def solve_safety_inc_bwd(self, hts, prop, k, assert_property=False, generalize=None):
solver = self.solver.copy("inc_bwd")
self._reset_assertions(solver)
has_next = TS.has_next(prop)
if has_next:
prop = TS.to_prev(prop)
init = hts.single_init()
trans = hts.single_trans()
invar = hts.single_invar()
formula = self.at_ptime(And(Not(prop), invar), -1)
Logger.log("Add not property at time %d"%0, 2)
self._add_assertion(solver, formula)
skip_push = False
constraints = TRUE()
models = 0
t = 0
k_min = 1 if has_next else 0
while (t < k+1):
if not skip_push:
self._push(solver)
skip_push = False
if not skip_push:
pinit = self.at_ptime(init, t-1)
Logger.log("Add init at time %d"%t, 2)
self._add_assertion(solver, pinit)
if constraints != TRUE():
for j in range(t+1):
self._add_assertion(solver, self.at_ptime(constraints, j-1), "Addditional Constraints")
if self.preferred is not None:
try:
for (var, val) in self.preferred:
solver.solver.set_preferred_var(TS.get_timed(var, t), val)
except:
Logger.warning("Current solver does not support preferred variables")
self.preferred = None
if (t >= k_min) and self._solve(solver):
Logger.log("Counterexample found with k=%s"%(t), 1)
model = self._get_model(solver)
models += 1
if models > 20:
Logger.msg("R", 0, not(Logger.level(1)))
self._reset_solver(solver)
models = 0
if generalize is not None:
constr, res = generalize(model, t)
if res:
return (t, model)
constraints = And(constraints, Not(constr))
skip_push = True
continue
else:
return (t, model)
else:
Logger.log("No counterexample found with k=%s"%(t), 1)
Logger.msg(".", 0, not(Logger.level(1)))
self._pop(solver)
skip_push = False
trans_t = self.unroll(trans, invar, t, t+1)
self._add_assertion(solver, trans_t)
if assert_property and t > 0:
prop_t = self.unroll(TRUE(), prop, t-1, t)
self._add_assertion(solver, prop_t)
Logger.log("Add property at time %d"%t, 2)
t += 1
return (t-1, None)
def Prev(self, x):
return TS.to_prev(x)
