185 lines
9.1 KiB
Python
185 lines
9.1 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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import pyRCV2.blt, pyRCV2.con
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import pyRCV2.model
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import pyRCV2.numbers
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from pyRCV2.method.gregory import UIGSTVCounter, WIGSTVCounter, EGSTVCounter
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from pyRCV2.method.meek import MeekSTVCounter
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from pyRCV2.model import CandidateState
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from pyRCV2.ties import TiesBackwards, TiesForwards, TiesPrompt, TiesRandom
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import sys
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def add_parser(subparsers):
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parser = subparsers.add_parser('stv', help='single transferable vote')
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parser.add_argument('file', help='path to BLT file')
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parser.add_argument('--quota', '-q', choices=['droop', 'droop_exact', 'hare', 'hare_exact'], default='droop', help='quota calculation (default: droop)')
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parser.add_argument('--quota-criterion', '-c', choices=['geq', 'gt'], default='geq', help='quota criterion (default: geq)')
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parser.add_argument('--quota-mode', choices=['static', 'progressive', 'ers97'], default='static', help='whether to apply a form of progressive quota (default: static)')
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parser.add_argument('--no-bulk-elect', action='store_true', help='disable bulk election unless absolutely required')
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parser.add_argument('--bulk-exclude', action='store_true', help='use bulk exclusion')
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parser.add_argument('--defer-surpluses', action='store_true', help='defer surplus transfers if possible')
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parser.add_argument('--numbers', '-n', choices=['fixed', 'gfixed', 'rational', 'native'], default='fixed', help='numbers mode (default: fixed)')
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parser.add_argument('--decimals', type=int, default=5, help='decimal places if --numbers fixed (default: 5)')
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parser.add_argument('--round-quota', type=int, help='round quota to specified decimal places')
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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-tvs', type=int, help='round transfer values 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', 'meek'], 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', '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', 'forwards', 'prompt', 'random'], default=None, help='how to resolve ties (default: prompt)')
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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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parser.add_argument('--constraints', default=None, help='CON file specifying constraints for the election')
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#parser.add_argument('--constraint-mode', choices=['matrix', 'guarding'], default=None, help='mode of dealing with constraints (default: matrix)')
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parser.add_argument('--hide-excluded', action='store_true', help='hide excluded candidates from results report')
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parser.add_argument('--sort-votes', action='store_true', help='sort candidates by votes in results report')
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parser.add_argument('--pp-decimals', type=int, default=2, help='print votes to specified decimal places in results report (default: 2)')
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def print_step(args, stage, result):
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if result.stage_kind:
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print('{}. {} {}'.format(stage, result.stage_kind, result.comment))
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else:
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print('{}. {}'.format(stage, result.comment))
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if result.logs:
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print(' '.join(result.logs))
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results = list(result.candidates.items())
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if args.sort_votes:
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results.sort(key=lambda x: x[1].votes, reverse=True)
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for candidate, count_card in results:
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state = None
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if count_card.state == pyRCV2.model.CandidateState.ELECTED or count_card.state == pyRCV2.model.CandidateState.PROVISIONALLY_ELECTED or count_card.state == pyRCV2.model.CandidateState.DISTRIBUTING_SURPLUS:
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if args.method == 'meek':
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state = 'ELECTED {} (kv = {})'.format(count_card.order_elected, count_card.keep_value.pp(args.pp_decimals))
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else:
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state = 'ELECTED {}'.format(count_card.order_elected)
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elif count_card.state == pyRCV2.model.CandidateState.EXCLUDED or count_card.state == pyRCV2.model.CandidateState.EXCLUDING:
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state = 'Excluded {}'.format(-count_card.order_elected)
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elif count_card.state == pyRCV2.model.CandidateState.DOOMED:
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state = 'Doomed'
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elif count_card.state == pyRCV2.model.CandidateState.GUARDED:
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state = 'Guarded'
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elif count_card.state == pyRCV2.model.CandidateState.WITHDRAWN:
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state = 'Withdrawn'
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ppVotes = count_card.votes.pp(args.pp_decimals)
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ppTransfers = count_card.transfers.pp(args.pp_decimals)
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if state is None:
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print('- {}: {} ({})'.format(candidate.name, ppVotes, ppTransfers))
