def resolve_units(self,lit,units,gen,allow_unit_diseqs):
for lit_idx in list(units): # copy the list in case it changes
lit2 = lit_rep(self.unit_queue[lit_idx])
match, subs, eqs = mgu_eq(lit.atom, lit2.atom)
# print "lit: %s" % lit
if match and (self.allow_eqs(lit,eqs,True) or (allow_unit_diseqs and len(eqs) == 1 and keep_atom(eqs[0]))):
new_cl = [Literal(0,eq) for eq in eqs]
if not self.subsumed_by_used_lit(lit,lit2,new_cl):
if verbose():
print "units resolve! %s,%s -> %s" % (lit,lit2,new_cl)
new_gen = max(gen+1,self.unit_queue_gen[lit_idx])
self.add_clause(new_cl,new_gen)
if self.unsat:
return
def propagate_lit(self,lit,gen=0,specs = None):
"""
Perform unit resolution using a literal.
>>> r = UnitRes(to_clauses("[[a(),b()]]"))
>>> r.propagate_lit(to_literal('~a()'))
>>> r.unit_queue
[b()]
>>> r.watching
[{}, {'a': [], 'b': []}]
>>> r.subsumed
[0]
>>> r.clauses
[[a(), b()]]
"""
# print self.index
if self.equational_theory != None and is_ground_equality_lit(lit):
self.propagate_equality(lit,gen)
return
# if lit.atom.relname == '=' and lit.polarity == 0:
# return
lits = [lit,Literal(lit.polarity,Atom('=',[lit.atom.args[1],lit.atom.args[0]]))] if lit.atom.relname == '=' else [lit]
for lit in lits:
keep = keep_lit(lit)
indices = list(find_unifying(self.index,Literal(1 - lit.polarity,lit.atom))) # save this in cas index changes
lit = lit_rep(canonize_literal_unique(lit))
for index in indices:
wl = index[1]
# print "%s -- %s" % (lit,wl)
for i,j in list(wl): # copy the list in case we modify it
cl = self.clauses[i]
# print "cl: %s lit: %s" % (cl,lit)
lit2 = lit_rep(cl[j])
if lit2.polarity != 1-lit.polarity or lit2.atom.relname != lit.atom.relname:
print "!!! %s %s %s %s %s" % (i,j,lit,lit2,cl)
exit(1)
if is_equality_lit(lit2) and all(isinstance(t,Variable) for t in lit2.atom.args):
continue
match, subs, eqs = mgu_eq(lit.atom, lit2.atom)
# print "lit: %s" % lit
if match and self.allow_eqs(lit,eqs,False,cl):
if atom_subsume(lit.atom,lit2.atom):
self.deindex(i)
self.subsumed.append(i)
# print "lit: %s" % lit
new_cl = [substitute_lit(lit1, subs) for k,lit1 in enumerate(cl) if k != j] + [Literal(0,eq) for eq in eqs]
if not new_specialization and not (specs == None):
if verbose():
print "using specs: %s" % specs
new_cl = substitute_constants_clause(new_cl,specs)
new_cl = simplify_clause(new_cl)
if not is_tautology(new_cl) and not self.subsumed_by_used_lit(lit,cl,new_cl):
if verbose():
print "%s,%s -> %s" % (lit,cl,new_cl)
new_gen = max(gen+1,self.clauses_gen[i])
self.add_clause(new_cl,new_gen)
if self.unsat:
return
if keep:
self.resolve_units(lit,index[0],gen,False) # have to unify against units too!
if self.unsat:
return
# if we are not keeping this unit as a consequence,
# resolve it against all of the the units that might match
# under equality, so that we can infer disequalities
if keep == False:
others = [x for x in self.unit_term_index[lit.atom.relname] if self.unit_queue[x].polarity != lit.polarity]
self.resolve_units(lit,others,gen,True) #
if self.unsat:
return
