# -*- coding: utf-8 -*-
"""
Copyright Sylvain Bouveret, Yann Chevaleyre and François Durand
sylvain.bouveret@imag.fr, yann.chevaleyre@dauphine.fr, fradurand@gmail.com
This file is part of Whalrus.
Whalrus 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, either version 3 of the License, or
(at your option) any later version.
Whalrus 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 Whalrus. If not, see <http://www.gnu.org/licenses/>.
"""
from whalrus.utils.utils import cached_property, NiceSet
from whalrus.rules.rule import Rule
from whalrus.rules.rule_plurality import RulePlurality
from whalrus.rules.rule_borda import RuleBorda
from whalrus.priorities.priority import Priority
[docs]class RuleSequentialTieBreak(Rule):
"""
A rule by sequential tie-break.
Parameters
----------
args
Cf. parent class.
rules : list of Rule
kwargs
Cf. parent class.
Examples
--------
The winner is determined by the first rule. If there is a tie, it is broken by the second rule. Etc. There may
still be a tie at the end: in that case, it is broken by the tie-breaking rule of this object.
>>> rule = RuleSequentialTieBreak(
... ['a > d > e > b > c', 'b > d > e > a > c', 'c > d > e > a > b',
... 'd > e > b > a > c', 'e > d > b > a > c'],
... weights=[2, 2, 2, 1, 1],
... rules=[RulePlurality(), RuleBorda()], tie_break=Priority.ASCENDING)
>>> rule.rules_[0].gross_scores_
{'a': 2, 'b': 2, 'c': 2, 'd': 1, 'e': 1}
>>> rule.rules_[1].gross_scores_
{'a': 14, 'b': 14, 'c': 8, 'd': 25, 'e': 19}
>>> rule.order_
[{'a', 'b'}, {'c'}, {'d'}, {'e'}]
>>> rule.winner_
'a'
"""
def __init__(self, *args, rules: list = None, **kwargs):
self.rules = rules
super().__init__(*args, **kwargs)
@cached_property
def rules_(self) -> list:
"""list: The rules (once applied to the profile).
"""
return [rule(self.profile_converted_) for rule in self.rules]
@cached_property
def order_(self) -> list:
orders = [rule.order_ for rule in self.rules_]
# rank_tuples[a] will be (rank in order 0, rank in order 1, ...)
rank_tuples = {c: [] for c in self.candidates_}
for order in orders:
for i, tie_class in enumerate(order):
for c in tie_class:
rank_tuples[c].append(i)
rank_tuples = {k: tuple(v) for k, v in rank_tuples.items()}
# Now, sort by lexicographic order of "rank tuples"
return [NiceSet(k for k in rank_tuples.keys() if rank_tuples[k] == v)
for v in sorted(set(rank_tuples.values()))]
# TODO: some methods such as cowinners_ might be overridden for a better performance.