Optimise next_preferences algorithm to avoid re-examining earlier preferences
Senate count from 9.02 to 8.22s
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@ -16,7 +16,7 @@
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__pragma__ = lambda x: None
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from pyRCV2.model import CandidateState, CountCard, CountCompleted, CountStepResult
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from pyRCV2.model import BallotInCount, 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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@ -101,15 +101,18 @@ class BaseSTVCounter:
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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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for i, candidate in enumerate(ballot.preferences):
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count_card = self.candidates[candidate]
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if count_card.state == CandidateState.HOPEFUL:
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count_card.transfers += ballot.value
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if len(count_card.parcels) == 0:
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count_card.parcels.append([BallotInCount(ballot, Num(ballot.value), i)])
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else:
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count_card.parcels[0].append(BallotInCount(ballot, Num(ballot.value), i))
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break
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else:
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# No available preference
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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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@ -601,7 +604,7 @@ class BaseSTVCounter:
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"""
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Examine the specified ballots and group ballot papers by next available preference
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"""
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# SafeDict: Candidate -> [List[Ballot], ballots, votes]
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# SafeDict: Candidate -> [List[BallotInCount], ballots, votes]
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next_preferences = SafeDict([(c, [[], Num('0'), Num('0')]) for c, cc in self.candidates.items()])
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total_ballots = Num('0')
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total_votes = Num('0')
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@ -611,21 +614,25 @@ class BaseSTVCounter:
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exhausted_votes = Num('0')
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for parcel in parcels:
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for ballot, ballot_value in parcel:
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for bc in parcel:
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__pragma__('opov')
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total_ballots += ballot.value
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total_votes += ballot_value
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candidate = next((c for c in ballot.preferences if self.candidates[c].state == CandidateState.HOPEFUL), None)
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total_ballots += bc.ballot.value
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total_votes += bc.ballot_value
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if candidate is not None:
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next_preferences[candidate][0].append((ballot, ballot_value))
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next_preferences[candidate][1] += ballot.value
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next_preferences[candidate][2] += ballot_value
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for i in range(bc.last_preference + 1, len(bc.ballot.preferences)):
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candidate = bc.ballot.preferences[i]
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count_card = self.candidates[candidate]
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if count_card.state == CandidateState.HOPEFUL:
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next_preferences[candidate][0].append(BallotInCount(bc.ballot, bc.ballot_value, i))
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next_preferences[candidate][1] += bc.ballot.value
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next_preferences[candidate][2] += bc.ballot_value
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break
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else:
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next_exhausted.append((ballot, ballot_value))
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exhausted_ballots += ballot.value
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exhausted_votes += ballot_value
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# No next available preference
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next_exhausted.append(bc)
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exhausted_ballots += bc.ballot.value
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exhausted_votes += bc.ballot_value
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__pragma__('noopov')
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return next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes
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@ -119,37 +119,38 @@ class BaseGregorySTVCounter(BaseSTVCounter):
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self.candidates[candidate].transfers += self.round_votes(num_units * tv)
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__pragma__('noopov')
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for ballot, ballot_value in cand_ballots:
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for bc in cand_ballots:
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__pragma__('opov')
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if self.options['papers'] == 'transferable':
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if transferable_votes > surplus:
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if self.options['round_tvs'] is None:
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if is_weighted:
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new_value = (ballot_value * surplus) / transferable_units
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new_value = (bc.ballot_value * surplus) / transferable_units
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else:
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new_value = (ballot.value * surplus) / transferable_units
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new_value = (bc.ballot.value * surplus) / transferable_units
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else:
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tv = self.round_tv(surplus / transferable_units)
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if is_weighted:
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new_value = ballot_value * tv
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new_value = bc.ballot_value * tv
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else:
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new_value = ballot.value * tv
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new_value = bc.ballot.value * tv
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else:
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new_value = ballot_value
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new_value = bc.ballot_value
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else:
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if self.options['round_tvs'] is None:
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if is_weighted:
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new_value = (ballot_value * surplus) / total_units
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new_value = (bc.ballot_value * surplus) / total_units
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else:
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new_value = (ballot.value * surplus) / total_units
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new_value = (bc.ballot.value * surplus) / total_units
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else:
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tv = self.round_tv(surplus / total_units)
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if is_weighted:
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new_value = ballot_value * tv
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new_value = bc.ballot_value * tv
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else:
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new_value = ballot.value * tv
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new_value = bc.ballot.value * tv
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new_parcel.append((ballot, self.round_weight(new_value)))
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bc.ballot_value = self.round_weight(new_value)
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new_parcel.append(bc)
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__pragma__('noopov')
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__pragma__('opov')
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@ -174,29 +175,29 @@ class BaseGregorySTVCounter(BaseSTVCounter):
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def do_exclusion(self, candidates_excluded):
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"""Implements BaseSTVCounter.do_exclusion"""
