def forbid_gndatom(self, atom, truth=True):
'''
Adds a unary constraint that prohibits the given ground atom
being true.
'''
atomidx = atom if type(atom) is int else (self.mrf.gndatom(atom).idx if type(atom) is str else atom.idx)
varidx = self.atom2var[atomidx]
variable = self.variables[varidx]
evidence = list(self.mrf.evidence)
evidence[atomidx] = {True: 1, False: 0}[truth]
c = Constraint((varidx,))
for _, value in variable.itervalues(evidence):
validx = self.val2idx[varidx][value]
c.tuple((validx,), self.wcsp.top)
self.wcsp.constraint(c)
def generate_constraint(self, wf):
'''
Generates and adds a constraint from a given weighted formula.
'''
varindices = tuple(map(lambda x: self.atom2var[x], wf.gndatom_indices()))
# collect the constraint tuples
cost2assignments = self._gather_constraint_tuples(varindices, wf)
if cost2assignments is None:
return
defcost = max(cost2assignments, key=lambda x: infty if cost2assignments[x] == 'else' else len(cost2assignments[x]))
del cost2assignments[defcost] # remove the default cost values
constraint = Constraint(varindices, defcost=defcost)
for cost, tuples in cost2assignments.iteritems():
for t in tuples:
constraint.tuple(t, cost)
self.wcsp.constraint(constraint)