pyRCV2/tests/test_prsa.py

#   pyRCV2: Preferential vote counting
#   Copyright © 2020–2021  Lee Yingtong Li (RunasSudo)
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU Affero General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU Affero General Public License for more details.
#
#   You should have received a copy of the GNU Affero General Public License
#   along with this program.  If not, see <https://www.gnu.org/licenses/>.

import pyRCV2.blt
import pyRCV2.numbers
from pyRCV2.method.base_stv import EGSTVCounter
from pyRCV2.model import CandidateState, CountCompleted

def isclose(x, y):
	# There will be some discrepancy due to how the PRSA count rounds transfer values, so accept up to 0.1 votes difference
	return abs(int(x.impl) - y) < 100

def test_prsa1():
	"""Compare count of prsa1.blt with model result at http://www.prsa.org.au/example1.pdf"""
	
	pyRCV2.numbers.set_numclass(pyRCV2.numbers.Fixed)
	pyRCV2.numbers.set_dps(5)
	
	with open('tests/data/prsa1.blt', 'r') as f:
		election = pyRCV2.blt.readBLT(f.read())
	
	assert len(election.candidates) == 7
	
	c_evans = next(c for c in election.candidates if c.name == 'Evans')
	c_grey = next(c for c in election.candidates if c.name == 'Grey')
	c_thomson = next(c for c in election.candidates if c.name == 'Thomson')
	c_ames = next(c for c in election.candidates if c.name == 'Ames')
	c_reid = next(c for c in election.candidates if c.name == 'Reid')
	c_spears = next(c for c in election.candidates if c.name == 'Spears')
	c_white = next(c for c in election.candidates if c.name == 'White')
	
	counter = EGSTVCounter(election, {
		'surplus_order': 'order',
		'papers': 'transferable',
		'exclusion': 'parcels_by_order',
		'round_quota': 0,
	})
	
	# Stage 1
	result = counter.reset()
	assert len(result.candidates.impl) == 7
	assert int(result.total.impl) == 65000
	assert int(result.quota.impl) == 13001
	assert result.comment == 'First preferences'
	assert isclose(result.candidates[c_evans].votes, 1000)
	assert isclose(result.candidates[c_grey].votes, 34000)
	assert isclose(result.candidates[c_thomson].votes, 5000)
	assert isclose(result.candidates[c_ames].votes, 10000)
	assert isclose(result.candidates[c_reid].votes, 1000)
	assert isclose(result.candidates[c_spears].votes, 11000)
	assert isclose(result.candidates[c_white].votes, 3000)
	assert isclose(result.exhausted.votes, 0)
	
	# Stage 2
	result = counter.step()
	assert result.comment == 'Surplus of Grey'
	assert isclose(result.candidates[c_evans].votes, 2234)
	assert isclose(result.candidates[c_grey].votes, 13001)
	assert isclose(result.candidates[c_thomson].votes, 7468)
	assert isclose(result.candidates[c_ames].votes, 18638)
	assert isclose(result.candidates[c_reid].votes, 1617)
	assert isclose(result.candidates[c_spears].votes, 17170)
	assert isclose(result.candidates[c_white].votes, 4851)
	assert isclose(result.exhausted.votes, 0)
	
	# Stage 3
	result = counter.step()
	assert result.comment == 'Surplus of Ames'
	assert isclose(result.candidates[c_evans].votes, 3038)
	assert isclose(result.candidates[c_grey].votes, 13001)
	assert isclose(result.candidates[c_thomson].votes, 8674)
	assert isclose(result.candidates[c_ames].votes, 13001)
	assert isclose(result.candidates[c_reid].votes, 2019)
	assert isclose(result.candidates[c_spears].votes, 17170)
	assert isclose(result.candidates[c_white].votes, 8067)
	assert isclose(result.exhausted.votes, 0)
	
	# Stage 4
	result = counter.step()
	assert result.comment == 'Surplus of Spears'
	assert isclose(result.candidates[c_evans].votes, 4823)
	assert isclose(result.candidates[c_grey].votes, 13001)
	assert isclose(result.candidates[c_thomson].votes, 8674)
	assert isclose(result.candidates[c_ames].votes, 13001)
	assert isclose(result.candidates[c_reid].votes, 3804)
	assert isclose(result.candidates[c_spears].votes, 13001)
	assert isclose(result.candidates[c_white].votes, 8662)
	assert isclose(result.exhausted.votes, 0)
	
	# Stage 5
	result = counter.step()
	assert result.comment == 'Exclusion of Reid'
	assert isclose(result.candidates[c_reid].transfers, -1000)
	assert isclose(result.candidates[c_white].transfers, 1000)
	
	# Stage 6
	result = counter.step()
	assert result.comment == 'Exclusion of Reid'
	assert isclose(result.candidates[c_reid].transfers, -617)
	assert isclose(result.candidates[c_white].transfers, 617)
	
