778 lines
27 KiB
Rust
778 lines
27 KiB
Rust
/* OpenTally: Open-source election vote counting
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* Copyright © 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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*/
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use super::{ExclusionMethod, NextPreferencesEntry, STVError, STVOptions, SumSurplusTransfersMode, SurplusMethod, SurplusOrder};
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use super::sample;
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use crate::constraints;
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use crate::election::{Candidate, CandidateState, CountState, Parcel, Vote};
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use crate::numbers::Number;
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use crate::ties;
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use std::cmp::max;
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use std::collections::HashMap;
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use std::ops;
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/// Distribute first preference votes according to the Gregory method
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pub fn distribute_first_preferences<N: Number>(state: &mut CountState<N>) {
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let votes = state.election.ballots.iter().map(|b| Vote {
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ballot: b,
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up_to_pref: 0,
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}).collect();
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let result = super::next_preferences(state, votes);
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// Transfer candidate votes
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for (candidate, entry) in result.candidates.into_iter() {
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let parcel = Parcel {
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votes: entry.votes,
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value_fraction: N::one(),
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source_order: 0,
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};
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let count_card = state.candidates.get_mut(candidate).unwrap();
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count_card.parcels.push(parcel);
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count_card.transfer(&entry.num_ballots);
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count_card.ballot_transfers += entry.num_ballots;
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}
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// Transfer exhausted votes
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let parcel = Parcel {
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votes: result.exhausted.votes,
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value_fraction: N::one(),
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source_order: 0,
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};
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state.exhausted.parcels.push(parcel);
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state.exhausted.transfer(&result.exhausted.num_ballots);
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state.exhausted.ballot_transfers += result.exhausted.num_ballots;
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state.kind = None;
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state.title = "First preferences".to_string();
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state.logger.log_literal("First preferences distributed.".to_string());
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}
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/// Distribute the largest surplus according to the Gregory or random subset method, based on [STVOptions::surplus]
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///
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/// Returns `true` if any surpluses were distributed.
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pub fn distribute_surpluses<N: Number>(state: &mut CountState<N>, opts: &STVOptions) -> Result<bool, STVError>
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where
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for<'r> &'r N: ops::Add<&'r N, Output=N>,
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for<'r> &'r N: ops::Sub<&'r N, Output=N>,
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for<'r> &'r N: ops::Mul<&'r N, Output=N>,
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for<'r> &'r N: ops::Div<&'r N, Output=N>,
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for<'r> &'r N: ops::Neg<Output=N>
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{
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let quota = state.quota.as_ref().unwrap();
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let has_surplus: Vec<&Candidate> = state.election.candidates.iter() // Present in order in case of tie
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.filter(|c| {
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let cc = &state.candidates[c];
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&cc.votes > quota && !cc.finalised
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})
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.collect();
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if !has_surplus.is_empty() {
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let total_surpluses = has_surplus.iter()
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.fold(N::new(), |acc, c| acc + &state.candidates[c].votes - quota);
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// Determine if surplues can be deferred
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if opts.defer_surpluses {
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if super::can_defer_surpluses(state, opts, &total_surpluses) {
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state.logger.log_literal(format!("Distribution of surpluses totalling {:.dps$} votes will be deferred.", total_surpluses, dps=opts.pp_decimals));
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return Ok(false);
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}
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}
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// Distribute top candidate's surplus
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let max_cands = match opts.surplus_order {
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SurplusOrder::BySize => {
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ties::multiple_max_by(&has_surplus, |c| &state.candidates[c].votes)
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}
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SurplusOrder::ByOrder => {
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ties::multiple_min_by(&has_surplus, |c| state.candidates[c].order_elected)
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}
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};
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let elected_candidate = if max_cands.len() > 1 {
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super::choose_highest(state, opts, max_cands, "Which candidate's surplus to distribute?")?
