1276 lines
43 KiB
Rust
1276 lines
43 KiB
Rust
/* OpenTally: Open-source election vote counting
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* Copyright © 2021–2023 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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/// Gregory methods of surplus distributions
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pub mod gregory;
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/// Meek method of surplus distributions, etc.
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pub mod meek;
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/// Helper functions for HTML reporting output
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pub mod html;
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/// Random sample methods of surplus distributions
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pub mod sample;
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/// WebAssembly wrappers
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//#[cfg(target_arch = "wasm32")]
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pub mod wasm;
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mod options;
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pub use options::*;
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use crate::candmap::CandidateMap;
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use crate::constraints;
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use crate::election::{Candidate, CandidateState, CountCard, CountState, Election, RollbackState, StageKind, Vote};
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use crate::numbers::Number;
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use crate::sharandom::SHARandom;
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use crate::ties::{self, TieStrategy};
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use itertools::Itertools;
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use std::fmt;
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use std::ops;
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/// An error during the STV count
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#[derive(Debug, Eq, PartialEq)]
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pub enum STVError {
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/// Options for the count are invalid
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InvalidOptions(&'static str),
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/// Tie could not be resolved
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UnresolvedTie,
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/// Unrecoverable error during the count
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CannotCompleteCount(&'static str),
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}
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impl STVError {
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/// Describe the error
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pub fn describe(&self) -> &'static str {
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match self {
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STVError::InvalidOptions(s) => s,
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STVError::UnresolvedTie => "Unable to resolve tie",
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STVError::CannotCompleteCount(s) => s,
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}
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}
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}
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impl fmt::Display for STVError {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.write_str(self.describe())?;
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return Ok(());
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}
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}
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/// Preprocess the given election
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pub fn preprocess_election<N: Number>(election: &mut Election<N>, opts: &STVOptions) {
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// Normalise ballots if required
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if opts.surplus == SurplusMethod::IHare || opts.surplus == SurplusMethod::Hare {
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election.normalise_ballots();
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}
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// Process equal rankings
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election.realise_equal_rankings();
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}
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/// Distribute first preferences, and initialise other states such as the random number generator and tie-breaking rules
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pub fn count_init<'a, N: Number>(state: &mut CountState<'a, N>, opts: &'a STVOptions) -> Result<(), STVError>
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where
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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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{
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// Initialise RNG
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for t in opts.ties.iter() {
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if let TieStrategy::Random(seed) = t {
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state.random = Some(SHARandom::new(seed));
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}
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}
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constraints::update_constraints(state, opts);
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distribute_first_preferences(state, opts);
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calculate_quota(state, opts);
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elect_hopefuls(state, opts, true)?;
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init_tiebreaks(state, opts);
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return Ok(());
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}
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/// Perform a single stage of the STV count
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///
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/// Returns `true` if the count is complete, otherwise `false`.
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pub fn count_one_stage<'a, N: Number>(state: &mut CountState<'a, 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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state.transfer_table = None;
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state.logger.entries.clear();
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state.step_all();
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// Finish count
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if finished_before_stage(state) {
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return Ok(true);
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}
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if let RollbackState::Normal = state.rollback_state {
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} else {
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constraints::rollback_one_stage(state, opts)?;
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elect_hopefuls(state, opts, true)?;
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update_tiebreaks(state, opts);
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return Ok(false);
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}
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// Attempt early bulk election
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if opts.early_bulk_elect {
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if bulk_elect(state, opts)? {
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return Ok(false);
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}
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}
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// Continue exclusions
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if continue_exclusion(state, opts)? {
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calculate_quota(state, opts);
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elect_hopefuls(state, opts, true)?;
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update_tiebreaks(state, opts);
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return Ok(false);
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}
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// Exclude doomed candidates
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if exclude_doomed(state, opts)? {
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calculate_quota(state, opts);
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elect_hopefuls(state, opts, true)?;
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update_tiebreaks(state, opts);
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return Ok(false);
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}
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// Distribute surpluses
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if distribute_surpluses(state, opts)? {
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calculate_quota(state, opts);
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elect_hopefuls(state, opts, true)?;
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update_tiebreaks(state, opts);
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return Ok(false);
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}
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// Attempt late bulk election
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if bulk_elect(state, opts)? {
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return Ok(false);
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}
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// Sanity check
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let num_hopefuls = state.candidates.values()
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.filter(|cc| cc.state == CandidateState::Hopeful)
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.count();
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if num_hopefuls == 0 {
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return Err(STVError::CannotCompleteCount("Insufficient continuing candidates to complete count"));
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}
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// Exclude lowest hopeful
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exclude_hopefuls(state, opts)?; // Cannot fail
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calculate_quota(state, opts);
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elect_hopefuls(state, opts, true)?;
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update_tiebreaks(state, opts);
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return Ok(false);
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}
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/// See [next_preferences]
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pub struct NextPreferencesResult<'a, N> {
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/// [NextPreferencesEntry] for each [Candidate]
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pub candidates: CandidateMap<'a, NextPreferencesEntry<'a, N>>,
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/// [NextPreferencesEntry] for exhausted ballots
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pub exhausted: NextPreferencesEntry<'a, N>,
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/// Total weight of ballots examined
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pub total_ballots: N,
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}
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/// See [next_preferences]
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pub struct NextPreferencesEntry<'a, N> {
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/// Votes recording a next preference for the candidate
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pub votes: Vec<Vote<'a, N>>,
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/// Weight of such ballots
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pub num_ballots: N,
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}
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/// Count the given votes, grouping according to next available preference
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pub fn next_preferences<'a, N: Number>(state: &CountState<'a, N>, votes: Vec<Vote<'a, N>>) -> NextPreferencesResult<'a, N> {
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let mut result = NextPreferencesResult {
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candidates: CandidateMap::with_capacity(state.election.candidates.len()),
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exhausted: NextPreferencesEntry {
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votes: Vec::new(),
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num_ballots: N::new(),
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},
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total_ballots: N::new(),
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};
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for mut vote in votes.into_iter() {
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result.total_ballots += &vote.ballot.orig_value;
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let mut next_candidate = None;
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while let Some(preference) = vote.next_preference() {
