Make Wright method a variant of regular STV as an exclusion method
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@ -66,10 +66,9 @@ Some STV counting rules provide, for example, that ‘no surplus shall be transf
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## Method (-m/--method)
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This dropdown allows you to select how ballots are transferred during surplus transfers or exclusions. The 2 recommended methods are:
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This dropdown allows you to select how ballots are transferred during surplus transfers or exclusions. The recommended method is:
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* Weighted inclusive Gregory: During surplus transfers, all applicable ballot papers of the transferring candidate are examined. Transfers are weighted according to the weights of the ballot papers.
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* Wright STV: Same as weighted inclusive Gregory, but when a candidate is excluded, the count is reset from the beginning (minus the excluded candidate).
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Other methods are supported, but not recommended:
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@ -88,6 +87,7 @@ Other surplus transfer methods, such as non-fractional transfers (e.g. random sa
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* Exclude in one round (default): When excluding a candidate, transfer all their ballot papers in one round.
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* Exclude by parcel (by order): When excluding a candidate, transfer their ballot papers one parcel at a time, in their order each was received. Each parcel forms a separate round, i.e. if a transfer allows another candidate to meet the quota criterion, no further papers are transferred to that candidate.
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* Exclude by value: When excluding a candidate, transfer their ballot papers in descending order of accumulated transfer value. Each transfer of all ballots of a certain transfer value forms a separate round.
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* Wright method (re-iterate): When a candidate is excluded, the count is reset from the beginning (minus the excluded candidate).
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## Ties (-t/--ties)
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@ -147,6 +147,7 @@
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<option value="parcels_by_order">Exclude by parcel (by order)</option>
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<!--<option value="parcels_by_value">Exclude by parcel (by value)</option>-->
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<option value="by_value">Exclude by value</option>
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<option value="wright">Wright method (re-iterate)</option>
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</select>
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</label>
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<br>
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@ -83,9 +83,9 @@ function changePreset() {
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document.getElementById('chkRoundVotes').checked = false;
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document.getElementById('chkRoundWeights').checked = false;
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document.getElementById('selSurplus').value = 'size';
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document.getElementById('selTransfers').value = 'wright';
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document.getElementById('selTransfers').value = 'wig';
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document.getElementById('selPapers').value = 'both';
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document.getElementById('selExclusion').value = 'one_round';
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document.getElementById('selExclusion').value = 'wright';
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document.getElementById('selTies').value = 'backwards_random';
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} else if (document.getElementById('selPreset').value === 'prsa77') {
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document.getElementById('selQuotaCriterion').value = 'geq';
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@ -46,8 +46,6 @@ onmessage = function(evt) {
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counter = py.pyRCV2.method.base_stv.UIGSTVCounter(election, evt.data.data.options);
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} else if (evt.data.data.transfers === 'eg') {
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counter = py.pyRCV2.method.base_stv.EGSTVCounter(election, evt.data.data.options);
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} else if (evt.data.data.transfers === 'wright') {
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counter = py.pyRCV2.method.wright.WrightSTVCounter(election, evt.data.data.options);
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} else {
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counter = py.pyRCV2.method.base_stv.WIGSTVCounter(election, evt.data.data.options);
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}
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@ -1,5 +1,5 @@
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# pyRCV2: Preferential vote counting
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# Copyright © 2020 Lee Yingtong Li (RunasSudo)
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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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@ -19,7 +19,6 @@ import pyRCV2.model
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import pyRCV2.numbers
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from pyRCV2.method.base_stv import UIGSTVCounter, WIGSTVCounter, EGSTVCounter
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from pyRCV2.method.wright import WrightSTVCounter
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from pyRCV2.ties import TiesBackwards, TiesPrompt, TiesRandom
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import sys
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@ -37,9 +36,9 @@ def add_parser(subparsers):
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parser.add_argument('--round-votes', type=int, help='round votes to specified decimal places')
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parser.add_argument('--round-weights', type=int, help='round ballot weights to specified decimal places')
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parser.add_argument('--surplus-order', '-s', choices=['size', 'order'], default='size', help='whether to distribute surpluses by size or by order of election (default: size)')
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parser.add_argument('--method', '-m', choices=['wig', 'uig', 'eg', 'wright'], default='wig', help='method of surpluses and exclusions (default: wig - weighted inclusive Gregory)')
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parser.add_argument('--method', '-m', choices=['wig', 'uig', 'eg'], default='wig', help='method of transferring surpluses (default: wig - weighted inclusive Gregory)')
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parser.add_argument('--transferable-only', action='store_true', help='examine only transferable papers during surplus distributions')
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parser.add_argument('--exclusion', choices=['one_round', 'parcels_by_order', 'by_value'], default='one_round', help='whether to perform exclusions in one round or parcel by parcel (default: one_round)')
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parser.add_argument('--exclusion', choices=['one_round', 'parcels_by_order', 'by_value', 'wright'], default='one_round', help='how to perform exclusions (default: one_round)')
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parser.add_argument('--ties', '-t', action='append', choices=['backwards', 'prompt', 'random'], default=None, help='how to resolve ties (default: backwards then random)')