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} else {
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max_cands[0]
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};
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// If --no-immediate-elect, declare elected the candidate with the highest surplus
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if !opts.immediate_elect {
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let count_card = state.candidates.get_mut(elected_candidate).unwrap();
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count_card.state = CandidateState::Elected;
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state.num_elected += 1;
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count_card.order_elected = state.num_elected as isize;
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state.logger.log_smart(
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"{} meets the quota and is elected.",
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"{} meet the quota and are elected.",
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vec![&elected_candidate.name]
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);
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constraints::update_constraints(state, opts);
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}
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match opts.surplus {
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SurplusMethod::WIG | SurplusMethod::UIG | SurplusMethod::EG => { distribute_surplus(state, &opts, elected_candidate); }
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SurplusMethod::Cincinnati | SurplusMethod::Hare => { sample::distribute_surplus(state, &opts, elected_candidate)?; }
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_ => unreachable!()
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}
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return Ok(true);
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}
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// If --no-immediate-elect, check for candidates with exactly a quota to elect
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// However, if --defer-surpluses, zero surplus is necessarily deferred so skip
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if !opts.immediate_elect && !opts.defer_surpluses {
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if super::elect_hopefuls(state, opts, false)? {
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return Ok(true);
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}
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}
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return Ok(false);
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}
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/// Return the denominator of the surplus fraction
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///
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/// Returns `None` if the value of transferable votes <= surplus (i.e. all transferable votes are transferred at values received).
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fn calculate_surplus_denom<'n, N: Number>(surplus: &N, transferable_ballots: &'n N, transferable_votes: &'n N, total_ballots: &'n N, total_votes: &'n N, weighted: bool, transferable_only: bool) -> Option<&'n N>
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where
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for<'r> &'r N: ops::Sub<&'r N, Output=N>
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{
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if transferable_only {
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let transferable_units = if weighted { transferable_votes } else { transferable_ballots };
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if transferable_votes > surplus {
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return Some(transferable_units);
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} else {
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return None;
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}
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} else {
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if weighted {
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return Some(total_votes);
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} else {
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return Some(total_ballots);
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}
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}
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}
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/// Return the reweighted value fraction of a parcel/vote after being transferred
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fn reweight_value_fraction<N: Number>(
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value_fraction: &N,
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surplus: &N,
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weighted: bool,
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surplus_fraction: &Option<N>,
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surplus_denom: &Option<&N>,
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round_tvs: Option<usize>) -> N
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{
