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Optimise next_preferences algorithm to avoid re-examining earlier preferences

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Senate count from 9.02 to 8.22s
This commit is contained in:
RunasSudo 2021-01-19 02:14:59 +11:00
parent ad35b63d8f
commit 53657677a3
Signed by: RunasSudo
GPG Key ID: 7234E476BF21C61A
4 changed files with 75 additions and 49 deletions
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51
pyRCV2/method/base_stv.py
View File

@ -16,7 +16,7 @@
__pragma__ = lambda x: None
from pyRCV2.model import CandidateState, CountCard, CountCompleted, CountStepResult
from pyRCV2.model import BallotInCount, CandidateState, CountCard, CountCompleted, CountStepResult
import pyRCV2.numbers
from pyRCV2.numbers import Num
from pyRCV2.safedict import SafeDict
@ -101,15 +101,18 @@ class BaseSTVCounter:
for ballot in self.election.ballots:
__pragma__('opov')
candidate = next((c for c in ballot.preferences if self.candidates[c].state == CandidateState.HOPEFUL), None)
if candidate is not None:
self.candidates[candidate].transfers += ballot.value
if len(self.candidates[candidate].parcels) == 0:
self.candidates[candidate].parcels.append([(ballot, Num(ballot.value))])
else:
self.candidates[candidate].parcels[0].append((ballot, Num(ballot.value)))
for i, candidate in enumerate(ballot.preferences):
count_card = self.candidates[candidate]
if count_card.state == CandidateState.HOPEFUL:
count_card.transfers += ballot.value
if len(count_card.parcels) == 0:
count_card.parcels.append([BallotInCount(ballot, Num(ballot.value), i)])
else:
count_card.parcels[0].append(BallotInCount(ballot, Num(ballot.value), i))
break
else:
# No available preference
self.exhausted.transfers += ballot.value
#self.exhausted.parcels[0].append((ballot, Num(ballot.value)))
__pragma__('noopov')
@ -601,7 +604,7 @@ class BaseSTVCounter:
"""
Examine the specified ballots and group ballot papers by next available preference
"""
# SafeDict: Candidate -> [List[Ballot], ballots, votes]
# SafeDict: Candidate -> [List[BallotInCount], 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')
@ -611,21 +614,25 @@ class BaseSTVCounter:
exhausted_votes = Num('0')
for parcel in parcels:
for ballot, ballot_value in parcel:
for bc 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)
total_ballots += bc.ballot.value
total_votes += bc.ballot_value
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
for i in range(bc.last_preference + 1, len(bc.ballot.preferences)):
candidate = bc.ballot.preferences[i]
count_card = self.candidates[candidate]
if count_card.state == CandidateState.HOPEFUL:
next_preferences[candidate][0].append(BallotInCount(bc.ballot, bc.ballot_value, i))
next_preferences[candidate][1] += bc.ballot.value
next_preferences[candidate][2] += bc.ballot_value
break
else:
next_exhausted.append((ballot, ballot_value))
exhausted_ballots += ballot.value
exhausted_votes += ballot_value
# No next available preference
next_exhausted.append(bc)
exhausted_ballots += bc.ballot.value
exhausted_votes += bc.ballot_value
__pragma__('noopov')
return next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes