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let candidate = &state.election.candidates[preference];
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let count_card = &state.candidates[candidate];
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if let CandidateState::Hopeful | CandidateState::Guarded = count_card.state {
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next_candidate = Some(candidate);
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break;
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}
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}
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// Have to structure like this to satisfy Rust's borrow checker
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if let Some(candidate) = next_candidate {
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match result.candidates.get_mut(candidate) {
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Some(entry) => {
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entry.num_ballots += &vote.ballot.orig_value;
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entry.votes.push(vote);
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}
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None => {
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let entry = NextPreferencesEntry {
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num_ballots: vote.ballot.orig_value.clone(),
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votes: vec![vote],
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};
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result.candidates.insert(candidate, entry);
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}
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}
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} else {
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result.exhausted.num_ballots += &vote.ballot.orig_value;
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result.exhausted.votes.push(vote);
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}
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}
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return result;
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}
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/// Distribute first preference votes
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fn distribute_first_preferences<N: Number>(state: &mut CountState<N>, opts: &STVOptions)
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where
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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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{
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match opts.surplus {
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SurplusMethod::WIG | SurplusMethod::UIG | SurplusMethod::EG | SurplusMethod::IHare | SurplusMethod::Hare => {
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gregory::distribute_first_preferences(state, opts);
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}
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SurplusMethod::Meek => {
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meek::distribute_first_preferences(state, opts);
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}
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}
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}
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/// Calculate the quota, given the total vote, according to [STVOptions::quota]
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fn total_to_quota<N: Number>(mut total: N, seats: usize, opts: &STVOptions) -> N {
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match opts.quota {
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QuotaType::Droop | QuotaType::DroopExact => {
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total /= N::from(seats + 1);
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}
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QuotaType::Hare | QuotaType::HareExact => {
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total /= N::from(seats);
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}
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}
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if let Some(dps) = opts.round_quota {
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match opts.quota {
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QuotaType::Droop | QuotaType::Hare => {
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// Increment to next available increment
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let mut factor = N::from(10);
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factor.pow_assign(dps as i32);
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total *= &factor;
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total.floor_mut(0);
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total += N::one();
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total /= factor;
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}
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QuotaType::DroopExact | QuotaType::HareExact => {
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// Round up to next available increment if necessary
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total.ceil_mut(dps);
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}
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}
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}
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return total;
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}
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/// Update vote required for election according to ERS97/ERS76 rules
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fn update_vre_ers<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
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if opts.quota_mode == QuotaMode::ERS76 && state.num_excluded == 0 && (state.num_elected == 0 || state.candidates.values().all(|cc| !cc.finalised)) {
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// ERS76 rules: Do not update VRE until a surplus is distributed or candidate is excluded
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state.vote_required_election = state.quota.clone();
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return;
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}
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let mut log = String::new();
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// Calculate active vote
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let active_vote = state.active_vote();
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log.push_str(format!("Active vote is {:.dps$}, so the vote required for election is ", active_vote, dps=opts.pp_decimals).as_str());
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let vote_req = active_vote / N::from(state.election.seats - state.num_elected + 1);
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if &vote_req < state.quota.as_ref().unwrap() {
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// VRE is less than the quota
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if let Some(v) = &state.vote_required_election {
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if &vote_req != v {
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log.push_str(format!("{:.dps$}.", vote_req, dps=opts.pp_decimals).as_str());
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state.vote_required_election = Some(vote_req);
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state.logger.log_literal(log);
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}
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} else {
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log.push_str(format!("{:.dps$}.", vote_req, dps=opts.pp_decimals).as_str());
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state.vote_required_election = Some(vote_req);
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state.logger.log_literal(log);
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}
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} else {
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// VRE is not less than the quota, so use the quota
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state.vote_required_election = state.quota.clone();
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}
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}
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/// Update vote required for election if only one candidate remains, used in early bulk election
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///
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/// Assumes early bulk election is enabled.
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fn update_vre_bulk<N: Number>(state: &mut CountState<N>, _opts: &STVOptions) {
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// If --early-bulk-elect and one candidate remains, VRE is half of the active vote
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// For display purposes only
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if state.election.seats - state.num_elected == 1 {
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//let mut log = String::new();
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// Calculate active vote
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let active_vote = state.active_vote();
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//log.push_str(format!("Active vote is {:.dps$}, so the vote required for election is ", active_vote, dps=opts.pp_decimals).as_str());
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let vote_req = active_vote / N::from(state.election.seats - state.num_elected + 1);
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if &vote_req < state.quota.as_ref().unwrap() {
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// VRE is less than the quota
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//if let Some(v) = &state.vote_required_election {
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// if &vote_req != v {
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//log.push_str(format!("{:.dps$}.", vote_req, dps=opts.pp_decimals).as_str());
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state.vote_required_election = Some(vote_req);
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//state.logger.log_literal(log);
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// }
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//} else {
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//log.push_str(format!("{:.dps$}.", vote_req, dps=opts.pp_decimals).as_str());
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// state.vote_required_election = Some(vote_req);
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//state.logger.log_literal(log);
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//}
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}
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}
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}
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/// Calculate the quota according to [STVOptions::quota]
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fn calculate_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
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if state.quota.is_none() || opts.quota_mode == QuotaMode::DynamicByTotal {
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// Calculate quota by total vote
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let mut log = String::new();
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// Calculate the total vote
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let total_vote = state.total_vote();
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if state.election.seats == 1 {
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log.push_str(format!("{:.dps$} usable votes, so a majority is ", total_vote, dps=opts.pp_decimals).as_str());
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} else {
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log.push_str(format!("{:.dps$} usable votes, so the quota is ", total_vote, dps=opts.pp_decimals).as_str());
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}
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let quota = total_to_quota(total_vote, state.election.seats, opts);
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log.push_str(format!("{:.dps$}.", quota, dps=opts.pp_decimals).as_str());
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state.quota = Some(quota);
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state.logger.log_literal(log);
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} else if opts.quota_mode == QuotaMode::DynamicByActive {
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// Calculate quota by active vote
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let mut log = String::new();
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// Calculate the active vote
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let active_vote = state.active_vote();
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if state.election.seats == 1 {
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log.push_str(format!("Active vote is {:.dps$}, so a majority is ", active_vote, dps=opts.pp_decimals).as_str());
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} else {
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log.push_str(format!("Active vote is {:.dps$}, so the quota is ", active_vote, dps=opts.pp_decimals).as_str());
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}
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// TODO: Calculate according to --quota ?