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let result;
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match surplus_denom {
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Some(v) => {
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if let Some(_) = round_tvs {
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// Rounding requested: use the rounded transfer value
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if weighted {
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result = value_fraction.clone() * surplus_fraction.as_ref().unwrap();
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} else {
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result = surplus_fraction.as_ref().unwrap().clone();
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}
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} else {
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// Avoid unnecessary rounding error by first multiplying by the surplus
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if weighted {
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result = value_fraction.clone() * surplus / *v;
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} else {
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result = surplus.clone() / *v;
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}
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}
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}
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None => {
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result = value_fraction.clone();
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}
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}
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return result;
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}
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/// Compute the number of votes to credit to a continuing candidate during a surplus transfer, based on [STVOptions::sum_surplus_transfers]
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fn sum_surplus_transfers<N: Number>(entry: &NextPreferencesEntry<N>, orig_value_fraction: &N, surplus: &N, is_weighted: bool, surplus_fraction: &Option<N>, surplus_denom: &Option<&N>, _state: &mut CountState<N>, opts: &STVOptions) -> N
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where
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for<'r> &'r N: ops::Mul<&'r N, Output=N>,
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for<'r> &'r N: ops::Div<&'r N, Output=N>,
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{
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match opts.sum_surplus_transfers {
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SumSurplusTransfersMode::ByValue => {
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// Calculate transfer across all votes in this parcel
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let mut result = N::new();
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for vote in entry.votes.iter() {
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result += &vote.ballot.orig_value;
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}
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result *= reweight_value_fraction(orig_value_fraction, surplus, is_weighted, surplus_fraction, surplus_denom, opts.round_surplus_fractions);
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return result;
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}
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SumSurplusTransfersMode::PerBallot => {
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// Sum transfer per each individual ballot
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// TODO: This could be moved to distribute_surplus to avoid looping over the votes and calculating transfer values twice
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let mut new_value_fraction = reweight_value_fraction(orig_value_fraction, surplus, is_weighted, surplus_fraction, surplus_denom, opts.round_surplus_fractions);
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if let Some(dps) = opts.round_votes {
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new_value_fraction.floor_mut(dps);
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}
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let mut result = N::new();
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for vote in entry.votes.iter() {
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let mut vote_value = &new_value_fraction * &vote.ballot.orig_value;
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if let Some(dps) = opts.round_votes {
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vote_value.floor_mut(dps);
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}
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result += vote_value;
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}
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return result;
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}
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}
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}
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/// Distribute the surplus of a given candidate according to the Gregory method, based on [STVOptions::surplus]
