Example #1
0
  if unsat(a) or sat(f): return f,a
  minj = f.index(min(f,key=len))  # clause with fewest literals
  if len(f[minj])==0:
    a[0] = UNSAT
    return f,a
  if len(f[minj])==1: 
    fixliteral(f[minj][0], f, a)
    return backsat(f,a)
  #split: 2 possible bool. vals for literal f[minj][0]
  #print "split A:", f[minj][0]
  fcopy, acopy = mycopy(f,a)
  fixliteral(f[minj][0], f, a)  # f[minj][0] True
  f,a = backsat(f,a)
  if sat(f): return f, a
  f,a = fcopy, acopy
  #print "split B:", -f[minj][0]
  fixliteral(-f[minj][0], f, a) # f[minj][0] False
  return backsat(f, a)

#myf=[[-5,-6],[-3,5],[-2,5],[1,-6],[1,-4],[1,-3],[2,3],[2,6],[3,-5],[3,4],[4,-5],[5,-6]]
#myf=[[-4,-5,6],[-4,5,-6],[-2,4,-5],[-2,5,-6],[-1,-3,-4],[-1,-3,4],[-1,4,-6],[1,-4,5],[1,-3,-5],[1,-3,4],[1,5,-6],[2,5,6],[3,-5,-6],[4,-5,6],[4,5,-6],[4,5,6]]

n,m = 20,90  #max m is n choose k times 2^k, where k=2or3
myf = formula(n,3,m)
print "\nrandom formula",n,"vars",m,"clauses"
showf(myf)
print ''
asn = [UNKNOWN]*n
f,a = backsat(myf,asn)
showfa(f,a)
Example #2
0
            else:
                print('formula unsatisfiable')
                return f, a  #
        else:  # f is not the empty list, a is not the empty string
            ndx = ind_short(f)
            lenj = len(f[ndx])
            if lenj == 1:  # fix literal
                f, a = fix_literal(f[ndx][0], f, a)
            elif lenj >= 2:  #try both possible values
                fcopy, acopy = deepcopy(f), a
                f, a = fix_literal(f[ndx][0], f, a)  # try now
                newf, newa = fix_literal(-fcopy[ndx][0], fcopy, acopy)
                candidates.append((newf, newa))  # try later


def backsolve(n, myf):
    asn = UNKNOWN * n
    backsat(myf, asn)


n, k, m = 22, 3, 100
f = formula(n, k, m)
#f = [[1, 2, 3], [1, 2, -3], [1, 2, -4], [1, -2, 3], [1, -2, -4], [1, 3, 4], [1, 3, -4], [-1, 2, -3], [-1, 2, -4], [-1, -2, -3], [-1, -2, 4], [-1, -2, -4], [-1, 3, 4], [2, -3, -4], [-2, 3, 4], [-2, -3, -4]]
f2 = deepcopy(f)
print('formula with', n, 'vars', m, 'clauses')
print('')
backsolve(n, f)

print('\nverify with bfsolve')
bfsolve(n, f2, True)
Example #3
0
  fcopy, acopy = mycopy(f,a)
  fixliteral(f[minj][0], f, a)  # f[minj][0] True
  f,a = backsat(f,a)
  if sat(f): return f, a
  f,a = fcopy, acopy
  #print "split B:", -f[minj][0]
  fixliteral(-f[minj][0], f, a) # f[minj][0] False
  return backsat(f, a)

def backsolve(n,myf):
  asn = [UNKNOWN]*n
  f,a = backsat(myf,asn)
  showfa(f,a)

#n,myf=6,[[-5,-6],[-3,5],[-2,5],[1,-6],[1,-4],[1,-3],[2,3],[2,6],[3,-5],[3,4],[4,-5],[5,-6]]
#n,myf=6,[[-4,-5,6],[-4,5,-6],[-2,4,-5],[-2,5,-6],[-1,-3,-4],[-1,-3,4],[-1,4,-6],[1,-4,5],[1,-3,-5],[1,-3,4],[1,5,-6],[2,5,6],[3,-5,-6],[4,-5,6],[4,5,-6],[4,5,6]]

#max m: (n choose k)(2^k)
#n, k, m = 20, 5, 400  # good example
n, k, m = 30, 5, 600 # backtrack yes, bf too slow

myf = formula(n,k,m)
n,myf = 5, [[1,-5],[-2,-3],[3,4],[-4,-5],[2,5],[-1,-5]]
n,myf = 5, [[1,-2],[1,3],[-2,-3],[2,4],[-3,-4],[3,-5],[3,5]]
myf2 = deepcopy(myf)
#print "\nrandom formula",n,"vars",m,"clauses"
#showf(myf)
#print ''
backsolve(n,myf)
bfsolve(n,myf2,TRUE)