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let quota = active_vote / N::from(state.election.seats - state.num_elected + 1);
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log.push_str(format!("{:.dps$}.", quota, dps=opts.pp_decimals).as_str());
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state.quota = Some(quota);
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state.logger.log_literal(log);
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}
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if opts.quota_mode == QuotaMode::ERS97 || opts.quota_mode == QuotaMode::ERS76 {
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// ERS97/ERS76 rules
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// -------------------------
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// (ERS97) Reduce quota if allowable
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if opts.quota_mode == QuotaMode::ERS97 && state.num_elected == 0 {
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let mut log = String::new();
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// Calculate the total vote
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let total_vote = state.total_vote();
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if state.election.seats == 1 {
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log.push_str(format!("{:.dps$} usable votes, so a majority is ", total_vote, dps=opts.pp_decimals).as_str());
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} else {
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log.push_str(format!("{:.dps$} usable votes, so the quota is reduced to ", total_vote, dps=opts.pp_decimals).as_str());
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}
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let quota = total_to_quota(total_vote, state.election.seats, opts);
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if "a < state.quota.as_ref().unwrap() {
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log.push_str(format!("{:.dps$}.", quota, dps=opts.pp_decimals).as_str());
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state.quota = Some(quota);
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state.logger.log_literal(log);
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}
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}
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// ------------------------------------
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// Calculate vote required for election
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if state.num_elected < state.election.seats {
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update_vre_ers(state, opts);
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}
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} else {
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// No ERS97/ERS76 rules
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if opts.early_bulk_elect {
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update_vre_bulk(state, opts);
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}
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}
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}
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/// Compare the candidate's votes with the specified target according to [STVOptions::quota_criterion]
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fn cmp_quota_criterion<N: Number>(quota: &N, count_card: &CountCard<N>, opts: &STVOptions) -> bool {
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match opts.quota_criterion {
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QuotaCriterion::GreaterOrEqual => {
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return count_card.votes >= *quota;
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}
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QuotaCriterion::Greater => {
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return count_card.votes > *quota;
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}
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}
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}
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/// Determine if the given candidate meets the vote required to be elected, according to [STVOptions::quota_criterion] and [STVOptions::quota_mode]
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fn meets_vre<N: Number>(state: &CountState<N>, count_card: &CountCard<N>, opts: &STVOptions) -> bool {
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if opts.quota_mode == QuotaMode::ERS97 || opts.quota_mode == QuotaMode::ERS76 {
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// VRE is set because ERS97/ERS76 rules
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return cmp_quota_criterion(state.vote_required_election.as_ref().unwrap(), count_card, opts);
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} else {
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// VRE is set (if at all) for display purposes only so ignore it here
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return cmp_quota_criterion(state.quota.as_ref().unwrap(), count_card, opts);
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}
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}
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/// Declare elected the continuing candidates leading for remaining vacancies if they cannot be overtaken
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///
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/// Returns `true` if any candidates were elected.
|
|
fn elect_sure_winners<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<bool, STVError> {
|
|
// Do not interrupt rolling back!!
|
|
if let RollbackState::Normal = state.rollback_state {
|
|
} else {
|
|
return Ok(false);
|
|
}
|
|
|
|
if state.num_elected >= state.election.seats {
|
|
return Ok(false);
|
|
}
|
|
|
|
let num_vacancies = state.election.seats - state.num_elected;
|
|
|
|
let mut hopefuls: Vec<(&Candidate, &CountCard<N>)> = state.election.candidates.iter()
|
|
.map(|c| (c, &state.candidates[c]))
|
|
.filter(|(_, cc)| cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded)
|
|
.collect();
|
|
|
|
hopefuls.sort_unstable_by(|a, b| b.1.votes.cmp(&a.1.votes));
|
|
|
|
let mut total_trailing = N::new();
|
|
// For leading candidates, count only untransferred surpluses
|
|
total_trailing += state.total_surplus_of(hopefuls.iter().take(num_vacancies).map(|(_, cc)| *cc));
|
|
// For trailing candidates, count all votes
|
|
total_trailing += state.total_votes_of(hopefuls.iter().skip(num_vacancies).map(|(_, cc)| *cc));
|
|
// Add finally any votes awaiting transfer
|
|
total_trailing += state.candidates.values().fold(N::new(), |mut acc, cc| {
|
|
match cc.state {
|
|
CandidateState::Elected => {
|
|
if !cc.finalised && &cc.votes > state.quota.as_ref().unwrap() {
|
|
acc += &cc.votes;
|
|
acc -= state.quota.as_ref().unwrap();
|
|
}
|
|
}
|
|
CandidateState::Hopeful | CandidateState::Guarded | CandidateState::Withdrawn => {}
|
|
CandidateState::Excluded | CandidateState::Doomed => {
|
|
acc += &cc.votes;
|
|
}
|
|
}
|
|
acc
|
|
});
|
|
|
|
if num_vacancies - 1 < hopefuls.len() {
|
|
let last_winner = hopefuls[num_vacancies - 1].1;
|
|
if last_winner.votes <= total_trailing {
|
|
return Ok(false);
|
|
}
|
|
}
|
|
|
|
let mut leading_hopefuls: Vec<&Candidate> = hopefuls.iter().take(num_vacancies).map(|(c, _)| *c).collect();
|
|
|
|
match constraints::test_constraints_any_time(state, &leading_hopefuls, CandidateState::Elected) {
|
|
Ok(_) => {}
|
|
Err(_) => { return Ok(false); } // Bulk election conflicts with constraints
|
|
}
|
|
|
|
// Bulk election is possible!
|
|
// Elect all leading candidates
|
|
|
|
if num_vacancies > 1 {
|
|
// Update VRE
|
|
// (If num_vacancies == 1, this has already been done in calculate_quota)
|
|
state.vote_required_election = Some(total_trailing);
|
|
}
|
|
|
|
while !leading_hopefuls.is_empty() && state.num_elected < state.election.seats {
|
|
let max_cands = ties::multiple_max_by(&leading_hopefuls, |c| &state.candidates[c].votes);
|
|
let candidate = if max_cands.len() > 1 {
|
|
choose_highest(state, opts, &max_cands, "Which candidate to elect?")?