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fn distribute_surplus<N: Number>(state: &mut CountState<N>, opts: &STVOptions, elected_candidate: &Candidate)
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where
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for<'r> &'r N: ops::Add<&'r N, Output=N>,
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for<'r> &'r N: ops::Sub<&'r N, Output=N>,
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for<'r> &'r N: ops::Mul<&'r N, Output=N>,
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for<'r> &'r N: ops::Div<&'r N, Output=N>,
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for<'r> &'r N: ops::Neg<Output=N>
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{
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state.kind = Some("Surplus of");
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state.title = String::from(&elected_candidate.name);
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state.logger.log_literal(format!("Surplus of {} distributed.", elected_candidate.name));
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let count_card = &state.candidates[elected_candidate];
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let surplus = &count_card.votes - state.quota.as_ref().unwrap();
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// Determine which votes to examine
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let mut parcels;
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match opts.surplus {
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SurplusMethod::WIG | SurplusMethod::UIG => {
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// Inclusive Gregory
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parcels = Vec::new();
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parcels.append(&mut state.candidates.get_mut(elected_candidate).unwrap().parcels);
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}
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SurplusMethod::EG => {
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// Exclusive Gregory
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// Should be safe to unwrap() - or else how did we get a quota!
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parcels = vec![state.candidates.get_mut(elected_candidate).unwrap().parcels.pop().unwrap()];
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}
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_ => unreachable!()
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}
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// Count votes
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let mut parcels_next_prefs= Vec::new();
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let mut transferable_ballots = N::new();
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let mut transferable_votes = N::new();
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let mut exhausted_ballots = N::new();
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let mut exhausted_votes = N::new();
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for parcel in parcels {
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// Count next preferences
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let result = super::next_preferences(state, parcel.votes);
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for (_, entry) in result.candidates.iter() {
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transferable_ballots += &entry.num_ballots;
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transferable_votes += &entry.num_ballots * &parcel.value_fraction;
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}
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exhausted_ballots += &result.exhausted.num_ballots;
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exhausted_votes += &result.exhausted.num_ballots * &parcel.value_fraction;
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parcels_next_prefs.push((parcel.value_fraction, result));
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}
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// Calculate surplus fraction
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let is_weighted = match opts.surplus {
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SurplusMethod::WIG => { true }
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SurplusMethod::UIG | SurplusMethod::EG => { false }
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_ => unreachable!()
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};
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let total_ballots = &transferable_ballots + &exhausted_ballots;
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let total_votes = &transferable_votes + &exhausted_votes;
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let count_card = state.candidates.get_mut(elected_candidate).unwrap();
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count_card.ballot_transfers = -&total_ballots;
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let surplus_denom = calculate_surplus_denom(&surplus, &transferable_ballots, &transferable_votes, &total_ballots, &total_votes, is_weighted, opts.transferable_only);
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let mut surplus_fraction;
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match surplus_denom {
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Some(v) => {
