2. Class PBConstraint

2.1. Constructor

PBConstraint(weightedlits: [WeightedLits], comparator, bound: int)

Creates an object to represents a Pseudo-Boolean constraint.

>>> import pypblib.pblib
>>> wl_list = [pypblib.pblib.WeightedLit(1,3),
              pypblib.pblib.WeightedLit(2,1),
              pypblib.pblib.WeightedLit(3,5)]
>>> constr = pypblib.pblib.PBConstraint(wl_list, pypblib.pblib.GEQ, 1)
>>> constr
+3x1+x2+5x3>=1

>>> from pypblib import pblib
>>> w1 = pblib.WeightedLit(1, 2)
>>> w2 = pblib.WeightedLit(2, 1)
>>> w3 = pblib.WeightedLit(3, -2)
>>> constr = pblib.PBConstraint([w1, w2, w3], pblib.LEQ, 1)
>>> constr
+2x1+x2-2x3<=1

PBConstraint(weightedlits: [WeightedLits], comparator, bound_geq: int, bound_leq: int)

Creates an object to represents a Pseudo-Boolean constraint, in case pblib.BOTH comparator and bound less-equal and greater-equal are different.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 2)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> comp = pblib.BOTH
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], comp, 2, 0)
>>> constr
0<=+2x1+x2-1x3<=2

2.3. Methods details

add_conditional(cond: int)

Adds a conditional to the constraint.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], comp, 2, 0)
>>> constr.add_conditional(3)
add_conditionals(conds: [int])

Adds a list of conditionals to the constraint.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], comp, 2, 0)
>>> constr.add_conditionals([1, 2])
get_conditionals() → [int]

Returns a list of conditionals.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> constr.add_conditionals([1, 2])
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], comp, 2, 0)
>>> cond = constr.get_conditionals()
>>> cond
[1, 2]
clear_conditional()

Removes all conditionals in a constraint.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], comp, 2, 0)
>>> constr.add_conditionals([1, 2])
>>> cond = constr.get_conditionals()
>>> cond
[1, 2]
>>> cond = constr.clear_conditionals()
>>> cond
>>>
get_comparator() → comparator

Returns an int to represents the comparator (GEQ = 0, LEQ = 1 and BOTH = 2).

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> constr = pblib.PBConstraint([wl1, wl2], pblib.GEQ, 1)
>>> comp = constr.get_comparator()
>>> print(comp)
0
get_leq() → long

Returns the less-equal value bound of the constraint.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> constr = pblib.PBConstraint([wl1, wl2], pblib.LEQ, 1)
>>> n = constr.get_leq()
>>> print(n)
1
get_geq() → long

Returns the greater-equal value bound of the constraint.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> constr = pblib.PBConstraint([wl1, wl2], pblib.GEQ, 0)
>>> n = constr.get_geq()
>>> print(n)
0
get_min_sum() → long

Returns the minimum sum of literals’ weights.

>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> wls = [wl1, wl2, wl3]
>>> constr = pblib.PBConstraint(wls, pblib.LEQ, 4)
>>> s = constr.get_min_sum()
>>> print("Min = ", s)
>>> Min = -1
get_max_sum() → long

Returns the maximum sum of literals’ weights.

>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> wls = [wl1, wl2, wl3]
>>> constr = pblib.PBConstraint(wls, pblib.LEQ, 4)
>>> s = constr.get_min_sum()
>>> print("Max = ", s)
>>> Max = 2
get_n() → int

Returns the number of weigted literals in the constraint.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> constr = pblib.PBConstraint([wl1, wl2], pblib.GEQ, 1)
>>> n = constr.get_n()
>>> print(n)
2
>>> wl3 = pblib.WeightedLit(3, 2)
>>> constr2 = pblib.PBConstraint([wl1, wl2, wl3], pblib.GEQ, 1)
>>> n2 = constr2.get_n()
>>> print(n2)
3
get_weighted_literals() → [WeightedLiterals]

Returns a copy of the vector of weighted literals which PBContraint contains.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 2)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, 2)
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], pblib.LEQ, 2)
>>> w_lits = constr.get_weighted_literals()
>>> print(w_lits)
[WeightedLit(lit=1, weight=2), WeightedLit(lit=2, weight=2), WeightedLit(lit=3, weight=2)]
>>> constr_2 = pblib.PBConstraint(w_lits, pblib.GEQ, 4)
>>> constr_2
+2x1+2x2+2x3>=4
get_geq_constraint() → PBConstraint

Takes a pseudo boolean constraint and returns a new PBConstraint changing the comparator to a greater-equal. However, the bound does not change. If the greater-equal bound is equal to zero (because the previous restriction had not been assigned any value), the bound will remain zero.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 2)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, 2)
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], pblib.LEQ, 2)
>>> constr
+2x1+2x2+2x3<=2
>>> constr_2 = constr.get_geq_constraint()
>>> constr_2
+2x1+2x2+2x3>=0
get_leq_constraint() → PBConstraint

Takes a pseudo boolean constraint and returns a new PBConstraint changing the comparator to a less-equal. However, the bound does not change. If the less-equal bound is equal to zero (because the previous restriction had not been assigned any value), the bound will remain zero.

>>> from pypblib import pblib
>>> wl1 = pblib.WeightedLit(1, 2)
>>> wl2 = pblib.WeightedLit(2, 2)
>>> wl3 = pblib.WeightedLit(3, 2)
>>> constr = pblib.PBConstraint([wl1, wl2, wl3], pblib.GEQ, 4)
>>> constr
+2x1+2x2+2x3>=4
>>> constr_2 = constr.get_leq_constraint()
>>> constr_2
+2x1+2x2+2x3<=0
set_comparator(comparator)

Sets the constraint’s comparator to specified value.

>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> wls = [wl1, wl2, wl3]
>>> constr = pblib.PBConstraint(wls, pblib.LEQ, 4)
>>> print(constr.get_comparator())
1
>>> constr.set_comparator(pblib.GEQ)
>>> print(constr.get_comparator())
0
set_leq(leq_bound: long)

Sets the less-equal bound to specified value.

>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> wls = [wl1, wl2, wl3]
>>> constr = pblib.PBConstraint(wls, pblib.LEQ, 2)
>>> print(constr.get_leq())
2
>>> constr.set_leq(1)
>>> print(constr.get_leq())
1
set_geq(geq_bound: long)

Sets the greater-equal bound to specified value.

>>> wl1 = pblib.WeightedLit(1, 1)
>>> wl2 = pblib.WeightedLit(2, 1)
>>> wl3 = pblib.WeightedLit(3, -1)
>>> wls = [wl1, wl2, wl3]
>>> constr = pblib.PBConstraint(wls, pblib.GEQ, 1)
>>> print(constr.get_geq())
1
>> constr.set_geq(0)
>> print(constr.get_geq())
0