|
|
} else {
|
|
max_cands[0]
|
|
};
|
|
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.state = CandidateState::Elected;
|
|
state.num_elected += 1;
|
|
count_card.order_elected = state.num_elected as isize;
|
|
|
|
state.logger.log_smart(
|
|
"As they cannot now be overtaken, {} is elected to fill the remaining vacancy.",
|
|
"As they cannot now be overtaken, {} are elected to fill the remaining vacancies.",
|
|
vec![candidate.name.as_str()] // rust-analyzer doesn't understand &String -> &str
|
|
);
|
|
|
|
leading_hopefuls.remove(leading_hopefuls.iter().position(|c| *c == candidate).unwrap());
|
|
}
|
|
|
|
constraints::update_constraints(state, opts);
|
|
|
|
return Ok(true);
|
|
}
|
|
|
|
/// Declare elected all candidates meeting the quota, and (if enabled) any candidates who can be early bulk elected because they have sufficiently many votes
|
|
///
|
|
/// Returns `true` if any candidates were elected.
|
|
fn elect_hopefuls<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions, if_immediate: bool) -> Result<bool, STVError> {
|
|
if opts.immediate_elect != if_immediate && opts.surplus != SurplusMethod::Meek {
|
|
// For --no-immediate-elect
|
|
return Ok(false);
|
|
}
|
|
|
|
let mut cands_meeting_quota: Vec<(&Candidate, &CountCard<N>)> = state.election.candidates.iter() // Present in order in case of tie
|
|
.map(|c| (c, &state.candidates[c]))
|
|
.filter(|(_, cc)| { (cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded) && meets_vre(state, cc, opts) })
|
|
.collect();
|
|
|
|
// Sort by votes
|
|
cands_meeting_quota.sort_unstable_by(|a, b| b.1.votes.cmp(&a.1.votes));
|
|
let mut cands_meeting_quota: Vec<&Candidate> = cands_meeting_quota.iter().map(|(c, _)| *c).collect();
|
|
|
|
let elected = !cands_meeting_quota.is_empty();
|
|
|
|
while !cands_meeting_quota.is_empty() && state.num_elected < state.election.seats {
|
|
// Declare elected in descending order of votes
|
|
let max_cands = ties::multiple_max_by(&cands_meeting_quota, |c| &state.candidates[c].votes);
|
|
let candidate = if max_cands.len() > 1 {
|
|
choose_highest(state, opts, &max_cands, "Which candidate to elect?")?
|
|
} else {
|
|
max_cands[0]
|
|
};
|
|
|
|
if opts.constraint_mode == ConstraintMode::RepeatCount && state.election.constraints.is_some() {
|
|
if let Err((constraint, group)) = constraints::test_constraints_immediate(state, &[candidate], CandidateState::Elected) {
|
|
// This election would violate a constraint, so stop here
|
|
state.logger.log_smart(
|
|
"The election of {} now would violate constraints.",
|
|
"The election of {} now would violate constraints.",
|
|
vec![candidate.name.as_str()]
|
|
);
|
|
|
|
// Trigger rollback
|
|
constraints::init_repeat_count_rollback(state, constraint, group);
|
|
|
|
return Ok(elected);
|
|
}
|
|
}
|
|
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.state = CandidateState::Elected;
|
|
state.num_elected += 1;
|
|
count_card.order_elected = state.num_elected as isize;
|
|
|
|
let elected_on_quota;
|
|
if cmp_quota_criterion(state.quota.as_ref().unwrap(), count_card, opts) {
|
|
// Elected with a quota
|
|
elected_on_quota = true;
|
|
if state.election.seats == 1 {
|
|
state.logger.log_smart(
|
|
"{} reaches a majority and is elected.",
|
|
"{} reach a majority and are elected.", // This one is impossible
|
|
vec![candidate.name.as_str()]
|
|
);
|
|
} else {
|
|
state.logger.log_smart(
|
|
"{} meets the quota and is elected.",
|
|
"{} meet the quota and are elected.",
|
|
vec![candidate.name.as_str()]
|
|
);
|
|
}
|
|
} else {
|
|
// Elected with vote required
|
|
elected_on_quota = false;
|
|
state.logger.log_smart(
|
|
"{} meets the vote required and is elected.",
|
|
"{} meet the vote required and are elected.",
|
|
vec![candidate.name.as_str()]
|
|
);
|
|
}
|
|
|
|
if constraints::update_constraints(state, opts) {
|
|
// Recheck as some candidates may have been doomed
|
|
let mut cmq: Vec<(&Candidate, &CountCard<N>)> = state.election.candidates.iter() // Present in order in case of tie
|
|
.map(|c| (c, &state.candidates[c]))
|
|
.filter(|(_, cc)| { (cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded) && meets_vre(state, cc, opts) })
|
|
.collect();
|
|
cmq.sort_unstable_by(|a, b| b.1.votes.cmp(&a.1.votes));
|
|
cands_meeting_quota = cmq.iter().map(|(c, _)| *c).collect();
|
|
} else {
|
|
cands_meeting_quota.remove(cands_meeting_quota.iter().position(|c| *c == candidate).unwrap());
|
|
}
|
|
|
|
if opts.quota_mode == QuotaMode::ERS97 || opts.quota_mode == QuotaMode::ERS76 || opts.quota_mode == QuotaMode::DynamicByActive {
|
|
// Vote required for election may have changed
|
|
// ERS97: Check this after every elected candidate (cf. model election)
|
|
// ERS76: Check this after every candidate elected on a quota, but all at once for candidates elected on VRE (cf. model election)
|
|
if opts.quota_mode == QuotaMode::ERS97 || (opts.quota_mode == QuotaMode::ERS76 && elected_on_quota) || opts.quota_mode == QuotaMode::DynamicByActive {
|
|
calculate_quota(state, opts);
|
|
|
|
// Repeat in case vote required for election has changed
|
|
match elect_hopefuls(state, opts, true) {
|
|
Ok(_) => { break; }
|
|
Err(e) => { return Err(e); }
|
|
}
|
|
}
|
|
} else if opts.early_bulk_elect {
|
|
// Vote required for election may have changed for display purposes
|
|
update_vre_bulk(state, opts);
|
|
}
|
|
}
|
|
|
|
// Determine if early bulk election can be effected
|
|
if opts.early_bulk_elect {
|
|
if elect_sure_winners(state, opts)? {
|
|
return Ok(true);
|
|
}
|
|
}
|
|
|
|
return Ok(elected);
|
|
}
|
|
|
|
/// Determine whether the transfer of all surpluses can be deferred
|
|
///
|
|
/// The value of [STVOptions::defer_surpluses] is not taken into account and must be handled by the caller.