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surplus_fraction = Some(surplus.clone() / v);
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// Round down if requested
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if let Some(dps) = opts.round_surplus_fractions {
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surplus_fraction.as_mut().unwrap().floor_mut(dps);
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}
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if opts.transferable_only {
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if transferable_ballots == N::one() {
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state.logger.log_literal(format!("Transferring 1 transferable ballot, totalling {:.dps$} transferable votes, with surplus fraction {:.dps2$}.", transferable_votes, surplus_fraction.as_ref().unwrap(), dps=opts.pp_decimals, dps2=max(opts.pp_decimals, 2)));
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} else {
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state.logger.log_literal(format!("Transferring {:.0} transferable ballots, totalling {:.dps$} transferable votes, with surplus fraction {:.dps2$}.", transferable_ballots, transferable_votes, surplus_fraction.as_ref().unwrap(), dps=opts.pp_decimals, dps2=max(opts.pp_decimals, 2)));
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}
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} else {
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if total_ballots == N::one() {
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state.logger.log_literal(format!("Transferring 1 ballot, totalling {:.dps$} votes, with surplus fraction {:.dps2$}.", total_votes, surplus_fraction.as_ref().unwrap(), dps=opts.pp_decimals, dps2=max(opts.pp_decimals, 2)));
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} else {
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state.logger.log_literal(format!("Transferring {:.0} ballots, totalling {:.dps$} votes, with surplus fraction {:.dps2$}.", total_ballots, total_votes, surplus_fraction.as_ref().unwrap(), dps=opts.pp_decimals, dps2=max(opts.pp_decimals, 2)));
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}
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}
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}
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None => {
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surplus_fraction = None;
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// This can only happen if --transferable-only
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if transferable_ballots == N::one() {
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state.logger.log_literal(format!("Transferring 1 transferable ballot, totalling {:.dps$} transferable votes, at values received.", transferable_votes, dps=opts.pp_decimals));
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} else {
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state.logger.log_literal(format!("Transferring {:.0} transferable ballots, totalling {:.dps$} transferable votes, at values received.", transferable_ballots, transferable_votes, dps=opts.pp_decimals));
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}
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}
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}
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// Reweight and transfer parcels
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let mut candidate_transfers: HashMap<&Candidate, N> = HashMap::new();
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for candidate in state.election.candidates.iter() {
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candidate_transfers.insert(candidate, N::new());
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}
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let mut exhausted_transfers = N::new();
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for (value_fraction, result) in parcels_next_prefs {
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for (candidate, entry) in result.candidates.into_iter() {
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// Record transfers
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// TODO: Is there a better way of writing this?
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let transfers_orig = candidate_transfers.remove(candidate).unwrap();
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let transfers_add = sum_surplus_transfers(&entry, &value_fraction, &surplus, is_weighted, &surplus_fraction, &surplus_denom, state, opts);
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candidate_transfers.insert(candidate, transfers_orig + transfers_add);
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// Transfer candidate votes
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let parcel = Parcel {
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votes: entry.votes,
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value_fraction: reweight_value_fraction(&value_fraction, &surplus, is_weighted, &surplus_fraction, &surplus_denom, opts.round_surplus_fractions),
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source_order: state.num_elected + state.num_excluded,
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};
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let count_card = state.candidates.get_mut(candidate).unwrap();