53
pyRCV2/method/gregory.py
View File

@ -119,37 +119,38 @@ class BaseGregorySTVCounter(BaseSTVCounter):
self.candidates[candidate].transfers += self.round_votes(num_units * tv)
__pragma__('noopov')
for ballot, ballot_value in cand_ballots:
for bc in cand_ballots:
__pragma__('opov')
if self.options['papers'] == 'transferable':
if transferable_votes > surplus:
if self.options['round_tvs'] is None:
if is_weighted:
new_value = (ballot_value * surplus) / transferable_units
new_value = (bc.ballot_value * surplus) / transferable_units
else:
new_value = (ballot.value * surplus) / transferable_units
new_value = (bc.ballot.value * surplus) / transferable_units
else:
tv = self.round_tv(surplus / transferable_units)
if is_weighted:
new_value = ballot_value * tv
new_value = bc.ballot_value * tv
else:
new_value = ballot.value * tv
new_value = bc.ballot.value * tv
else:
new_value = ballot_value
new_value = bc.ballot_value
else:
if self.options['round_tvs'] is None:
if is_weighted:
new_value = (ballot_value * surplus) / total_units
new_value = (bc.ballot_value * surplus) / total_units
else:
new_value = (ballot.value * surplus) / total_units
new_value = (bc.ballot.value * surplus) / total_units
else:
tv = self.round_tv(surplus / total_units)
if is_weighted:
new_value = ballot_value * tv
new_value = bc.ballot_value * tv
else:
new_value = ballot.value * tv
new_value = bc.ballot.value * tv
new_parcel.append((ballot, self.round_weight(new_value)))
bc.ballot_value = self.round_weight(new_value)
new_parcel.append(bc)
__pragma__('noopov')
__pragma__('opov')
@ -174,29 +175,29 @@ class BaseGregorySTVCounter(BaseSTVCounter):
def do_exclusion(self, candidates_excluded):
"""Implements BaseSTVCounter.do_exclusion"""
# Optimisation: Pre-sort exclusion ballots if applicable
# self._exclusion[1] -> list of ballots-per-stage, ballots-per-stage = List[Tuple[Candidate,List[Ballot+Value]]]
# self._exclusion[1] -> list of ballots-per-stage ; ballots-per-stage = List[Tuple[Candidate,List[BallotInCount]]]
if self._exclusion is None:
if self.options['exclusion'] == 'one_round':
self._exclusion = (candidates_excluded, [[(c, [b for p in cc.parcels for b in p]) for c, cc in candidates_excluded]])
self._exclusion = (candidates_excluded, [[(c, [bc for p in cc.parcels for bc in p]) for c, cc in candidates_excluded]])
elif self.options['exclusion'] == 'parcels_by_order':
c, cc = candidates_excluded[0]
self._exclusion = (candidates_excluded, [[(c, p)] for p in cc.parcels])
elif self.options['exclusion'] == 'by_value':
ballots = [(c, b, bv) for c, cc in candidates_excluded for p in cc.parcels for b, bv in p]
ballots = [(c, bc) for c, cc in candidates_excluded for p in cc.parcels for bc in p]
# Sort ballots by value
__pragma__('opov')
ballots.sort(key=lambda x: x[2] / x[1].value, reverse=True)
# Round to 8 decimal places to consider equality
# FIXME: Work out a better way of doing this
ballots.sort(key=lambda x: x[1].ballot_value / x[1].ballot.value, reverse=True)
if self.options['round_tvs']:
ballots_by_value = groupby(ballots, lambda x: self.round_tv(x[2] / x[1].value))
ballots_by_value = groupby(ballots, lambda x: self.round_tv(x[1].ballot_value / x[1].ballot.value))
else:
ballots_by_value = groupby(ballots, lambda x: (x[2] / x[1].value).round(8, x[2].ROUND_DOWN))
# Round to 8 decimal places to consider equality
# FIXME: Work out a better way of doing this
ballots_by_value = groupby(ballots, lambda x: (x[1].ballot_value / x[1].ballot.value).round(8, x[1].ballot_value.ROUND_DOWN))
__pragma__('noopov')
# TODO: Can we combine ballots for each candidate within each stage?
self._exclusion = (candidates_excluded, [[(c, [(b, bv)]) for c, b, bv in x] for x in ballots_by_value])
self._exclusion = (candidates_excluded, [[(c, [bc]) for c, bc in x] for x in ballots_by_value])
else:
raise STVException('Invalid exclusion mode') # pragma: no cover
@ -205,11 +206,11 @@ class BaseGregorySTVCounter(BaseSTVCounter):
# Transfer votes
next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes = self.next_preferences([bb for c, bb in this_exclusion])
next_preferences, total_ballots, total_votes, next_exhausted, exhausted_ballots, exhausted_votes = self.next_preferences([bc for c, bc in this_exclusion])
if self.options['exclusion'] != 'one_round':
__pragma__('opov')
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) + '.')
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) + '.')
__pragma__('noopov')
for candidate, x in next_preferences.items():
@ -225,9 +226,9 @@ class BaseGregorySTVCounter(BaseSTVCounter):
self.candidates[candidate].transfers += self.round_votes(num_votes)
__pragma__('noopov')
for ballot, ballot_value in cand_ballots:
for bc in cand_ballots:
__pragma__('opov')
new_parcel.append((ballot, ballot_value))
new_parcel.append(bc)
__pragma__('noopov')
# Subtract votes
@ -238,9 +239,9 @@ class BaseGregorySTVCounter(BaseSTVCounter):
for candidate, ballots in this_exclusion:
total_votes = Num(0)
for ballot, ballot_value in ballots:
for bc in ballots:
__pragma__('opov')
total_votes += ballot_value
total_votes += bc.ballot_value
__pragma__('noopov')
__pragma__('opov')

2
pyRCV2/method/meek.py
View File

@ -33,7 +33,7 @@ class MeekCountCard(CountCard):
result = MeekCountCard()
result.orig_votes = self.orig_votes
result.transfers = self.transfers
result.parcels = [[(b[0].clone(), b[1]) for b in p] for p in self.parcels]
#result.parcels = [[(b[0].clone(), b[1]) for b in p] for p in self.parcels]
result.state = self.state
result.order_elected = self.order_elected
result.keep_value = keep_value

18
pyRCV2/model.py
View File

@ -38,6 +38,10 @@ class CandidateState:
WITHDRAWN = 60
class Ballot:
"""
Represents a voter's (or if weighted, multiple voters') preferences
"""
def __init__(self, value, preferences):
self.value = value
self.preferences = preferences
@ -45,6 +49,20 @@ class Ballot:
def clone(self):
return Ballot(self.value, self.preferences)
class BallotInCount:
"""
Represents a Ballot held by a candidate at a particular value during the count
"""
__slots__ = ['ballot', 'ballot_value', 'last_preference']
def __init__(self, ballot, ballot_value, last_preference):
self.ballot = ballot
self.ballot_value = ballot_value
# Optimisation: Record the most-recently used preference so earlier preferences do not need to be later examined
self.last_preference = last_preference
class Election:
"""
Represents a BLT election