|
|
fn can_defer_surpluses<N: Number>(state: &CountState<N>, opts: &STVOptions, total_surpluses: &N) -> bool
|
|
where
|
|
for<'r> &'r N: ops::Sub<&'r N, Output=N>
|
|
{
|
|
let mut hopefuls: Vec<(&Candidate, &CountCard<N>)> = state.candidates.iter()
|
|
.filter(|(_, cc)| cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded)
|
|
.collect();
|
|
hopefuls.sort_unstable_by(|(_, cc1), (_, cc2)| cc1.votes.cmp(&cc2.votes));
|
|
|
|
// Surpluses can always be deferred if there is only 1 continuing candidate
|
|
if hopefuls.len() <= 1 {
|
|
return true;
|
|
}
|
|
|
|
// Do not defer if this could affect a bulk exclusion
|
|
if opts.bulk_exclude {
|
|
let to_exclude = hopefuls_to_bulk_exclude(state, opts);
|
|
let num_to_exclude = to_exclude.len();
|
|
if num_to_exclude > 0 {
|
|
let total_excluded = state.total_votes_of(to_exclude.into_iter().map(|c| &state.candidates[c]));
|
|
if total_surpluses >= &(&hopefuls[num_to_exclude].1.votes - &total_excluded) {
|
|
return false;
|
|
} else {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Do not defer if this could change the last 2 candidates
|
|
if total_surpluses >= &(&hopefuls[1].1.votes - &hopefuls[0].1.votes) {
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// Distribute surpluses according to [STVOptions::surplus]
|
|
///
|
|
/// Returns `true` if any surpluses were distributed.
|
|
fn distribute_surpluses<N: Number>(state: &mut CountState<N>, opts: &STVOptions) -> Result<bool, STVError>
|
|
where
|
|
for<'r> &'r N: ops::Add<&'r N, Output=N>,
|
|
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>,
|
|
for<'r> &'r N: ops::Neg<Output=N>,
|
|
{
|
|
match opts.surplus {
|
|
SurplusMethod::WIG | SurplusMethod::UIG | SurplusMethod::EG | SurplusMethod::IHare | SurplusMethod::Hare => {
|
|
return gregory::distribute_surpluses(state, opts);
|
|
}
|
|
SurplusMethod::Meek => {
|
|
return meek::distribute_surpluses(state, opts);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Determine if, with the proposed exclusion of num_to_exclude candidates (if any), a bulk election can be made
|
|
fn can_bulk_elect<N: Number>(state: &CountState<N>, num_to_exclude: usize) -> bool {
|
|
let num_hopefuls = state.election.candidates.iter()
|
|
.filter(|c| {
|
|
let cc = &state.candidates[c];
|
|
// Include doomed candidates here as these are included in num_to_exclude and so will later be subtracted
|
|
return cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded || cc.state == CandidateState::Doomed;
|
|
})
|
|
.count();
|
|
|
|
if num_hopefuls - num_to_exclude > 0 && state.num_elected + num_hopefuls - num_to_exclude <= state.election.seats {
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Declare all continuing candidates to be elected
|
|
fn do_bulk_elect<N: Number>(state: &mut CountState<N>, opts: &STVOptions, template1: &'static str, template2: &'static str) -> Result<(), STVError> {
|
|
let mut hopefuls: Vec<&Candidate> = state.election.candidates.iter()
|
|
.filter(|c| {
|
|
let cc = &state.candidates[c];
|
|
return cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded;
|
|
})
|
|
.collect();
|
|
|
|
// Bulk elect all remaining candidates
|
|
while !hopefuls.is_empty() {
|
|
let max_cands = ties::multiple_max_by(&hopefuls, |c| &state.candidates[c].votes);
|
|
let candidate = if max_cands.len() > 1 {
|
|
choose_highest(state, opts, &max_cands, "Which candidate to elect?")?
|
|
} else {
|
|
max_cands[0]
|
|
};
|
|
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.state = CandidateState::Elected;
|
|
state.num_elected += 1;
|
|
count_card.order_elected = state.num_elected as isize;
|
|
|
|
state.logger.log_smart(
|
|
template1,
|
|
template2,
|
|
vec![candidate.name.as_str()]
|
|
);
|
|
|
|
if constraints::update_constraints(state, opts) {
|
|
// Recheck as some candidates may have been doomed
|
|
hopefuls = state.election.candidates.iter()
|
|
.filter(|c| {
|
|
let cc = &state.candidates[c];
|
|
return cc.state == CandidateState::Hopeful || cc.state == CandidateState::Guarded;
|
|
})
|
|
.collect();
|
|
} else {
|
|
hopefuls.remove(hopefuls.iter().position(|c| *c == candidate).unwrap());
|
|
}
|
|
}
|
|
|
|
return Ok(());
|
|
}
|
|
|
|
/// Declare all continuing candidates elected, if the number equals the number of remaining vacancies
|
|
///
|
|
/// Returns `true` if any candidates were elected.
|
|
fn bulk_elect<N: Number>(state: &mut CountState<N>, opts: &STVOptions) -> Result<bool, STVError> {
|
|
if can_bulk_elect(state, 0) {
|
|
state.title = StageKind::BulkElection;
|
|
do_bulk_elect(state, opts, "{} is elected to fill the remaining vacancy.", "{} are elected to fill the remaining vacancies.")?;
|
|
return Ok(true);
|
|
}
|
|
return Ok(false);
|
|
}
|
|
|
|
/// Declare all doomed candidates excluded
|
|
///
|
|
/// Returns `true` if any candidates were excluded.
|
|
fn exclude_doomed<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<bool, STVError>
|
|
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>,
|
|
{
|
|
let doomed: Vec<&Candidate> = state.election.candidates.iter() // Present in order in case of tie
|
|
.filter(|c| state.candidates[c].state == CandidateState::Doomed)
|
|
.collect();
|
|
|
|
if !doomed.is_empty() {
|
|
let excluded_candidates;
|
|
if opts.bulk_exclude {
|
|
excluded_candidates = doomed;
|
|
} else {
|
|
// Exclude only the lowest-ranked doomed candidate
|
|
let min_cands = ties::multiple_min_by(&doomed, |c| &state.candidates[c].votes);
|
|
excluded_candidates = if min_cands.len() > 1 {
|
|
vec![choose_lowest(state, opts, &min_cands, "Which candidate to exclude?")?]