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else:
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if not (args.hide_excluded and (count_card.state == pyRCV2.model.CandidateState.EXCLUDED or count_card.state == pyRCV2.model.CandidateState.EXCLUDING) and float(ppVotes) == 0 and float(ppTransfers) == 0):
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print('- {}: {} ({}) - {}'.format(candidate.name, ppVotes, ppTransfers, state))
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print('Exhausted: {} ({})'.format(result.exhausted.votes.pp(args.pp_decimals), result.exhausted.transfers.pp(args.pp_decimals)))
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print('Loss to fraction: {} ({})'.format(result.loss_fraction.votes.pp(args.pp_decimals), result.loss_fraction.transfers.pp(args.pp_decimals)))
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print('Total votes: {}'.format(result.total.pp(args.pp_decimals)))
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if args.quota_mode == 'ers97' and result.vote_required_election < result.quota:
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print('Vote required for election: {}'.format(result.vote_required_election.pp(args.pp_decimals)))
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else:
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print('Quota: {}'.format(result.quota.pp(args.pp_decimals)))
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print()
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def main(args):
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# Set settings
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if args.numbers == 'native':
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pyRCV2.numbers.set_numclass(pyRCV2.numbers.Native)
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elif args.numbers == 'rational':
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pyRCV2.numbers.set_numclass(pyRCV2.numbers.Rational)
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elif args.numbers == 'fixed':
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pyRCV2.numbers.set_numclass(pyRCV2.numbers.Fixed)
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pyRCV2.numbers.set_dps(args.decimals)
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elif args.numbers == 'gfixed':
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pyRCV2.numbers.set_numclass(pyRCV2.numbers.FixedGuarded)
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pyRCV2.numbers.set_dps(args.decimals)
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with open(args.file, 'r') as f:
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election = pyRCV2.blt.readBLT(f.read())
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# Create counter
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if args.method == 'uig':
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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 == 'meek':
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counter = MeekSTVCounter(election, vars(args))
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else:
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counter = WIGSTVCounter(election, vars(args))
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if args.ties is None:
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args.ties = ['prompt']
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counter.options['ties'] = []
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for t in args.ties:
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if t == 'backwards':
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counter.options['ties'].append(TiesBackwards(counter))
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elif t == 'forwards':
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counter.options['ties'].append(TiesForwards(counter))
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elif t == 'prompt':
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counter.options['ties'].append(TiesPrompt())
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elif t == 'random':
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if args.random_seed is None:
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print('A --random-seed is required to use random tie breaking.')
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sys.exit(1)
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counter.options['ties'].append(TiesRandom(args.random_seed))
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counter.options['bulk_elect'] = not args.no_bulk_elect
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counter.options['papers'] = 'transferable' if args.transferable_only else 'both'
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if args.constraints is not None:
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with open(args.constraints, 'r') as f:
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election.constraints = pyRCV2.con.readCON(f.read(), election)
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# Print report
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print('Count computed by pyRCV2 (development version). Read {} ballots from "{}" for election "{}". There are {} candidates for {} vacancies. Counting using options "{}".'.format(sum((b.value for b in election.ballots), pyRCV2.numbers.Num(0)).pp(0), args.file, election.name, len(election.candidates), election.seats, counter.describe_options()))
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print()
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# Reset
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stage = 1
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result = counter.reset()
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print_step(args, stage, result)
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# Step election
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while True:
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stage += 1
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result = counter.step()
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if isinstance(result, pyRCV2.model.CountCompleted):
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break
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print_step(args, stage, result)
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print('Count complete. The winning candidates are, in order of election:')
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for x in sorted(((c, cc) for c, cc in result.candidates.items() if cc.state == CandidateState.PROVISIONALLY_ELECTED or cc.state == CandidateState.DISTRIBUTING_SURPLUS or cc.state == CandidateState.ELECTED), key=lambda x: x[1].order_elected):
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print('{}. {}'.format(x[1].order_elected , x[0].name))
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