def test_polarity_shuffle_vs_flip(self) :
cnf = CNF([[(True,'x'),(True,'y'),(False,'z')]])
variable_permutation = list(cnf.variables())
clause_permutation = range(len(cnf))
polarity_flip = [-1]*len(variable_permutation)
shuffled = Shuffle(cnf, variable_permutation, clause_permutation, polarity_flip)
flipped = FlipPolarity(cnf)
self.assertCnfEqual(flipped,shuffled)
def test_polarity_shuffle_vs_flip(self):
cnf = CNF([[(True, 'x'), (True, 'y'), (False, 'z')]])
variable_permutation = list(cnf.variables())
clause_permutation = list(range(len(cnf)))
polarity_flip = [-1] * len(variable_permutation)
shuffled = Shuffle(cnf, variable_permutation, clause_permutation,
polarity_flip)
flipped = FlipPolarity(cnf)
self.assertCnfEqual(flipped, shuffled)
def reshuffle(cnf,
variable_permutation=None,
clause_permutation=None,
polarity_flip=None):
""" Reshuffle the given cnf. Returns a formula logically
equivalent to the input with the following transformations
applied in order:
1. Polarity flips. polarity_flip is a {-1,1}^n vector. If the i-th
entry is -1, all the literals with the i-th variable change its
sign.
2. Variable permutations. variable_permutation is a permutation of
[vars(cnf)]. All the literals with the old i-th variable are
replaced with the new i-th variable.
3. Clause permutations. clause_permutation is a permutation of
[0..m-1]. The resulting clauses are reordered according to the
permutation.
"""
# empty cnf
out = CNF(header='')
out.header = "Reshuffling of:\n\n" + cnf.header
variables = list(cnf.variables())
N = len(variables)
M = len(cnf)
# variable permutation
if variable_permutation == None:
variable_permutation = variables
random.shuffle(variable_permutation)
else:
assert len(variable_permutation) == N
# polarity flip
if polarity_flip == None:
polarity_flip = [random.choice([-1, 1]) for x in xrange(N)]
else:
assert len(polarity_flip) == N
#
# substitution of variables
#
for v in variable_permutation:
out.add_variable(v)
substitution = [None] * (2 * N + 1)
reverse_idx = dict([(v, i) for (i, v) in enumerate(out.variables(), 1)])
polarity_flip = [None] + polarity_flip
for i, v in enumerate(cnf.variables(), 1):
substitution[i] = polarity_flip[i] * reverse_idx[v]
substitution[-i] = -substitution[i]
#
# permutation of clauses
#
if clause_permutation == None:
clause_permutation = range(M)
random.shuffle(clause_permutation)
# load clauses
out._clauses = [None] * M
for (old, new) in enumerate(clause_permutation):
out._clauses[new] = tuple(substitution[l] for l in cnf._clauses[old])
# return the formula
assert out._check_coherence(force=True)
return out
def reshuffle(cnf,
variable_permutation=None,
clause_permutation=None,
polarity_flip=None
):
""" Reshuffle the given cnf. Returns a formula logically
equivalent to the input with the following transformations
applied in order:
1. Polarity flips. polarity_flip is a {-1,1}^n vector. If the i-th
entry is -1, all the literals with the i-th variable change its
sign.
2. Variable permutations. variable_permutation is a permutation of
[vars(cnf)]. All the literals with the old i-th variable are
replaced with the new i-th variable.
3. Clause permutations. clause_permutation is a permutation of
[0..m-1]. The resulting clauses are reordered according to the
permutation.
"""
# empty cnf
out=CNF(header='')
out.header="Reshuffling of:\n\n"+cnf.header
variables=list(cnf.variables())
N=len(variables)
M=len(cnf)
# variable permutation
if variable_permutation==None:
variable_permutation=variables
random.shuffle(variable_permutation)
else:
assert len(variable_permutation)==N
# polarity flip
if polarity_flip==None:
polarity_flip=[random.choice([-1,1]) for x in xrange(N)]
else:
assert len(polarity_flip)==N
#
# substitution of variables
#
for v in variable_permutation:
out.add_variable(v)
substitution=[None]*(2*N+1)
reverse_idx=dict([(v,i) for (i,v) in enumerate(out.variables(),1)])
polarity_flip = [None]+polarity_flip
for i,v in enumerate(cnf.variables(),1):
substitution[i]= polarity_flip[i]*reverse_idx[v]
substitution[-i]= -substitution[i]
#
# permutation of clauses
#
if clause_permutation==None:
clause_permutation=range(M)
random.shuffle(clause_permutation)
# load clauses
out._clauses = [None]*M
for (old,new) in enumerate(clause_permutation):
out._clauses[new]=tuple( substitution[l] for l in cnf._clauses[old])
# return the formula
assert out._check_coherence(force=True)
return out