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parser.add_argument('--random-seed', default=None, help='arbitrary string used to seed the RNG for random tie breaking')
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@ -85,8 +84,6 @@ def main(args):
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counter = UIGSTVCounter(election, vars(args))
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elif args.method == 'eg':
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counter = EGSTVCounter(election, vars(args))
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elif args.method == 'wright':
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counter = WrightSTVCounter(election, vars(args))
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else:
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counter = WIGSTVCounter(election, vars(args))
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@ -1,5 +1,5 @@
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# pyRCV2: Preferential vote counting
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# Copyright © 2020 Lee Yingtong Li (RunasSudo)
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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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@ -67,7 +67,7 @@ class BaseSTVCounter:
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'quota_criterion': 'geq', # 'geq' or 'gt'
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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' or 'by_value'
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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_votes': None, # Number of decimal places or None
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'round_weights': None, # Number of decimal places or None
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@ -315,6 +315,37 @@ class BaseSTVCounter:
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candidate_excluded, count_card = self.candidate_to_exclude()
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count_card.state = CandidateState.EXCLUDING
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# Handle Wright STV
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if self.options['exclusion'] == 'wright':
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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 ' + candidate_excluded.name
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return result
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# Exclude this candidate
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self.do_exclusion(candidate_excluded, count_card)
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@ -1,61 +0,0 @@
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# pyRCV2: Preferential vote counting
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# Copyright © 2020 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.method.base_stv import WIGSTVCounter
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from pyRCV2.model import CandidateState, CountCard
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from pyRCV2.safedict import SafeDict
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class WrightSTVCounter(WIGSTVCounter):
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"""
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Wright STV implementation
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"""
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def exclude_candidate(self):
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"""
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Overrides BaseSTVCounter.exclude_candidate per Wright STV
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"""
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candidate_excluded, count_card = self.candidate_to_exclude()
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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 ' + candidate_excluded.name
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return result
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@ -16,7 +16,7 @@
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import pyRCV2.blt
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import pyRCV2.model
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import pyRCV2.method, pyRCV2.method.base_stv, pyRCV2.method.wright
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import pyRCV2.method, pyRCV2.method.base_stv
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import pyRCV2.numbers
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import pyRCV2.random
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import pyRCV2.ties
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@ -1,5 +1,5 @@
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# pyRCV2: Preferential vote counting
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# Copyright © 2020 Lee Yingtong Li (RunasSudo)
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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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@ -17,7 +17,6 @@
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import pyRCV2.blt
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import pyRCV2.numbers
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import pyRCV2.method.base_stv
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import pyRCV2.method.wright
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from pyRCV2.model import CountCompleted
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import json
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@ -63,4 +62,4 @@ def maketst(numbers, counter_cls, options):
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test_prsa1_scottish_py, test_prsa1_scottish_js = maketst('Fixed', 'pyRCV2.method.base_stv.WIGSTVCounter', {})
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test_prsa1_stvc_py, test_prsa1_stvc_js = maketst('Rational', 'pyRCV2.method.base_stv.WIGSTVCounter', {'quota': 'droop_exact', 'quota_criterion': 'gt', 'prog_quota': True})
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test_prsa1_senate_py, test_prsa1_senate_js = maketst('Fixed', 'pyRCV2.method.base_stv.UIGSTVCounter', {'surplus_order': 'order', 'exclusion': 'by_value'})
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test_prsa1_wright_py, test_prsa1_wright_js = maketst('Fixed', 'pyRCV2.method.wright.WrightSTVCounter', {})
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test_prsa1_wright_py, test_prsa1_wright_js = maketst('Fixed', 'pyRCV2.method.base_stv.WIGSTVCounter', {'exclusion': 'wright'})
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@ -1,5 +1,5 @@
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# pyRCV2: Preferential vote counting
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# Copyright © 2020 Lee Yingtong Li (RunasSudo)
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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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@ -19,7 +19,7 @@ from pytest_steps import test_steps
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import pyRCV2.blt
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import pyRCV2.numbers
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from pyRCV2.method.wright import WrightSTVCounter
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from pyRCV2.method.base_stv import WIGSTVCounter
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from pyRCV2.model import CandidateState, CountCompleted
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def count_until_exclude(counter):
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@ -43,7 +43,7 @@ def test_csm15():
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cands = {c.name: c for c in election.candidates}
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counter = WrightSTVCounter(election)
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counter = WIGSTVCounter(election, {'exclusion': 'wright'})
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# Round 1
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result = counter.reset()
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