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count_card.ballot_transfers += parcel.num_ballots();
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count_card.parcels.push(parcel);
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}
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// Record exhausted votes
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if opts.transferable_only {
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if transferable_votes > surplus {
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// No ballots exhaust
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} else {
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exhausted_transfers += &surplus - &transferable_votes;
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}
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} else {
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exhausted_transfers += sum_surplus_transfers(&result.exhausted, &value_fraction, &surplus, is_weighted, &surplus_fraction, &surplus_denom, state, opts);
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}
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// Transfer exhausted votes
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let parcel = Parcel {
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votes: result.exhausted.votes,
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value_fraction: value_fraction, // TODO: Reweight exhausted votes
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source_order: state.num_elected + state.num_excluded,
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};
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state.exhausted.ballot_transfers += parcel.num_ballots();
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state.exhausted.parcels.push(parcel);
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}
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let mut checksum = N::new();
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// Credit transferred votes
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// ballot_transfers updated above
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for (candidate, mut votes) in candidate_transfers {
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if let Some(dps) = opts.round_votes {
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votes.floor_mut(dps);
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}
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let count_card = state.candidates.get_mut(candidate).unwrap();
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count_card.transfer(&votes);
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checksum += votes;
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}
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// Credit exhausted votes
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if let Some(dps) = opts.round_votes {
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exhausted_transfers.floor_mut(dps);
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}
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state.exhausted.transfer(&exhausted_transfers);
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checksum += exhausted_transfers;
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// Finalise candidate votes
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let count_card = state.candidates.get_mut(elected_candidate).unwrap();
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count_card.transfers = -&surplus;
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count_card.votes.assign(state.quota.as_ref().unwrap());
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checksum -= surplus;
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count_card.finalised = true; // Mark surpluses as done
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// Update loss by fraction
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state.loss_fraction.transfer(&-checksum);
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}
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/// Perform one stage of a candidate exclusion according to the Gregory method, based on [STVOptions::exclusion]
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pub fn exclude_candidates<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions, excluded_candidates: Vec<&'a Candidate>)
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where
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for<'r> &'r N: ops::Mul<&'r N, Output=N>,
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for<'r> &'r N: ops::Div<&'r N, Output=N>,
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{
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// Used to give bulk excluded candidate the same order_elected
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let order_excluded = state.num_excluded + 1;
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for excluded_candidate in excluded_candidates.iter() {
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let count_card = state.candidates.get_mut(excluded_candidate).unwrap();
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|
|
|
// Rust borrow checker is unhappy if we try to put this in exclude_hopefuls ??!
|
|
if count_card.state != CandidateState::Excluded {
|
|
count_card.state = CandidateState::Excluded;
|
|
state.num_excluded += 1;
|
|
