723 lines
25 KiB
Python
723 lines
25 KiB
Python
# pyRCV2: Preferential vote counting
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# Copyright © 2020–2021 Lee Yingtong Li (RunasSudo)
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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__pragma__ = lambda x: None
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from pyRCV2.model import CandidateState, CountCard, CountCompleted, CountStepResult
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import pyRCV2.numbers
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from pyRCV2.numbers import Num
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from pyRCV2.safedict import SafeDict
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import pyRCV2.ties
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class STVException(Exception):
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def __init__(self, message):
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Exception.__init__(self)
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self.message = message
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class BaseSTVCounter:
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"""
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Basic STV counter for various different variations
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"""
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def __init__(self, election, options=None):
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self.election = election
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# Default options
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self.options = {
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'bulk_elect': True, # Bulk election?
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'bulk_exclude': False, # Bulk exclusion?
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'defer_surpluses': False, # Defer surpluses?
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'quota': 'droop', # 'droop', 'droop_exact', 'hare' or 'hare_exact'
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'quota_criterion': 'geq', # 'geq' or 'gt'
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'quota_mode': 'static', # 'static', 'progressive' or 'ers97'
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'surplus_order': 'size', # 'size' or 'order'
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'papers': 'both', # 'both' or 'transferable'
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'exclusion': 'one_round', # 'one_round', 'parcels_by_order', 'by_value' or 'wright'
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'ties': [], # List of tie strategies (e.g. TiesRandom)
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'round_quota': None, # Number of decimal places or None
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'round_votes': None, # Number of decimal places or None
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'round_tvs': None, # Number of decimal places or None
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'round_weights': None, # Number of decimal places or None
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}
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if options is not None:
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self.options.update(options)
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self.candidates = SafeDict([(c, CountCard()) for c in self.election.candidates])
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self.exhausted = CountCard()
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self.loss_fraction = CountCard()
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self.total_orig = sum((b.value for b in self.election.ballots), Num('0'))
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self.logs = []
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self.step_results = []
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self.num_elected = 0
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self.num_excluded = 0
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self.num_withdrawn = 0
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# Withdraw candidates
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for candidate in self.election.withdrawn:
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__pragma__('opov')
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self.candidates[candidate].state = CandidateState.WITHDRAWN
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__pragma__('noopov')
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self.num_withdrawn += 1
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def reset(self):
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"""
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Public function:
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Perform the first step (distribute first preferences)
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Does not reset the states of candidates, etc.
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"""
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self._exclusion = None # Optimisation to avoid re-collating/re-sorting ballots
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self.distribute_first_preferences()
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self.logs.append('First preferences distributed.')
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self.quota = None
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self.vote_required_election = None # For ERS97
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self.compute_quota()
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self.elect_meeting_quota()
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return self.make_result('First preferences')
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def distribute_first_preferences(self):
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"""
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Distribute first preferences (called as part of the reset() step)
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"""
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for ballot in self.election.ballots:
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__pragma__('opov')
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candidate = next((c for c in ballot.preferences if self.candidates[c].state == CandidateState.HOPEFUL), None)
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if candidate is not None:
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self.candidates[candidate].transfers += ballot.value
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if len(self.candidates[candidate].parcels) == 0:
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self.candidates[candidate].parcels.append([(ballot, Num(ballot.value))])
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else:
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self.candidates[candidate].parcels[0].append((ballot, Num(ballot.value)))
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else:
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self.exhausted.transfers += ballot.value
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#self.exhausted.parcels[0].append((ballot, Num(ballot.value)))
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__pragma__('noopov')
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def step(self):
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"""
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Public function:
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Perform one step of the STV count
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"""
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# Step count cards
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self.step_count_cards()
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# Check if done
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result = self.before_surpluses()
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if result:
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return result
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# Distribute surpluses
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result = self.distribute_surpluses()
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if result:
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return result
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# Check if done (2)
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result = self.before_exclusion()
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if result:
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return result
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# Insufficient winners and no surpluses to distribute
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# Exclude the lowest ranked hopeful(s)
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result = self.exclude_candidates()
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if result:
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return result
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raise STVException('Unable to complete step') # pragma: no cover
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def step_count_cards(self):
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"""
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Reset the count cards for the beginning of a new step
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"""
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for candidate, count_card in self.candidates.items():
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count_card.step()
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self.exhausted.step()
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self.loss_fraction.step()
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def before_surpluses(self):
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"""
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Check if the count can be completed before distributing surpluses
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"""
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# Have sufficient candidates been elected?