|
|
} else {
|
|
vec![min_cands[0]]
|
|
};
|
|
}
|
|
|
|
let names: Vec<&str> = excluded_candidates.iter().map(|c| c.name.as_str()).sorted().collect();
|
|
state.title = StageKind::ExclusionOf(excluded_candidates.clone());
|
|
state.logger.log_smart(
|
|
"Doomed candidate, {}, is excluded.",
|
|
"Doomed candidates, {}, are excluded.",
|
|
names
|
|
);
|
|
|
|
if opts.early_bulk_elect {
|
|
// Determine if the proposed exclusion would enable a bulk election
|
|
// See comment in exclude_hopefuls as to constraints
|
|
if can_bulk_elect(state, excluded_candidates.len()) {
|
|
// Exclude candidates without further transfers
|
|
let order_excluded = state.num_excluded + 1;
|
|
for candidate in excluded_candidates {
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.state = CandidateState::Excluded;
|
|
state.num_excluded += 1;
|
|
count_card.order_elected = -(order_excluded as isize);
|
|
}
|
|
|
|
do_bulk_elect(state, opts, "As a result of the proposed exclusion, {} is elected to fill the remaining vacancy.", "As a result of the proposed exclusion, {} are elected to fill the remaining vacancies.")?;
|
|
return Ok(true);
|
|
}
|
|
}
|
|
|
|
exclude_candidates(state, opts, excluded_candidates, "Exclusion")?;
|
|
return Ok(true);
|
|
}
|
|
|
|
return Ok(false);
|
|
}
|
|
|
|
/// Determine which continuing candidates have votes equal to or below the minimum threshold
|
|
fn hopefuls_below_threshold<'a, N: Number>(state: &CountState<'a, N>, opts: &STVOptions) -> Vec<&'a Candidate> {
|
|
let min_threshold = N::parse(&opts.min_threshold);
|
|
|
|
let excluded_candidates: Vec<&Candidate> = state.candidates.iter()
|
|
.filter_map(|(c, cc)|
|
|
if cc.state == CandidateState::Hopeful && cc.votes <= min_threshold {
|
|
Some(c)
|
|
} else {
|
|
None
|
|
})
|
|
.collect();
|
|
|
|
// Do not exclude if this violates constraints
|
|
match constraints::test_constraints_any_time(state, &excluded_candidates, CandidateState::Excluded) {
|
|
Ok(_) => { return excluded_candidates; }
|
|
Err(_) => { return Vec::new(); } // Bulk exclusion conflicts with constraints
|
|
}
|
|
}
|
|
|
|
/// Determine which continuing candidates could be excluded in a bulk exclusion
|
|
///
|
|
/// The value of [STVOptions::bulk_exclude] is not taken into account and must be handled by the caller.
|
|
fn hopefuls_to_bulk_exclude<'a, N: Number>(state: &CountState<'a, N>, _opts: &STVOptions) -> Vec<&'a Candidate> {
|
|
let mut excluded_candidates = Vec::new();
|
|
|
|
let mut hopefuls: Vec<(&Candidate, &CountCard<N>)> = state.candidates.iter()
|
|
.filter(|(_, cc)| cc.state == CandidateState::Hopeful)
|
|
.collect();
|
|
|
|
// Sort by votes
|
|
// NB: Unnecessary to handle ties, as ties will be rejected at "Do not exclude if this could change the order of exclusion"
|
|
hopefuls.sort_unstable_by(|a, b| a.1.votes.cmp(&b.1.votes));
|
|
|
|
let total_surpluses = state.total_surplus();
|
|
|
|
// Attempt to exclude as many candidates as possible
|
|
for i in 0..hopefuls.len() {
|
|
let try_exclude = &hopefuls[0..hopefuls.len()-i];
|
|
|
|
// Do not exclude if this leaves insufficient candidates
|
|
if state.num_elected + hopefuls.len() - try_exclude.len() < state.election.seats {
|
|
continue;
|
|
}
|
|
|
|
// Do not exclude if this could change the order of exclusion
|
|
let total_votes = state.total_votes_of(try_exclude.iter().map(|(_, cc)| *cc));
|
|
if i != 0 && total_votes + &total_surpluses >= hopefuls[hopefuls.len()-i].1.votes {
|
|
continue;
|
|
}
|
|
|
|
let try_exclude: Vec<&Candidate> = try_exclude.iter().map(|(c, _)| *c).collect();
|
|
|
|
// Do not exclude if this violates constraints
|
|
match constraints::test_constraints_any_time(state, &try_exclude, CandidateState::Excluded) {
|
|
Ok(_) => {}
|
|
Err(_) => { break; } // Bulk exclusion conflicts with constraints
|
|
}
|
|
|
|
excluded_candidates.extend(try_exclude);
|
|
break;
|
|
}
|
|
|
|
return excluded_candidates;
|
|
}
|
|
|
|
/// Exclude the lowest-ranked hopeful candidate(s)
|
|
fn exclude_hopefuls<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<(), STVError>
|
|
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>,
|
|
{
|
|
let mut excluded_candidates: Vec<&Candidate> = Vec::new();
|
|
|
|
if state.num_excluded == 0 {
|
|
if opts.bulk_exclude && opts.min_threshold == "0" {
|
|
// Proceed directly to bulk exclusion, as candidates with 0 votes will necessarily be included
|
|
} else {
|
|
// Exclude candidates below min threshold
|
|
excluded_candidates = hopefuls_below_threshold(state, opts);
|
|
}
|
|
}
|
|
|
|
// Attempt a bulk exclusion
|
|
if excluded_candidates.is_empty() && opts.bulk_exclude {
|
|
excluded_candidates = hopefuls_to_bulk_exclude(state, opts);
|
|
}
|
|
|
|
// Exclude lowest ranked candidate
|
|
if excluded_candidates.is_empty() {
|
|
let hopefuls: Vec<&Candidate> = state.election.candidates.iter() // Present in order in case of tie
|
|
.filter(|c| state.candidates[c].state == CandidateState::Hopeful)
|
|
.collect();
|
|
|
|
let min_cands = ties::multiple_min_by(&hopefuls, |c| &state.candidates[c].votes);
|
|
excluded_candidates = if min_cands.len() > 1 {
|
|
vec![choose_lowest(state, opts, &min_cands, "Which candidate to exclude?")?]