count_card.order_elected = -(order_excluded as isize);
|
|
|
|
constraints::update_constraints(state, opts);
|
|
}
|
|
}
|
|
|
|
// Determine votes to transfer in this stage
|
|
let mut parcels = Vec::new();
|
|
let mut votes_remain;
|
|
let mut checksum = N::new();
|
|
|
|
match opts.exclusion {
|
|
ExclusionMethod::SingleStage => {
|
|
// Exclude in one round
|
|
for excluded_candidate in excluded_candidates.iter() {
|
|
let count_card = state.candidates.get_mut(excluded_candidate).unwrap();
|
|
count_card.ballot_transfers = -count_card.num_ballots();
|
|
count_card.finalised = true;
|
|
|
|
parcels.append(&mut count_card.parcels);
|
|
|
|
// Update votes
|
|
checksum -= &count_card.votes;
|
|
count_card.transfers = -count_card.votes.clone();
|
|
count_card.votes = N::new();
|
|
}
|
|
votes_remain = false;
|
|
}
|
|
ExclusionMethod::ByValue => {
|
|
// Exclude by value
|
|
let excluded_with_votes: Vec<&&Candidate> = excluded_candidates.iter().filter(|c| !state.candidates[*c].finalised).collect();
|
|
|
|
if excluded_with_votes.is_empty() {
|
|
votes_remain = false;
|
|
} else {
|
|
// If candidates to exclude still having votes, select only those with the greatest value
|
|
let max_value = excluded_with_votes.iter()
|
|
.map(|c| state.candidates[*c].parcels.iter()
|
|
.map(|p| &p.value_fraction)
|
|
.max().unwrap())
|
|
.max().unwrap()
|
|
.clone();
|
|
|
|
votes_remain = false;
|
|
|
|
let mut votes = Vec::new();
|
|
|
|
for excluded_candidate in excluded_with_votes.iter() {
|
|
let count_card = state.candidates.get_mut(*excluded_candidate).unwrap();
|
|
let mut cc_parcels = Vec::new();
|
|
cc_parcels.append(&mut count_card.parcels);
|
|
|
|
// Filter out just those votes with max_value
|
|
let mut remaining_parcels = Vec::new();
|
|
|
|
for mut parcel in cc_parcels {
|
|
if parcel.value_fraction == max_value {
|
|
count_card.ballot_transfers -= parcel.num_ballots();
|
|
|
|
let votes_transferred = parcel.num_votes();
|
|
votes.append(&mut parcel.votes);
|
|
|
|
// Update votes
|
|
checksum -= &votes_transferred;
|
|
count_card.transfer(&-votes_transferred);
|
|
} else {
|
|
remaining_parcels.push(parcel);
|
|
}
|
|
}
|
|
|
|
if !remaining_parcels.is_empty() {
|
|
votes_remain = true;
|
|
}
|
|
|
|
// Leave remaining votes with candidate
|
|
count_card.parcels = remaining_parcels;
|
|
}
|
|
|
|
// Group all votes of one value in single parcel
|
|
parcels.push(Parcel {
|
|
votes: votes,
|
|
value_fraction: max_value,
|
|
source_order: 0, // source_order is unused in this mode
|
|
});
|
|
}
|
|
}
|
|
ExclusionMethod::BySource => {
|
|
// Exclude by source candidate
|
|
let excluded_with_votes: Vec<&&Candidate> = excluded_candidates.iter().filter(|c| !state.candidates[*c].finalised).collect();
|
|
|
|
if excluded_with_votes.is_empty() {
|
|
votes_remain = false;
|
|
} else {
|
|
// If candidates to exclude still having votes, select only those from the earliest elected/excluded source candidate
|
|
let min_order = excluded_with_votes.iter()
|
|
.map(|c| state.candidates[*c].parcels.iter()
|
|
.map(|p| p.source_order)
|
|
.min().unwrap())
|
|
.min().unwrap();
|
|
|
|
votes_remain = false;
|
|
|
|
for excluded_candidate in excluded_with_votes.iter() {
|
|
let count_card = state.candidates.get_mut(*excluded_candidate).unwrap();
|
|
let mut cc_parcels = Vec::new();
|
|
cc_parcels.append(&mut count_card.parcels);
|
|
|
|
// Filter out just those votes with min_order
|
|
let mut remaining_parcels = Vec::new();
|
|
|
|
for parcel in cc_parcels {
|
|
if parcel.source_order == min_order {
|
|
count_card.ballot_transfers -= parcel.num_ballots();
|
|
|
|
let votes_transferred = parcel.num_votes();
|
|
parcels.push(parcel);
|
|
|
|
// Update votes
|
|
checksum -= &votes_transferred;
|
|
count_card.transfer(&-votes_transferred);
|
|
} else {
|
|
remaining_parcels.push(parcel);
|
|
}
|
|
}
|
|
|
|
if !remaining_parcels.is_empty() {
|
|
votes_remain = true;
|
|
}
|
|
|
|
// Leave remaining votes with candidate
|
|
count_card.parcels = remaining_parcels;
|
|
}
|
|
}
|
|
}
|
|
ExclusionMethod::ParcelsByOrder => {
|
|
// Exclude by parcel by order
|
|
if excluded_candidates.len() > 1 && excluded_candidates.iter().any(|c| !state.candidates[c].parcels.is_empty()) {
|
|
// TODO: We can probably support this actually
|
|
panic!("--exclusion parcels_by_order is incompatible with multiple exclusions");
|
|
}
|
|
|
|
let count_card = state.candidates.get_mut(excluded_candidates[0]).unwrap();
|
|
|
|
if count_card.parcels.is_empty() {
|
|
votes_remain = false;
|
|
} else {
|
|
parcels.push(count_card.parcels.remove(0));
|
|
votes_remain = !count_card.parcels.is_empty();
|
|
|
|
count_card.ballot_transfers -= parcels.first().unwrap().num_ballots();
|
|
|
|
// Update votes
|
|
let votes_transferred = parcels.first().unwrap().num_votes();
|
|
checksum -= &votes_transferred;
|
|
count_card.transfer(&-votes_transferred);
|
|
}
|
|
}
|
|
_ => panic!()
|
|
}
|
|
|
|
let mut total_ballots = N::new();
|
|
let mut total_votes = N::new();
|
|
|
|
let value = match parcels.first() { Some(p) => Some(p.value_fraction.clone()), _ => None };
|
|
|
|
let mut candidate_transfers: HashMap<&Candidate, N> = HashMap::new();
|
|
for candidate in state.election.candidates.iter() {
|
|
candidate_transfers.insert(candidate, N::new());
|
|
}
|
|
let mut exhausted_transfers = N::new();
|
|
|
|
for parcel in parcels {
|
|
// Count next preferences
|
|
let result = super::next_preferences(state, parcel.votes);
|
|
|
|