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if self.num_elected >= self.election.seats:
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__pragma__('opov')
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return CountCompleted(
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'Count complete',
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self.logs,
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self.candidates,
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self.exhausted,
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self.loss_fraction,
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self.total + self.exhausted.votes + self.loss_fraction.votes,
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self.quota,
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self.vote_required_election,
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)
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__pragma__('noopov')
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# Are there just enough candidates to fill all the seats?
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if self.options['bulk_elect']:
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# Include EXCLUDING to avoid interrupting an exclusion
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if len(self.election.candidates) - self.num_withdrawn - self.num_excluded + sum(1 for c, cc in self.candidates.items() if cc.state == CandidateState.EXCLUDING) <= self.election.seats:
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# Declare elected all remaining candidates
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candidates_elected = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.HOPEFUL]
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if len(candidates_elected) == 1:
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self.logs.append(candidates_elected[0][0].name + ' is elected to fill the remaining vacancy.')
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else:
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self.logs.append(self.pretty_join([c.name for c, cc in candidates_elected]) + ' are elected to fill the remaining vacancies.')
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for candidate, count_card in candidates_elected:
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count_card.state = CandidateState.PROVISIONALLY_ELECTED
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self.num_elected += 1
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count_card.order_elected = self.num_elected
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return self.make_result('Bulk election')
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def can_defer_surpluses(self, has_surplus):
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"""
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Determine if the specified surpluses can be deferred
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"""
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# Do not defer if this could change the last 2 candidates
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__pragma__('opov')
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total_surpluses = sum((cc.votes - self.quota for c, cc in has_surplus), Num(0))
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__pragma__('noopov')
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hopefuls = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.HOPEFUL]
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hopefuls.sort(key=lambda x: x[1].votes)
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__pragma__('opov')
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if total_surpluses > hopefuls[1][1].votes - hopefuls[0][1].votes:
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return False
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__pragma__('noopov')
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# Do not defer if this could affect a bulk exclusion
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if self.options['bulk_exclude']:
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to_bulk_exclude = self.candidates_to_bulk_exclude(hopefuls)
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if len(to_bulk_exclude) > 0:
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total_excluded = sum((cc.votes for c, cc in to_bulk_exclude), Num(0))
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__pragma__('opov')
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if total_surpluses > hopefuls[len(to_bulk_exclude) + 1][1].votes - total_excluded:
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return False
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__pragma__('opov')
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# Can defer surpluses
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self.logs.append('Distribution of surpluses totalling ' + total_surpluses.pp(2) + ' votes will be deferred.')
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return True
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def distribute_surpluses(self):
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"""
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Distribute surpluses, if any
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"""
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# Do not interrupt an exclusion
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if any(cc.state == CandidateState.EXCLUDING for c, cc in self.candidates.items()):
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return
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candidate_surplus, count_card = None, None
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# Are we distributing a surplus?
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has_surplus = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.DISTRIBUTING_SURPLUS]
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if len(has_surplus) > 0:
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candidate_surplus, count_card = has_surplus[0]
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else:
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# Do surpluses need to be distributed?