|
|
} else {
|
|
vec![min_cands[0]]
|
|
};
|
|
}
|
|
|
|
let names: Vec<&str> = excluded_candidates.iter().map(|c| c.name.as_str()).sorted().collect();
|
|
state.title = StageKind::ExclusionOf(excluded_candidates.clone());
|
|
if state.election.seats == 1 {
|
|
state.logger.log_smart(
|
|
"No candidate has a majority, so {} is excluded.",
|
|
"No candidate has a majority, so {} are excluded.",
|
|
names
|
|
);
|
|
} else {
|
|
state.logger.log_smart(
|
|
"No surpluses to distribute, so {} is excluded.",
|
|
"No surpluses to distribute, so {} are excluded.",
|
|
names
|
|
);
|
|
}
|
|
|
|
if opts.early_bulk_elect {
|
|
// Determine if the proposed exclusion would enable a bulk election
|
|
// This should be OK for constraints, as if the election of the remaining candidates would be invalid, the excluded candidate must necessarily have be guarded already
|
|
if can_bulk_elect(state, excluded_candidates.len()) {
|
|
// Exclude candidates without further transfers
|
|
let order_excluded = state.num_excluded + 1;
|
|
for candidate in excluded_candidates {
|
|
let count_card = state.candidates.get_mut(candidate).unwrap();
|
|
count_card.state = CandidateState::Excluded;
|
|
state.num_excluded += 1;
|
|
count_card.order_elected = -(order_excluded as isize);
|
|
}
|
|
|
|
do_bulk_elect(state, opts, "As a result of the proposed exclusion, {} is elected to fill the remaining vacancy.", "As a result of the proposed exclusion, {} are elected to fill the remaining vacancies.")?;
|
|
return Ok(());
|
|
}
|
|
}
|
|
|
|
exclude_candidates(state, opts, excluded_candidates, "Exclusion")?;
|
|
return Ok(());
|
|
}
|
|
|
|
/// Continue the exclusion of a candidate who is being excluded
|
|
///
|
|
/// Returns `true` if an exclusion was continued.
|
|
fn continue_exclusion<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<bool, STVError>
|
|
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>,
|
|
{
|
|
// Cannot filter by raw vote count, as candidates may have 0.00 votes but still have recorded ballot papers
|
|
let mut excluded_with_votes: Vec<(&Candidate, &CountCard<N>)> = state.candidates.iter()
|
|
.filter(|(_, cc)| cc.state == CandidateState::Excluded && !cc.finalised)
|
|
.collect();
|
|
|
|
if !excluded_with_votes.is_empty() {
|
|
excluded_with_votes.sort_unstable_by(|a, b| a.1.order_elected.cmp(&b.1.order_elected));
|
|
|
|
let order_excluded = excluded_with_votes[0].1.order_elected;
|
|
let excluded_candidates: Vec<&Candidate> = excluded_with_votes.into_iter()
|
|
.filter(|(_, cc)| cc.order_elected == order_excluded)
|
|
.map(|(c, _)| c)
|
|
.collect();
|
|
|
|
let names: Vec<&str> = excluded_candidates.iter().map(|c| c.name.as_str()).sorted().collect();
|
|
state.title = StageKind::ExclusionOf(excluded_candidates.clone());
|
|
state.logger.log_smart(
|
|
"Continuing exclusion of {}.",
|
|
"Continuing exclusion of {}.",
|
|
names
|
|
);
|
|
|
|
exclude_candidates(state, opts, excluded_candidates, "Exclusion")?;
|
|
return Ok(true);
|
|
}
|
|
|
|
return Ok(false);
|
|
}
|
|
|
|
/// Perform one stage of a candidate exclusion, according to [STVOptions::exclusion]
|
|
pub fn exclude_candidates<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions, excluded_candidates: Vec<&'a Candidate>, complete_type: &'static str) -> Result<(), STVError>
|
|
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>,
|
|
{
|
|
match opts.exclusion {
|
|
ExclusionMethod::SingleStage => {
|
|
match opts.surplus {
|
|
SurplusMethod::WIG | SurplusMethod::UIG | SurplusMethod::EG => {
|
|
gregory::exclude_candidates(state, opts, excluded_candidates, complete_type);
|
|
}
|
|
SurplusMethod::Meek => {
|
|
meek::exclude_candidates(state, opts, excluded_candidates);
|
|
}
|
|
SurplusMethod::IHare | SurplusMethod::Hare => {
|
|
sample::exclude_candidates(state, opts, excluded_candidates)?;
|
|
}
|
|
}
|
|
}
|
|
ExclusionMethod::ByValue | ExclusionMethod::FirstPreferencesThenByValue | ExclusionMethod::BySource | ExclusionMethod::ParcelsByOrder => {
|
|
// Segmented exclusion compatible only with Gregory method
|
|
gregory::exclude_candidates(state, opts, excluded_candidates, complete_type);
|
|
}
|
|
ExclusionMethod::ResetAndReiterate => {
|
|
gregory::exclude_candidates_and_reset(state, opts, excluded_candidates);
|
|
}
|
|
}
|
|
|
|
return Ok(());
|
|
}
|
|
|
|
/// Determine if the count is complete because the number of elected candidates equals the number of vacancies
|
|
fn finished_before_stage<N: Number>(state: &CountState<N>) -> bool {
|
|
if state.num_elected >= state.election.seats {
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Break a tie between the given candidates according to [STVOptions::ties], selecting the highest candidate
|
|
///
|
|
/// The given candidates are assumed to be tied in this round.
|
|
pub fn choose_highest<'c, N: Number>(state: &mut CountState<N>, opts: &STVOptions, candidates: &[&'c Candidate], prompt_text: &str) -> Result<&'c Candidate, STVError> {
|
|
for strategy in opts.ties.iter() {
|
|
match strategy.choose_highest(state, opts, candidates, prompt_text) {
|
|
Ok(c) => {
|
|
return Ok(c);
|
|
}
|
|
Err(e) => {
|
|
if let STVError::UnresolvedTie = e {
|
|
continue;
|
|
} else {
|
|
return Err(e);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return Err(STVError::UnresolvedTie);
|
|
}
|
|
|
|
/// Break a tie between the given candidates according to [STVOptions::ties], selecting the lowest candidate
|
|
///
|
|
/// The given candidates are assumed to be tied in this round.
