def _search_solver_helper(self, sent, symbols):
m = sent.implicit_model()
unassigned_symbols = sorted(symbols - m.keys()) # TODO: different orders
if len(unassigned_symbols) == 0:
if sent.check_model(m):
return m
else:
return None
else:
next_symbol = unassigned_symbols[0]
negative_unit_clause = Clause([Literal(next_symbol, polarity=False)])
closure = limited_unit_resolution_closure(negative_unit_clause,
sent.clauses)
if cnf.c('FALSE') not in closure:
sat_if_false = self._search_solver_helper(Cnf(closure), symbols)
if sat_if_false != None: # early termination if already satisfied
return sat_if_false
positive_unit_clause = Clause([Literal(next_symbol, polarity=True)])
closure = limited_unit_resolution_closure(positive_unit_clause,
sent.clauses)
if cnf.c('FALSE') not in closure:
sat_if_true = self._search_solver_helper(Cnf(closure), symbols)
return sat_if_true
else:
return None
def _search_solver_helper(self, sent, symbols):
def assign(model_so_far, symbol, bool_assignment):
if bool_assignment:
assignment = 1
else:
assignment = -1
return {**model_so_far, symbol: assignment}
self.visited += 1
if sent is None:
return None
m = sent.current_assignment()
unassigned_symbols = sorted(symbols -
m.keys()) # TODO: different orders
if len(unassigned_symbols) == 0:
if sent.check_term(m):
return m
else:
return None
else:
next_symbol = unassigned_symbols[0]
positive_unit_clause = Clause([Literal(next_symbol, neg=False)])
new_clauses = unit_resolution(positive_unit_clause, sent)
sat_if_true = self._search_solver_helper(new_clauses, symbols)
if sat_if_true != None: # early termination if already satisfied
return sat_if_true
negative_unit_clause = Clause([Literal(next_symbol, neg=True)])
new_clauses = unit_resolution(negative_unit_clause, sent)
sat_if_false = self._search_solver_helper(new_clauses, symbols)
return sat_if_false
def _max_one_color(self, cnf):
for country in self.G.nodes():
for color_combos in combinations(self.colors, 2):
clause = Clause()
clause.add_literal( -self._convert_to_literal(country, color_combos[0]) )
clause.add_literal( -self._convert_to_literal(country, color_combos[1]) )
clause.end()
cnf.add_clause(clause)
def _at_leat_one_color(self, cnf):
for country in self.G.nodes():
clause = Clause()
for color in self.colors:
literal = self._convert_to_literal(country, color)
clause.add_literal(literal)
clause.end()
cnf.add_clause(clause)
def generate_random_clause(k, N):
variables = choose(N, k)
literals = []
for var in variables:
neg = random.choice([True, False])
literal = Literal(str(var), neg)
literals.append(literal)
return Clause(literals)
def _max_one_color(self, cnf):
for country in self.G.nodes():
for color_combos in combinations(self.colors, 2):
clause = Clause()
clause.add_literal(
-self._convert_to_literal(country, color_combos[0]))
clause.add_literal(
-self._convert_to_literal(country, color_combos[1]))
clause.end()
cnf.add_clause(clause)
def _different_colors(self, cnf):
for country in self.G.nodes():
for neighbor in self.G.neighbors(country):
for color in self.colors:
clause = Clause()
clause.add_literal(
-self._convert_to_literal(country, color))
clause.add_literal(
-self._convert_to_literal(neighbor, color))
clause.end()
cnf.add_clause(clause)
def _search_solver_helper(self, sent, symbols):
m = sent.implicit_model()
unassigned_symbols = sorted(symbols - m.keys())
if len(unassigned_symbols) == 0:
if sent.check_model(m):
return m, [m]
else:
return None, [m]
else:
next_symbol = unassigned_symbols[0]
negative_unit_clause = Clause([Literal(next_symbol, polarity=False)])
sent_if_false = Cnf(sent.clauses | { negative_unit_clause })
sat_if_false, models_if_false = self._search_solver_helper(sent_if_false, symbols)
if sat_if_false != None: # early termination if already satisfied
return sat_if_false, models_if_false
positive_unit_clause = Clause([Literal(next_symbol, polarity=True)])
sent_if_true = Cnf(sent.clauses | { positive_unit_clause })
sat_if_true, models_if_true = self._search_solver_helper(sent_if_true, symbols)
return sat_if_true, models_if_false + models_if_true
def _different_colors(self, cnf):
for country in self.G.nodes():
for neighbor in self.G.neighbors(country):
for color in self.colors:
clause = Clause()
clause.add_literal( -self._convert_to_literal(country, color) )
clause.add_literal( -self._convert_to_literal(neighbor, color) )
clause.end()
cnf.add_clause(clause)
def _at_leat_one_color(self, cnf):
for country in self.G.nodes():
clause = Clause()
for color in self.colors:
literal = self._convert_to_literal(country, color)
clause.add_literal(literal)
clause.end()
cnf.add_clause(clause)