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__pragma__('opov')
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has_surplus = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.PROVISIONALLY_ELECTED and cc.votes > self.quota]
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__pragma__('noopov')
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if len(has_surplus) > 0:
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# Distribute surpluses in specified order
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if self.options['surplus_order'] == 'size':
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has_surplus.sort(key=lambda x: x[1].votes, reverse=True)
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elif self.options['surplus_order'] == 'order':
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has_surplus.sort(key=lambda x: x[1].order_elected)
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else: # pragma: no cover
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raise STVException('Invalid surplus order option')
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# Attempt to defer all remaining surpluses if possible
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if self.options['defer_surpluses']:
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if self.can_defer_surpluses(has_surplus):
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has_surplus = []
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if len(has_surplus) > 0:
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# Cannot defer any surpluses
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if self.options['surplus_order'] == 'size':
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candidate_surplus, count_card = self.choose_highest(has_surplus) # May need to break ties
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elif self.options['surplus_order'] == 'order':
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candidate_surplus, count_card = has_surplus[0] # Ties were already broken when these were assigned
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if candidate_surplus is not None:
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count_card.state = CandidateState.DISTRIBUTING_SURPLUS
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__pragma__('opov')
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surplus = count_card.votes - self.quota
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__pragma__('noopov')
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# Transfer surplus
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self.do_surplus(candidate_surplus, count_card, surplus)
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# Declare elected any candidates meeting the quota as a result of surpluses
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self.compute_quota()
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self.elect_meeting_quota()
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return self.make_result('Surplus of ' + candidate_surplus.name)
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def do_surplus(self, candidate_surplus, count_card, surplus):
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"""
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Transfer the surplus of the given candidate
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Subclasses must override this function
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"""
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raise NotImplementedError('Method not implemented') # pragma: no cover
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def before_exclusion(self):
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"""
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Check before excluding a candidate
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"""
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# If we did not perform bulk election in before_surpluses: Are there just enough candidates to fill all the seats?
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if not self.options['bulk_elect']:
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if len(self.election.candidates) - self.num_withdrawn - self.num_excluded <= self.election.seats:
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# Declare elected one remaining candidate at a time
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hopefuls = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.HOPEFUL]
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hopefuls.sort(key=lambda x: x[1].votes, reverse=True)
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candidate_elected, count_card = self.choose_highest(hopefuls)
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count_card.state = CandidateState.PROVISIONALLY_ELECTED
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self.num_elected += 1
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count_card.order_elected = self.num_elected
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return self.make_result('Bulk election')
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def exclude_candidates(self):
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"""
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Exclude the lowest ranked hopeful(s)
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"""
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candidates_excluded = self.candidates_to_exclude()
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for candidate, count_card in candidates_excluded:
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if count_card.state != CandidateState.EXCLUDING:
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count_card.state = CandidateState.EXCLUDING
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self.num_excluded += 1
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count_card.order_elected = -self.num_excluded
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# Handle Wright STV
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if self.options['exclusion'] == 'wright':
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for candidate, count_card in candidates_excluded:
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count_card.state = CandidateState.EXCLUDED
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# Reset the count
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# Carry over certain candidate states
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new_candidates = SafeDict()
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for candidate, count_card in self.candidates.items():
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new_count_card = CountCard()
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if count_card.state == CandidateState.WITHDRAWN:
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new_count_card.state = CandidateState.WITHDRAWN
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elif count_card.state == CandidateState.EXCLUDED:
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new_count_card.state = CandidateState.EXCLUDED
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__pragma__('opov')
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new_candidates[candidate] = new_count_card
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__pragma__('noopov')
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self.candidates = new_candidates
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self.exhausted = CountCard()
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self.loss_fraction = CountCard()
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self.num_elected = 0
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step_results = self.step_results # Carry over step results
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result = self.reset()
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self.step_results = step_results
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result.comment = 'Exclusion of ' + ', '.join([c.name for c, cc in candidates_excluded])
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return result
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# Exclude this candidate
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self.do_exclusion(candidates_excluded)
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# Declare any candidates meeting the quota as a result of exclusion
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self.compute_quota()
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self.elect_meeting_quota()