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# Optimisation: Pre-sort exclusion ballots if applicable
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# self._exclusion[1] -> list of ballots-per-stage, ballots-per-stage = List[Tuple[Candidate,List[Ballot+Value]]]
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# self._exclusion[1] -> list of ballots-per-stage ; ballots-per-stage = List[Tuple[Candidate,List[BallotInCount]]]
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if self._exclusion is None:
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if self.options['exclusion'] == 'one_round':
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self._exclusion = (candidates_excluded, [[(c, [b for p in cc.parcels for b in p]) for c, cc in candidates_excluded]])
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self._exclusion = (candidates_excluded, [[(c, [bc for p in cc.parcels for bc in p]) for c, cc in candidates_excluded]])
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elif self.options['exclusion'] == 'parcels_by_order':
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c, cc = candidates_excluded[0]
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self._exclusion = (candidates_excluded, [[(c, p)] for p in cc.parcels])
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elif self.options['exclusion'] == 'by_value':
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ballots = [(c, b, bv) for c, cc in candidates_excluded for p in cc.parcels for b, bv in p]
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ballots = [(c, bc) for c, cc in candidates_excluded for p in cc.parcels for bc in p]
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# Sort ballots by value
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__pragma__('opov')
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ballots.sort(key=lambda x: x[2] / x[1].value, reverse=True)
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# Round to 8 decimal places to consider equality
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# FIXME: Work out a better way of doing this
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ballots.sort(key=lambda x: x[1].ballot_value / x[1].ballot.value, reverse=True)
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if self.options['round_tvs']:
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ballots_by_value = groupby(ballots, lambda x: self.round_tv(x[2] / x[1].value))
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ballots_by_value = groupby(ballots, lambda x: self.round_tv(x[1].ballot_value / x[1].ballot.value))
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else:
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ballots_by_value = groupby(ballots, lambda x: (x[2] / x[1].value).round(8, x[2].ROUND_DOWN))
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# Round to 8 decimal places to consider equality
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# FIXME: Work out a better way of doing this
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ballots_by_value = groupby(ballots, lambda x: (x[1].ballot_value / x[1].ballot.value).round(8, x[1].ballot_value.ROUND_DOWN))
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__pragma__('noopov')
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# TODO: Can we combine ballots for each candidate within each stage?
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self._exclusion = (candidates_excluded, [[(c, [(b, bv)]) for c, b, bv in x] for x in ballots_by_value])
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self._exclusion = (candidates_excluded, [[(c, [bc]) for c, bc in x] for x in ballots_by_value])
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else:
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raise STVException('Invalid exclusion mode') # pragma: no cover
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@ -205,11 +206,11 @@ class BaseGregorySTVCounter(BaseSTVCounter):
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# Transfer votes
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next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes = self.next_preferences([bb for c, bb in this_exclusion])
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next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes = self.next_preferences([bc for c, bc in this_exclusion])
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if self.options['exclusion'] != 'one_round':
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__pragma__('opov')
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self.logs.append('Transferring ' + total_ballots.pp(0) + ' ballot papers, totalling ' + total_votes.pp(2) + ' votes, received at value ' + (this_exclusion[0][1][0][1] / this_exclusion[0][1][0][0].value).pp(2) + '.')
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self.logs.append('Transferring ' + total_ballots.pp(0) + ' ballot papers, totalling ' + total_votes.pp(2) + ' votes, received at value ' + (this_exclusion[0][1][0].ballot_value / this_exclusion[0][1][0].ballot.value).pp(2) + '.')
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__pragma__('noopov')
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for candidate, x in next_preferences.items():
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@ -225,9 +226,9 @@ class BaseGregorySTVCounter(BaseSTVCounter):
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self.candidates[candidate].transfers += self.round_votes(num_votes)
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__pragma__('noopov')
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for ballot, ballot_value in cand_ballots:
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for bc in cand_ballots:
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__pragma__('opov')
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new_parcel.append((ballot, ballot_value))
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new_parcel.append(bc)
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__pragma__('noopov')
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# Subtract votes
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@ -238,9 +239,9 @@ class BaseGregorySTVCounter(BaseSTVCounter):
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for candidate, ballots in this_exclusion:
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total_votes = Num(0)
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for ballot, ballot_value in ballots:
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for bc in ballots:
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__pragma__('opov')
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total_votes += ballot_value
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total_votes += bc.ballot_value
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__pragma__('noopov')
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__pragma__('opov')
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@ -33,7 +33,7 @@ class MeekCountCard(CountCard):
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result = MeekCountCard()
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result.orig_votes = self.orig_votes
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result.transfers = self.transfers
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result.parcels = [[(b[0].clone(), b[1]) for b in p] for p in self.parcels]
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#result.parcels = [[(b[0].clone(), b[1]) for b in p] for p in self.parcels]
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result.state = self.state
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result.order_elected = self.order_elected
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result.keep_value = keep_value
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@ -38,6 +38,10 @@ class CandidateState:
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WITHDRAWN = 60
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class Ballot:
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"""
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Represents a voter's (or if weighted, multiple voters') preferences
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"""
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def __init__(self, value, preferences):
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self.value = value
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self.preferences = preferences
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@ -45,6 +49,20 @@ class Ballot:
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def clone(self):
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return Ballot(self.value, self.preferences)
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class BallotInCount:
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"""
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Represents a Ballot held by a candidate at a particular value during the count
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"""
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__slots__ = ['ballot', 'ballot_value', 'last_preference']
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def __init__(self, ballot, ballot_value, last_preference):
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self.ballot = ballot
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self.ballot_value = ballot_value
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# Optimisation: Record the most-recently used preference so earlier preferences do not need to be later examined
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self.last_preference = last_preference
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class Election:
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"""
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Represents a BLT election
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