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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (C) 2009-2020 Authors of CryptoMiniSat, see AUTHORS file
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; version 2
# of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
from __future__ import print_function
import re
class XorToCNF:
def __init__(self):
self.cutsize = 4
def get_max_var(self, clause):
maxvar = 0
tmp = clause.strip()
if len(tmp) == 0:
return 0
assert re.search(r'^x? *-?\d+', tmp)
if tmp[0] == 'x':
tmp = tmp[1:]
for lit in tmp.split():
var = abs(int(lit))
maxvar = max(var, maxvar)
return maxvar
def convert(self, infilename, outfilename, num_extra_cls=0):
assert isinstance(self.cutsize, int)
if self.cutsize <= 2:
print("ERROR: The cut size MUST be larger or equal to 3")
exit(-1)
maxvar, numcls, extravars_needed, extracls_needed = self.get_stats(infilename)
fout = open(outfilename, "w")
fout.write("p cnf %d %d\n" %
(maxvar + extravars_needed,
numcls + extracls_needed + num_extra_cls))
fin = open(infilename, "r")
atvar = maxvar
for line in fin:
line = line.strip()
# skip empty line
if len(line) == 0:
continue
# skip header and comments
if line[0] == 'c' or line[0] == 'p':
continue
if line[0] == 'x':
# convert XOR to normal(s)
xorclauses, atvar = self.cut_up_xor_to_n(line, atvar)
for xorcl in xorclauses:
cls = self.xor_to_cnf_simple(xorcl)
for cl in cls:
fout.write(cl + "\n")
else:
# simply print normal clause
fout.write(line + "\n")
assert atvar == maxvar + extravars_needed
fout.close()
fin.close()
def popcount(self, x):
return bin(x).count('1')
def parse_xor(self, xorclause):
assert re.search(r'^x( *-?\d+ )*0$', xorclause)
tmp = xorclause[1:]
lits = [int(elem) for elem in tmp.split()]
assert lits[len(lits)-1] == 0
# remove last element, the 0
lits = lits[:len(lits)-1]
return lits
def xor_to_cnf_simple(self, xorclause, equals=True):
assert equals is True or equals is False
if equals is True:
equals = 1
else:
equals = 0
lits = self.parse_xor(xorclause)
# empty XOR clause is TRUE, so is NOT an empty clause (i.e. UNSAT)
if len(lits) == 0:
return []
ret = []
for i in range(2**(len(lits))):
# only the ones we need
cls = ""
if self.popcount(i) % 2 == equals:
continue
for at in range(len(lits)):
if ((i >> at) & 1) == 0:
cls += "%d " % lits[at]
else:
cls += "%d " % (-1*lits[at])
cls += "0"
ret.append(cls)
return ret
def cut_up_xor_to_n(self, xorclause, oldmaxvar):
assert self.cutsize > 2
lits = self.parse_xor(xorclause)
xors = []
# xor clause that doesn't need to be cut up
if len(lits) <= self.cutsize:
retcl = "x"
for lit in lits:
retcl += "%d " % lit
retcl += "0"
return [[retcl], oldmaxvar]
at = 0
newmaxvar = oldmaxvar
while(at < len(lits)):
# until when should we cut?
until = min(at + self.cutsize-1, len(lits))
# if in the middle, don't add so much
if at > 0 and until < len(lits):
until -= 1
thisxor = "x"
for i2 in range(at, until):
thisxor += "%d " % lits[i2]
# add the extra variables
if at == 0:
# beginning, add only one
thisxor += "%d 0" % (newmaxvar+1)
newmaxvar += 1
elif until == len(lits):
# end, only add the one we already made
thisxor += "-%d 0" % (newmaxvar)
else:
thisxor += "-%d %d 0" % (newmaxvar, newmaxvar+1)
newmaxvar += 1
xors.append(thisxor)
# move along where we are at
at = until
return [xors, newmaxvar]
def num_extra_vars_cls_needed(self, numlits):
def cls_for_plain_xor(numlits):
return 2**(numlits-1)
varsneeded = 0
clsneeded = 0
at = 0
while(at < numlits):
# at the beginning
if at == 0:
if numlits > self.cutsize:
at += self.cutsize-1
varsneeded += 1
clsneeded += cls_for_plain_xor(self.cutsize)
else:
at = numlits
clsneeded += cls_for_plain_xor(numlits)
# in the middle
elif at + (self.cutsize-1) < numlits:
at += self.cutsize-2
varsneeded += 1
clsneeded += cls_for_plain_xor(self.cutsize)
# at the end
else:
clsneeded += cls_for_plain_xor(numlits-at+1)
at = numlits
return [varsneeded, clsneeded]
def get_stats(self, infilename):
infile = open(infilename, "r")
maxvar = 0
numcls = 0
extravars_needed = 0
extracls_needed = 0
for line in infile:
line = line.strip()
# empty line, skip
if len(line) == 0:
continue
# header or comment
if line[0] == 'p' or line[0] == 'c':
continue
# get max var
maxvar = max(self.get_max_var(line), maxvar)
if line[0] == 'x':
e_var, e_clause = self.num_extra_vars_cls_needed(len(self.parse_xor(line)))
extravars_needed += e_var
extracls_needed += e_clause
else:
numcls += 1
infile.close()
return [maxvar, numcls, extravars_needed, extracls_needed]
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