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return self.make_result('Exclusion of ' + ', '.join([c.name for c, cc in candidates_excluded]))
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def candidates_to_bulk_exclude(self, hopefuls):
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"""
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Determine which candidates can be bulk excluded
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Returns List[Tuple[Candidate, CountCard]]
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"""
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remaining_candidates = len(self.election.candidates) - self.num_withdrawn - self.num_excluded
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__pragma__('opov')
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total_surpluses = sum((cc.votes - self.quota for c, cc in self.candidates.items() if cc.votes > self.quota), Num(0))
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__pragma__('noopov')
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# Attempt to exclude as many candidates as possible
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for i in range(0, len(hopefuls)):
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try_exclude = hopefuls[0:len(hopefuls)-i]
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# Do not exclude if this splits tied candidates
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__pragma__('opov')
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if i != 0 and try_exclude[len(hopefuls)-i-1][1].votes == hopefuls[len(hopefuls)-i][1].votes:
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continue
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__pragma__('noopov')
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# Do not exclude if this leaves insufficient candidates
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if remaining_candidates - len(try_exclude) < self.election.seats:
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continue
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# Do not exclude if this could change the order of exclusion
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total_votes = sum((cc.votes for c, cc in try_exclude), Num(0))
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__pragma__('opov')
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if i != 0 and total_votes + total_surpluses > hopefuls[len(hopefuls)-i][1].votes:
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continue
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__pragma__('noopov')
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# Can bulk exclude
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return try_exclude
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return []
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def candidates_to_exclude(self):
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"""
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Determine the candidate(s) to exclude
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Returns List[Tuple[Candidate, CountCard]]
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"""
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# Continue current exclusion if applicable
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if self._exclusion is not None:
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self.logs.append('Continuing exclusion of ' + self.pretty_join([c.name for c, cc in self._exclusion[0]]) + '.')
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__pragma__('opov')
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return self._exclusion[0]
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__pragma__('noopov')
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hopefuls = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.HOPEFUL]
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hopefuls.sort(key=lambda x: x[1].votes)
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candidates_excluded = []
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# Bulk exclusion
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if self.options['bulk_exclude']:
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if self.options['exclusion'] == 'parcels_by_order':
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# Ordering of parcels is not defined in this case
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raise STVException('Cannot use bulk_exclude with parcels_by_order')
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candidates_excluded = self.candidates_to_bulk_exclude(hopefuls)
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if len(candidates_excluded) > 0:
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if len(candidates_excluded) == 1:
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self.logs.append('No surpluses to distribute, so ' + candidates_excluded[0][0].name + ' is excluded.')
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else:
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self.logs.append('No surpluses to distribute, so ' + self.pretty_join([c.name for c, cc in candidates_excluded]) + ' are excluded.')
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else:
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candidates_excluded = [self.choose_lowest(hopefuls)]
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self.logs.append('No surpluses to distribute, so ' + candidates_excluded[0][0].name + ' is excluded.')
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return candidates_excluded
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def do_exclusion(self, candidates_excluded):
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"""
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Exclude the given candidate and transfer the votes
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Subclasses must override this function
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"""
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raise NotImplementedError('Method not implemented') # pragma: no cover
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def compute_quota(self):
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"""
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Recount total votes and (if applicable) recalculate the quota
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"""
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__pragma__('opov')
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self.total = sum((cc.votes for c, cc in self.candidates.items()), Num('0'))
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self.loss_fraction.transfers += (self.total_orig - self.total - self.exhausted.votes) - self.loss_fraction.votes
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if self.quota is None or self.options['quota_mode'] == 'progressive':
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if self.options['quota'] == 'droop' or self.options['quota'] == 'droop_exact':
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self.quota = self.total / Num(self.election.seats + 1)
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elif self.options['quota'] == 'hare' or self.options['quota'] == 'hare_exact':
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self.quota = self.total / Num(self.election.seats)
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else:
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raise STVException('Invalid quota option') # pragma: no cover
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if self.options['round_quota'] is not None:
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if self.options['quota'] == 'droop' or self.options['quota'] == 'hare':
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# Increment to next available increment
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factor = Num(10).__pow__(self.options['round_quota'])
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__pragma__('opov')
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self.quota = ((self.quota * factor).__floor__() + Num(1)) / factor
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__pragma__('noopov')
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else:
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# Round up (preserving the original quota if exact)
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self.quota = self.quota.round(self.options['round_quota'], self.quota.ROUND_UP)
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self.logs.append(self.total.pp(2) + ' usable votes, so the quota is ' + self.quota.pp(2) + '.')