	# Stage 7
	result = counter.step()
	assert result.comment == 'Exclusion of Reid'
	assert isclose(result.candidates[c_reid].transfers, -402)
	assert isclose(result.candidates[c_evans].transfers, 402)
	
	# Stage 8
	result = counter.step()
	assert result.comment == 'Exclusion of Reid'
	assert isclose(result.candidates[c_reid].transfers, -1785)
	assert isclose(result.candidates[c_evans].transfers, 595)
	assert isclose(result.candidates[c_thomson].transfers, 1190)
	
	assert isclose(result.candidates[c_evans].votes, 5820)
	assert isclose(result.candidates[c_grey].votes, 13001)
	assert isclose(result.candidates[c_thomson].votes, 9864)
	assert isclose(result.candidates[c_ames].votes, 13001)
	assert isclose(result.candidates[c_reid].votes, 0)
	assert isclose(result.candidates[c_spears].votes, 13001)
	assert isclose(result.candidates[c_white].votes, 10279)
	assert isclose(result.exhausted.votes, 0)
	
	# Stage 9
	result = counter.step()
	assert result.comment == 'Exclusion of Evans'
	assert isclose(result.candidates[c_evans].transfers, -1000)
	assert isclose(result.candidates[c_thomson].transfers, 1000)
	
	# Stage 10
	result = counter.step()
	assert result.comment == 'Exclusion of Evans'
	assert isclose(result.candidates[c_evans].transfers, -1234)
	assert isclose(result.exhausted.transfers, 1234)
	
	# Stage 11
	result = counter.step()
	assert result.comment == 'Exclusion of Evans'
	assert isclose(result.candidates[c_evans].transfers, -804)
	assert isclose(result.candidates[c_thomson].transfers, 402)
	assert isclose(result.candidates[c_white].transfers, 402)
	
	# Stage 12
	result = counter.step()
	assert result.comment == 'Exclusion of Evans'
	assert isclose(result.candidates[c_evans].transfers, -1785)
	assert isclose(result.candidates[c_white].transfers, 1190)
	assert isclose(result.exhausted.transfers, 595)
	
	# Stage 13
	result = counter.step()
	assert result.comment == 'Exclusion of Evans'
	assert isclose(result.candidates[c_evans].transfers, -402)
	assert isclose(result.candidates[c_thomson].transfers, 402)
	
	# Stage 14
	result = counter.step()
	assert result.comment == 'Exclusion of Evans'
	assert isclose(result.candidates[c_evans].transfers, -595)
	assert isclose(result.candidates[c_white].transfers, 595)
	
	assert isclose(result.candidates[c_evans].votes, 0)
	assert isclose(result.candidates[c_grey].votes, 13001)
	assert isclose(result.candidates[c_thomson].votes, 11668)
	assert isclose(result.candidates[c_ames].votes, 13001)
	assert isclose(result.candidates[c_reid].votes, 0)
	assert isclose(result.candidates[c_spears].votes, 13001)
	assert isclose(result.candidates[c_white].votes, 12466)
	assert isclose(result.exhausted.votes, 1829)
	
	# Stage 15
	result = counter.step()
	assert result.comment == 'Exclusion of Thomson'
	assert isclose(result.candidates[c_thomson].transfers, -5000)
	assert isclose(result.exhausted.transfers, 5000)
	
	# Stage 16
	result = counter.step()
	assert result.comment == 'Exclusion of Thomson'
	assert isclose(result.candidates[c_thomson].transfers, -2468)
	assert isclose(result.exhausted.transfers, 2468)
	
	# Stage 17
	result = counter.step()
	assert result.comment == 'Exclusion of Thomson'
	assert isclose(result.candidates[c_thomson].transfers, -1206)
	assert isclose(result.candidates[c_white].transfers, 1206)
	
	assert isclose(result.candidates[c_evans].votes, 0)
	assert isclose(result.candidates[c_grey].votes, 13001)
	assert isclose(result.candidates[c_thomson].votes, 2994)
	assert isclose(result.candidates[c_ames].votes, 13001)
	assert isclose(result.candidates[c_reid].votes, 0)
	assert isclose(result.candidates[c_spears].votes, 13001)
	assert isclose(result.candidates[c_white].votes, 13672)
	assert isclose(result.exhausted.votes, 9297)
	
	assert result.candidates[c_evans].state == CandidateState.EXCLUDED
	assert result.candidates[c_grey].state == CandidateState.ELECTED
	assert result.candidates[c_thomson].state == CandidateState.EXCLUDING
	assert result.candidates[c_ames].state == CandidateState.ELECTED
	assert result.candidates[c_reid].state == CandidateState.EXCLUDED
	assert result.candidates[c_spears].state == CandidateState.ELECTED
	assert result.candidates[c_white].state == CandidateState.PROVISIONALLY_ELECTED
	
	# Count complete
	result = counter.step()
	assert isinstance(result, CountCompleted)