|
|
pub fn choose_lowest<'c, N: Number>(state: &mut CountState<N>, opts: &STVOptions, candidates: &[&'c Candidate], prompt_text: &str) -> Result<&'c Candidate, STVError> {
|
|
for strategy in opts.ties.iter() {
|
|
match strategy.choose_lowest(state, opts, candidates, prompt_text) {
|
|
Ok(c) => {
|
|
return Ok(c);
|
|
}
|
|
Err(e) => {
|
|
if let STVError::UnresolvedTie = e {
|
|
continue;
|
|
} else {
|
|
return Err(e);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return Err(STVError::UnresolvedTie);
|
|
}
|
|
|
|
/// If required, initialise the state of the forwards or backwards tie-breaking strategies, according to [STVOptions::ties]
|
|
fn init_tiebreaks<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
|
|
if !opts.ties.iter().any(|t| t == &TieStrategy::Forwards) && !opts.ties.iter().any(|t| t == &TieStrategy::Backwards) {
|
|
return;
|
|
}
|
|
|
|
// Sort candidates in this stage by votes, grouping by ties
|
|
let mut sorted_candidates: Vec<(&Candidate, &CountCard<N>)> = state.candidates.iter().collect();
|
|
sorted_candidates.sort_unstable_by(|a, b| a.1.votes.cmp(&b.1.votes));
|
|
let sorted_candidates: Vec<Vec<(&Candidate, &CountCard<N>)>> = sorted_candidates.into_iter()
|
|
.group_by(|(_, cc)| &cc.votes)
|
|
.into_iter()
|
|
.map(|(_, candidates)| candidates.collect())
|
|
.collect();
|
|
|
|
// Update forwards tie-breaking order
|
|
if opts.ties.iter().any(|t| t == &TieStrategy::Forwards) {
|
|
let mut hm = CandidateMap::with_capacity(state.candidates.len());
|
|
for (i, group) in sorted_candidates.iter().enumerate() {
|
|
for (candidate, _) in group.iter() {
|
|
hm.insert(candidate, i);
|
|
}
|
|
}
|
|
state.forwards_tiebreak = Some(hm);
|
|
}
|
|
|
|
// Update backwards tie-breaking order
|
|
if opts.ties.iter().any(|t| t == &TieStrategy::Backwards) {
|
|
let mut hm = CandidateMap::with_capacity(state.candidates.len());
|
|
for (i, group) in sorted_candidates.iter().enumerate() {
|
|
for (candidate, _) in group.iter() {
|
|
hm.insert(candidate, i);
|
|
}
|
|
}
|
|
state.backwards_tiebreak = Some(hm);
|
|
}
|
|
}
|
|
|
|
/// If required, update the state of the forwards or backwards tie-breaking strategies, according to [STVOptions::ties]
|
|
fn update_tiebreaks<N: Number>(state: &mut CountState<N>, _opts: &STVOptions) {
|
|
if state.forwards_tiebreak.is_none() && state.backwards_tiebreak.is_none() {
|
|
return;
|
|
}
|
|
|
|
// Sort candidates in this stage by votes, grouping by ties
|
|
let mut sorted_candidates: Vec<(&Candidate, &CountCard<N>)> = state.candidates.iter().collect();
|
|
sorted_candidates.sort_unstable_by(|a, b| a.1.votes.cmp(&b.1.votes));
|
|
let sorted_candidates: Vec<Vec<&Candidate>> = sorted_candidates.into_iter()
|
|
.group_by(|(_, cc)| &cc.votes)
|
|
.into_iter()
|
|
.map(|(_, candidates)| candidates.map(|(c, _)| c).collect())
|
|
.collect();
|
|
|
|
// Update forwards tie-breaking order
|
|
if let Some(hm) = state.forwards_tiebreak.as_mut() {
|
|
// TODO: Check if already completely sorted
|
|
let mut sorted_last_round: Vec<(&Candidate, &usize)> = hm.iter().collect();
|
|
sorted_last_round.sort_unstable_by(|a, b| a.1.cmp(b.1));
|
|
let sorted_last_round: Vec<Vec<&Candidate>> = sorted_last_round.into_iter()
|
|
.group_by(|(_, v)| **v)
|
|
.into_iter()
|
|
.map(|(_, group)| group.map(|(c, _)| c).collect())
|
|
.collect();
|
|
|
|
let mut i: usize = 0;
|
|
for mut group in sorted_last_round.into_iter() {
|
|
if group.len() == 1 {
|
|
hm.insert(group[0], i);
|
|
i += 1;
|
|
continue;
|
|
} else {
|
|
// Tied in last round - refer to this round
|
|
group.sort_unstable_by(|a, b|
|
|
sorted_candidates.iter().position(|x| x.contains(a)).unwrap()
|
|
.cmp(&sorted_candidates.iter().position(|x| x.contains(b)).unwrap())
|
|
);
|
|
let tied_last_round = group.into_iter()
|
|
.group_by(|c| sorted_candidates.iter().position(|x| x.contains(c)).unwrap());
|
|
|
|
for (_, group2) in tied_last_round.into_iter() {
|
|
for candidate in group2 {
|
|
hm.insert(candidate, i);
|
|
}
|
|
i += 1;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Update backwards tie-breaking order
|
|
if let Some(hm) = state.backwards_tiebreak.as_mut() {
|
|
let hm_orig = hm.clone();
|
|
let mut i: usize = 0;
|
|
for group in sorted_candidates.iter() {
|
|
if group.len() == 1 {
|
|
hm.insert(group[0], i);
|
|
i += 1;
|
|
continue;
|
|
} else {
|
|
// Tied in this round - refer to last round
|
|
let mut tied_this_round: Vec<&Candidate> = group.iter().copied().collect();
|
|
tied_this_round.sort_unstable_by(|a, b| hm_orig[a].cmp(&hm_orig[b]));
|
|
let tied_this_round = tied_this_round.into_iter()
|
|
.group_by(|c| hm_orig[c]);
|
|
|
|
for (_, group2) in tied_this_round.into_iter() {
|
|
for candidate in group2 {
|
|
hm.insert(candidate, i);
|
|
}
|
|
i += 1;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Returns `true` if the votes required for election should be displayed, based on the given [STVOptions]
|
|
pub fn should_show_vre(opts: &STVOptions) -> bool {
|
|
if opts.quota_mode == QuotaMode::ERS97 || opts.quota_mode == QuotaMode::ERS76 {
|
|
return true;
|
|
}
|
|
if opts.surplus == SurplusMethod::Meek && opts.quota_mode == QuotaMode::DynamicByTotal {
|
|
// Meek method ensures that, if the quota is recalculated, every candidate will be elected with a quota
|
|
return false;
|
|
}
|
|
if opts.early_bulk_elect {
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|