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__pragma__('noopov')
|
|
|
|
if self.options['quota_mode'] == 'ers97' and self.num_elected < self.election.seats:
|
|
# Calculate the total active vote
|
|
__pragma__('opov')
|
|
orig_vre = self.vote_required_election
|
|
total_active_vote = \
|
|
sum((cc.votes for c, cc in self.candidates.items() if cc.state == CandidateState.HOPEFUL or cc.state == CandidateState.EXCLUDING), Num('0')) + \
|
|
sum((cc.votes - self.quota for c, cc in self.candidates.items() if (cc.state == CandidateState.PROVISIONALLY_ELECTED or cc.state == CandidateState.DISTRIBUTING_SURPLUS or cc.state == CandidateState.ELECTED) and cc.votes > self.quota), Num('0'))
|
|
self.vote_required_election = total_active_vote / Num(self.election.seats - self.num_elected + 1)
|
|
if self.options['round_votes'] is not None:
|
|
self.vote_required_election = self.vote_required_election.round(self.options['round_votes'], self.vote_required_election.ROUND_UP)
|
|
if (orig_vre is None or self.vote_required_election != orig_vre) and self.vote_required_election < self.quota:
|
|
self.logs.append('Total active vote is ' + total_active_vote.pp(2) + ', so the vote required for election is ' + self.vote_required_election.pp(2) + '.')
|
|
__pragma__('noopov')
|
|
|
|
def meets_quota(self, count_card):
|
|
"""
|
|
Determine if the given candidate meets the quota
|
|
"""
|
|
|
|
if self.options['quota_criterion'] == 'geq':
|
|
__pragma__('opov')
|
|
return count_card.votes >= self.quota or (self.options['quota_mode'] == 'ers97' and count_card.votes >= self.vote_required_election)
|
|
__pragma__('noopov')
|
|
elif self.options['quota_criterion'] == 'gt':
|
|
__pragma__('opov')
|
|
return count_card.votes > self.quota or (self.options['quota_mode'] == 'ers97' and count_card.votes > self.vote_required_election)
|
|
__pragma__('noopov')
|
|
else:
|
|
raise STVException('Invalid quota criterion') # pragma: no cover
|
|
|
|
def elect_meeting_quota(self):
|
|
"""
|
|
Elect all candidates meeting the quota
|
|
"""
|
|
|
|
# Does a candidate meet the quota?
|
|
meets_quota = [(c, cc) for c, cc in self.candidates.items() if cc.state == CandidateState.HOPEFUL and self.meets_quota(cc)]
|
|
|
|
if len(meets_quota) > 0:
|
|
meets_quota.sort(key=lambda x: x[1].votes, reverse=True)
|
|
if len(meets_quota) == 1:
|
|
self.logs.append(meets_quota[0][0].name + ' meets the quota and is elected.')
|
|
else:
|
|
self.logs.append(self.pretty_join([c.name for c, cc in meets_quota]) + ' meet the quota and are elected.')