total_ballots += &result.total_ballots;
|
|
total_votes += &result.total_ballots * &parcel.value_fraction;
|
|
|
|
// Transfer candidate votes
|
|
for (candidate, entry) in result.candidates.into_iter() {
|
|
let parcel = Parcel {
|
|
votes: entry.votes,
|
|
value_fraction: parcel.value_fraction.clone(),
|
|
source_order: state.num_elected + state.num_excluded,
|
|
};
|
|
|
|
// Record transfers
|
|
let transfers_orig = candidate_transfers.remove(candidate).unwrap();
|
|
candidate_transfers.insert(candidate, transfers_orig + &entry.num_ballots * &parcel.value_fraction);
|
|
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.ballot_transfers += parcel.num_ballots();
|
|
count_card.parcels.push(parcel);
|
|
}
|
|
|
|
// Transfer exhausted votes
|
|
let parcel = Parcel {
|
|
votes: result.exhausted.votes,
|
|
value_fraction: parcel.value_fraction,
|
|
source_order: state.num_elected + state.num_excluded,
|
|
};
|
|
|
|
// Record transfers
|
|
state.exhausted.ballot_transfers += parcel.num_ballots();
|
|
exhausted_transfers += &result.exhausted.num_ballots * &parcel.value_fraction;
|
|
state.exhausted.parcels.push(parcel);
|
|
|
|
// TODO: Detailed transfers logs
|
|
}
|
|
|
|
if let ExclusionMethod::SingleStage = opts.exclusion {
|
|
if total_ballots == N::one() {
|
|
state.logger.log_literal(format!("Transferring 1 ballot, totalling {:.dps$} votes.", total_votes, dps=opts.pp_decimals));
|
|
} else {
|
|
state.logger.log_literal(format!("Transferring {:.0} ballots, totalling {:.dps$} votes.", total_ballots, total_votes, dps=opts.pp_decimals));
|
|
}
|
|
} else {
|
|
if total_ballots.is_zero() {
|
|
state.logger.log_literal(format!("Transferring 0 ballots, totalling {:.dps$} votes.", 0, dps=opts.pp_decimals));
|
|
} else if total_ballots == N::one() {
|
|
state.logger.log_literal(format!("Transferring 1 ballot, totalling {:.dps$} votes, received at value {:.dps2$}.", total_votes, value.unwrap(), dps=opts.pp_decimals, dps2=max(opts.pp_decimals, 2)));
|
|
} else {
|
|
state.logger.log_literal(format!("Transferring {:.0} ballots, totalling {:.dps$} votes, received at value {:.dps2$}.", total_ballots, total_votes, value.unwrap(), dps=opts.pp_decimals, dps2=max(opts.pp_decimals, 2)));
|
|
}
|
|
}
|
|
|
|
// Credit transferred votes
|
|
// ballot_transfers updated above
|
|
for (candidate, mut votes) in candidate_transfers {
|
|
if let Some(dps) = opts.round_votes {
|
|
votes.floor_mut(dps);
|
|
}
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.transfer(&votes);
|
|
checksum += votes;
|
|
}
|
|
|
|
// Credit exhausted votes
|
|
if let Some(dps) = opts.round_votes {
|
|
exhausted_transfers.floor_mut(dps);
|
|
}
|
|
state.exhausted.transfer(&exhausted_transfers);
|
|
checksum += exhausted_transfers;
|
|
|
|
if !votes_remain {
|
|
// Finalise candidate votes
|
|
for excluded_candidate in excluded_candidates.into_iter() {
|
|
let count_card = state.candidates.get_mut(excluded_candidate).unwrap();
|
|
checksum -= &count_card.votes;
|
|
count_card.transfers -= &count_card.votes;
|
|
count_card.votes = N::new();
|
|
count_card.finalised = true;
|
|
}
|
|
|
|
if opts.exclusion != ExclusionMethod::SingleStage {
|
|
state.logger.log_literal("Exclusion complete.".to_string());
|
|
}
|
|
}
|
|
|
|
// Update loss by fraction
|
|
state.loss_fraction.transfer(&-checksum);
|
|
}
|
|
|
|
/// Perform one stage of a candidate exclusion according to the Wright method
|
|
pub fn wright_exclude_candidates<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions, excluded_candidates: Vec<&'a Candidate>)
|
|
where
|
|
for<'r> &'r N: ops::Sub<&'r N, Output=N>,
|
|
for<'r> &'r N: ops::Mul<&'r N, Output=N>,
|
|
for<'r> &'r N: ops::Div<&'r N, Output=N>,
|
|
{
|
|
// Used to give bulk excluded candidate the same order_elected
|
|
let order_excluded = state.num_excluded + 1;
|
|
|
|
for excluded_candidate in excluded_candidates.iter() {
|
|
let count_card = state.candidates.get_mut(excluded_candidate).unwrap();
|
|
|
|
// Rust borrow checker is unhappy if we try to put this in exclude_hopefuls ??!
|
|
if count_card.state != CandidateState::Excluded {
|
|
count_card.state = CandidateState::Excluded;
|
|
state.num_excluded += 1;
|
|
count_card.order_elected = -(order_excluded as isize);
|
|
}
|
|
|
|
constraints::update_constraints(state, opts);
|
|
}
|
|
|
|
// Reset count
|
|
for (_, count_card) in state.candidates.iter_mut() {
|
|
if count_card.order_elected > 0 {
|
|
count_card.order_elected = 0;
|
|
}
|
|
count_card.parcels.clear();
|
|
count_card.votes = N::new();
|
|
count_card.transfers = N::new();
|
|
count_card.state = match count_card.state {
|
|
CandidateState::Withdrawn => CandidateState::Withdrawn,
|
|
CandidateState::Excluded => CandidateState::Excluded,
|
|
_ => CandidateState::Hopeful,
|
|
};
|
|
|
|
if count_card.state == CandidateState::Excluded {
|
|
count_card.finalised = true;
|
|
} else {
|
|
count_card.finalised = false;
|
|
}
|
|
}
|
|
|
|
state.exhausted.votes = N::new();
|
|
state.exhausted.transfers = N::new();
|
|
state.loss_fraction.votes = N::new();
|
|
state.loss_fraction.transfers = N::new();
|
|
|
|
state.num_elected = 0;
|
|
|
|
let orig_title = state.title.clone();
|
|
|
|
// Redistribute first preferences
|
|
super::distribute_first_preferences(state, opts);
|
|
|
|
state.kind = Some("Exclusion of");
|
|
state.title = orig_title;
|
|
|
|
// Trigger recalculation of quota within stv::count_one_stage
|
|
state.quota = None;
|
|
state.vote_required_election = None;
|
|
}
|