Source code for whalrus.rules.rule_two_round

# -*- coding: utf-8 -*-
"""
Copyright Sylvain Bouveret, Yann Chevaleyre and Fran├žois 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
from whalrus.rules.rule import Rule
from whalrus.rules.rule_borda import RuleBorda
from whalrus.rules.rule_plurality import RulePlurality
from whalrus.rules.rule_sequential_elimination import RuleSequentialElimination
from whalrus.eliminations.elimination import Elimination
from whalrus.eliminations.elimination_last import EliminationLast


[docs]class RuleTwoRound(RuleSequentialElimination): # noinspection PyUnresolvedReferences """ The two-round system. Parameters ---------- args Cf. parent class. rule1 The first rule. Default: :class:`RulePlurality`. rule2 The second rule. Default: :class:`RulePlurality`. elimination : Elimination The elimination algorithm used during the first round. Default: :class:`EliminationLast` with ``k=-2``, which only keeps the 2 best candidates. kwargs Cf. parent class. Examples -------- With its default settings, this class implements the classic two-round system, using plurality at both rounds: >>> rule = RuleTwoRound(['a > b > c > d > e', 'b > a > c > d > e', 'c > a > b > d > e'], ... weights=[2, 2, 1]) >>> rule.first_round_.rule_.gross_scores_ {'a': 2, 'b': 2, 'c': 1, 'd': 0, 'e': 0} >>> rule.second_round_.gross_scores_ {'a': 3, 'b': 2} Using the options, some more exotic two-round systems can be defined, such as changing the rule of a round: >>> rule = RuleTwoRound(['a > b > c > d > e', 'b > a > c > d > e', 'c > a > b > d > e'], ... weights=[2, 2, 1], rule1=RuleBorda()) >>> rule.first_round_.rule_.gross_scores_ {'a': 17, 'b': 16, 'c': 12, 'd': 5, 'e': 0} >>> rule.second_round_.gross_scores_ {'a': 3, 'b': 2} ... or changing the elimination algorithm: >>> rule = RuleTwoRound(['a > b > c > d > e', 'b > a > c > d > e', 'c > a > b > d > e'], ... weights=[2, 2, 1], elimination=EliminationLast(k=-3)) >>> rule.first_round_.rule_.gross_scores_ {'a': 2, 'b': 2, 'c': 1, 'd': 0, 'e': 0} >>> rule.second_round_.gross_scores_ {'a': 2, 'b': 2, 'c': 1} """ def __init__(self, *args, rule1: Rule = None, rule2: Rule = None, elimination: Elimination = None, **kwargs): if rule1 is None: rule1 = RulePlurality() if rule2 is None: rule2 = RulePlurality() if elimination is None: elimination = EliminationLast(k=-2) super().__init__(*args, rules=[rule1, rule2], eliminations=[elimination], **kwargs) @cached_property def first_round_(self) -> Elimination: """Elimination: The first round. This is just a shortcut for ``self.elimination_rounds_[0]``. """ return self.elimination_rounds_[0] @cached_property def second_round_(self) -> Rule: """Rule: The second round. This is just an alternative name for ``self.final_round_``. """ return self.final_round_