|
|
|
|
# Declare elected any candidate who meets the quota
|
|
while len(meets_quota) > 0:
|
|
x = self.choose_highest(meets_quota)
|
|
candidate, count_card = x[0], x[1]
|
|
|
|
count_card.state = CandidateState.PROVISIONALLY_ELECTED
|
|
self.num_elected += 1
|
|
count_card.order_elected = self.num_elected
|
|
|
|
meets_quota.remove(x)
|
|
|
|
if self.options['quota_mode'] == 'ers97':
|
|
self.compute_quota() # Vote required for election may have changed
|
|
|
|
if self.options['quota_mode'] == 'ers97':
|
|
self.elect_meeting_quota() # Repeat as the vote required for election may have changed
|
|
return
|
|
|
|
def describe_options(self):
|
|
result = []
|
|
if self.options['quota'] != 'droop':
|
|
result.append('--quota ' + self.options['quota'])
|
|
if self.options['quota_criterion'] != 'geq':
|
|
result.append('--quota-criterion ' + self.options['quota_criterion'])
|
|
if self.options['quota_mode'] != 'static':
|
|
result.append('--quota-mode ' + self.options['quota_mode'])
|
|
if not self.options['bulk_elect']:
|
|
result.append('--no-bulk-elect')
|
|
if self.options['bulk_exclude']:
|
|
result.append('--bulk-exclude')
|
|
if self.options['defer_surpluses']:
|
|
result.append('--defer-surpluses')
|
|
if pyRCV2.numbers._numclass is pyRCV2.numbers.Rational:
|
|
result.append('--numbers rational')
|
|
elif pyRCV2.numbers._numclass is pyRCV2.numbers.Native:
|
|
result.append('--numbers native')
|
|
elif pyRCV2.numbers._numclass is pyRCV2.numbers.FixedGuarded:
|
|
result.append('--numbers gfixed')
|
|
if pyRCV2.numbers.get_dps() != 5:
|
|
result.append('--decimals ' + str(pyRCV2.numbers.get_dps()))
|
|
else:
|
|
# Fixed
|
|
if pyRCV2.numbers.get_dps() != 5:
|
|
result.append('--decimals ' + str(pyRCV2.numbers.get_dps()))
|
|
if self.options['round_quota'] is not None:
|
|
result.append('--round-quota ' + str(self.options['round_quota']))
|
|
if self.options['round_votes'] is not None:
|
|
result.append('--round-votes ' + str(self.options['round_votes']))
|
|
if self.options['round_tvs'] is not None:
|
|
result.append('--round-tvs ' + str(self.options['round_tvs']))
|
|
if self.options['round_weights'] is not None:
|
|
result.append('--round-weights ' + str(self.options['round_weights']))
|
|
if self.options['surplus_order'] != 'size':
|
|
result.append('--surplus-order ' + self.options['surplus_order'])
|
|
if self.options['papers'] == 'transferable':
|
|
result.append('--transferable-only')
|
|
if self.options['exclusion'] != 'one_round':
|
|
result.append('--exclusion ' + self.options['exclusion'])
|
|
if len(self.options['ties']) == 1 and isinstance(self.options['ties'][0], pyRCV2.ties.TiesPrompt):
|
|
pass
|
|
else:
|
|
for t in self.options['ties']:
|
|
if isinstance(t, pyRCV2.ties.TiesBackwards):
|
|
result.append('--ties backwards')
|
|
elif isinstance(t, pyRCV2.ties.TiesForwards):
|
|
result.append('--ties forwards')
|
|
elif isinstance(t, pyRCV2.ties.TiesRandom):
|
|
result.append('--ties random')
|
|
result.append('--random-seed ' + t.random.seed)
|
|
elif isinstance(t, pyRCV2.ties.TiesPrompt):
|
|
result.append('--ties prompt')
|
|
return ' '.join(result)
|
|
|
|
# -----------------
|
|
# UTILITY FUNCTIONS
|
|
# -----------------
|
|
|
|
def next_preferences(self, parcels):
|
|
"""
|
|
Examine the specified ballots and group ballot papers by next available preference
|
|
"""
|
|
# SafeDict: Candidate -> [List[Ballot], ballots, votes]
|
|
next_preferences = SafeDict([(c, [[], Num('0'), Num('0')]) for c, cc in self.candidates.items()])
|
|
total_ballots = Num('0')
