self.assertFalse(is_taut)
def test_is_tautology_bad_input(self):
self.assertFalse(util.is_tautology("a"))
self.assertFalse(util.is_tautology([Symbol("a")]))
def test_is_tautology(self):
cnf = list()
cnf.append(Symbol("a"))
cnf.append(Not(Symbol("a")))
is_taut = util.is_tautology(cnf)
self.assertTrue(is_taut)