|
|
total_votes = Num('0')
|
|
|
|
next_exhausted = []
|
|
exhausted_ballots = Num('0')
|
|
exhausted_votes = Num('0')
|
|
|
|
for parcel in parcels:
|
|
for ballot, ballot_value in parcel:
|
|
__pragma__('opov')
|
|
total_ballots += ballot.value
|
|
total_votes += ballot_value
|
|
candidate = next((c for c in ballot.preferences if self.candidates[c].state == CandidateState.HOPEFUL), None)
|
|
|
|
if candidate is not None:
|
|
next_preferences[candidate][0].append((ballot, ballot_value))
|
|
next_preferences[candidate][1] += ballot.value
|
|
next_preferences[candidate][2] += ballot_value
|
|
else:
|
|
next_exhausted.append((ballot, ballot_value))
|
|
exhausted_ballots += ballot.value
|
|
exhausted_votes += ballot_value
|
|
|
|
__pragma__('noopov')
|
|
|
|
return next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes
|
|
|
|
def choose_lowest(self, l):
|
|
"""
|
|
Provided a list of tuples (Candidate, CountCard), sorted in ASCENDING order of votes, choose the tuple with the fewest votes, breaking ties appropriately
|
|
"""
|
|
|
|
if len(l) == 1:
|
|
return l[0]
|
|
|
|
__pragma__('opov')
|
|
# Do not use (c, cc) for c, cc in ... as this will break equality in JS
|
|
tied = [x for x in l if x[1].votes == l[0][1].votes]
|
|
__pragma__('noopov')
|
|
|
|
if len(tied) == 1:
|
|
return tied[0]
|
|
|
|
# A tie exists
|
|
for tie in self.options['ties']:
|
|
result = tie.choose_lowest(tied)
|
|
if result is not None:
|
|
self.logs.append('A tie for last place was resolved ' + tie.adverb + ' against ' + result[0].name + '.')
|
|
return result
|
|
|
|
raise STVException('Unable to resolve tie')
|
|
|
|
def choose_highest(self, l):
|
|
"""
|
|
Provided a list of tuples (Candidate, CountCard), sorted in DESCENDING order of votes, choose the tuple with the most votes, breaking ties appropriately
|
|
"""
|
|
|
|
if len(l) == 1:
|
|
return l[0]
|
|
|
|
__pragma__('opov')
|
|
# Do not use (c, cc) for c, cc in ... as this will break equality in JS
|
|
tied = [x for x in l if x[1].votes == l[0][1].votes]
|
|
__pragma__('noopov')
|
|
|
|
if len(tied) == 1:
|
|
return tied[0]
|
|
|
|
# A tie exists
|
|
for tie in self.options['ties']:
|
|
result = tie.choose_highest(tied)
|
|
if result is not None:
|
|
self.logs.append('A tie for first place was resolved ' + tie.adverb + ' in favour of ' + result[0].name + '.')
|
|
return result
|
|
|
|
raise STVException('Unable to resolve tie')
|
|
|
|
def round_votes(self, num):
|
|
if self.options['round_votes'] is None:
|
|
return num
|
|
return num.round(self.options['round_votes'], num.ROUND_DOWN)
|
|
|
|
def round_weight(self, num):
|
|
if self.options['round_weights'] is None:
|
|
return num
|
|
return num.round(self.options['round_weights'], num.ROUND_DOWN)
|
|
|
|
def round_tv(self, num):
|
|
if self.options['round_tvs'] is None:
|
|
return num
|
|
return num.round(self.options['round_tvs'], num.ROUND_DOWN)
|
|
|
|
def make_result(self, comment):
|
|
__pragma__('opov')
|
|
result = CountStepResult(
|
|
comment,
|
|
self.logs,
|
|
self.candidates,
|
|
self.exhausted,
|
|
self.loss_fraction,
|
|
self.total + self.exhausted.votes + self.loss_fraction.votes,
|
|
self.quota,
|
|
self.vote_required_election,
|
|
)
|
|
__pragma__('noopov')
|
|
self.logs = []
|
|
self.step_results.append(result)
|
|
return result
|
|
|
|
def pretty_join(self, strs):
|
|
if len(strs) == 0:
|
|
return ''
|
|
if len(strs) == 1:
|
|
return strs[0]
|
|
if len(strs) == 2:
|
|
return strs[0] + ' and ' + strs[1]
|
|
return ', '.join(strs[0:-1]) + ' and ' + strs[len(strs)-1]
|