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Implement TransferTable for surpluses (WIP)

This commit is contained in:
RunasSudo 2021-09-11 02:43:11 +10:00
parent fbdc32ba30
commit 056242514d
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GPG Key ID: 7234E476BF21C61A
8 changed files with 182 additions and 180 deletions
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9
src/numbers/fixed.rs
View File

@ -206,9 +206,7 @@ impl ops::Sub for Fixed {
impl ops::Mul for Fixed {
type Output = Self;
fn mul(self, _rhs: Self) -> Self::Output {
todo!()
}
fn mul(self, rhs: Self) -> Self::Output { Self(self.0 * rhs.0 / get_factor()) }
}
impl ops::Div for Fixed {
@ -294,8 +292,9 @@ impl ops::MulAssign<&Self> for Fixed {
}
impl ops::DivAssign<&Self> for Fixed {
fn div_assign(&mut self, _rhs: &Self) {
todo!()
fn div_assign(&mut self, rhs: &Self) {
self.0 *= get_factor();
self.0 /= &rhs.0;
}
}

9
src/numbers/gfixed.rs
View File

@ -238,9 +238,7 @@ impl ops::Sub for GuardedFixed {
impl ops::Mul for GuardedFixed {
type Output = Self;
fn mul(self, _rhs: Self) -> Self::Output {
todo!()
}
fn mul(self, rhs: Self) -> Self::Output { Self(self.0 * rhs.0 / get_factor())}
}
impl ops::Div for GuardedFixed {
@ -326,8 +324,9 @@ impl ops::MulAssign<&Self> for GuardedFixed {
}
impl ops::DivAssign<&Self> for GuardedFixed {
fn div_assign(&mut self, _rhs: &Self) {
todo!()
fn div_assign(&mut self, rhs: &Self) {
self.0 *= get_factor();
self.0 /= &rhs.0;
}
}

8
src/numbers/native.rs
View File

@ -109,9 +109,7 @@ impl ops::Sub for NativeFloat64 {
impl ops::Mul for NativeFloat64 {
type Output = NativeFloat64;
fn mul(self, _rhs: Self) -> Self::Output {
todo!()
}
fn mul(self, rhs: Self) -> Self::Output { Self(self.0 * rhs.0) }
}
impl ops::Div for NativeFloat64 {
@ -188,9 +186,7 @@ impl ops::MulAssign<&NativeFloat64> for NativeFloat64 {
}
impl ops::DivAssign<&NativeFloat64> for NativeFloat64 {
fn div_assign(&mut self, _rhs: &NativeFloat64) {
todo!()
}
fn div_assign(&mut self, rhs: &NativeFloat64) { self.0 /= &rhs.0; }
}
impl ops::RemAssign<&NativeFloat64> for NativeFloat64 {

8
src/numbers/rational_num.rs
View File

@ -186,9 +186,7 @@ impl ops::Sub for Rational {
impl ops::Mul for Rational {
type Output = Rational;
fn mul(self, _rhs: Self) -> Self::Output {
todo!()
}
fn mul(self, rhs: Self) -> Self::Output { Self(self.0 * rhs.0) }
}
impl ops::Div for Rational {
@ -265,9 +263,7 @@ impl ops::MulAssign<&Rational> for Rational {
}
impl ops::DivAssign<&Rational> for Rational {
fn div_assign(&mut self, _rhs: &Rational) {
todo!()
}
fn div_assign(&mut self, rhs: &Rational) { self.0 /= &rhs.0 }
}
impl ops::RemAssign<&Rational> for Rational {

8
src/numbers/rational_rug.rs
View File

@ -185,9 +185,7 @@ impl ops::Sub for Rational {
impl ops::Mul for Rational {
type Output = Self;
fn mul(self, _rhs: Self) -> Self::Output {
todo!()
}
fn mul(self, rhs: Self) -> Self::Output { Self(self.0 * rhs.0) }
}
impl ops::Div for Rational {
@ -264,9 +262,7 @@ impl ops::MulAssign<&Self> for Rational {
}
impl ops::DivAssign<&Self> for Rational {
fn div_assign(&mut self, _rhs: &Self) {
todo!()
}
fn div_assign(&mut self, rhs: &Self) { self.0 /= &rhs.0 }
}
impl ops::RemAssign<&Self> for Rational {

173
src/stv/gregory.rs
View File

@ -15,7 +15,7 @@
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
use super::{ExclusionMethod, NextPreferencesEntry, STVError, STVOptions, SumSurplusTransfersMode, SurplusMethod, SurplusOrder};
use super::{ExclusionMethod, STVError, STVOptions, SurplusMethod, SurplusOrder};
use super::sample;
use crate::constraints;
@ -25,7 +25,6 @@ use crate::stv::transfers::TransferTable;
use crate::ties;
use std::cmp::max;
use std::collections::HashMap;
use std::ops;
/// Distribute first preference votes according to the Gregory method
@ -168,97 +167,23 @@ where
/// Return the denominator of the surplus fraction
///
/// Returns `None` if the value of transferable votes <= surplus (i.e. all transferable votes are transferred at values received).
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>
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, opts: &STVOptions) -> Option<N>
where
for<'r> &'r N: ops::Sub<&'r N, Output=N>
{
if transferable_only {
let transferable_units = if weighted { transferable_votes } else { transferable_ballots };
if opts.transferable_only {
let transferable_units = if opts.surplus.is_weighted() { transferable_votes } else { transferable_ballots };
if transferable_votes > surplus {
return Some(transferable_units);
return Some(transferable_units.clone());
} else {
return None;
}
} else {
if weighted {
return Some(total_votes);
if opts.surplus.is_weighted() {
return Some(total_votes.clone());
} else {
return Some(total_ballots);
}
}
}
/// Return the reweighted value fraction of a parcel/vote after being transferred
fn reweight_value_fraction<N: Number>(
value_fraction: &N,
surplus: &N,
weighted: bool,
surplus_fraction: &Option<N>,
surplus_denom: &Option<&N>,
round_tvs: Option<usize>) -> N
{
let result;
match surplus_denom {
Some(v) => {
if let Some(_) = round_tvs {
// Rounding requested: use the rounded transfer value
if weighted {
result = value_fraction.clone() * surplus_fraction.as_ref().unwrap();
} else {
result = surplus_fraction.as_ref().unwrap().clone();
}
} else {
// Avoid unnecessary rounding error by first multiplying by the surplus
if weighted {
result = value_fraction.clone() * surplus / *v;
} else {
result = surplus.clone() / *v;
}
}
}
None => {
result = value_fraction.clone();
}
}
return result;
}
/// Compute the number of votes to credit to a continuing candidate during a surplus transfer, based on [STVOptions::sum_surplus_transfers]
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
where
for<'r> &'r N: ops::Mul<&'r N, Output=N>,
for<'r> &'r N: ops::Div<&'r N, Output=N>,
{
match opts.sum_surplus_transfers {
SumSurplusTransfersMode::ByValue => {
// Calculate transfer across all votes in this parcel
let mut result = N::new();
for vote in entry.votes.iter() {
result += &vote.ballot.orig_value;
}
result *= reweight_value_fraction(orig_value_fraction, surplus, is_weighted, surplus_fraction, surplus_denom, opts.round_surplus_fractions);
return result;
}
SumSurplusTransfersMode::PerBallot => {
// Sum transfer per each individual ballot
// TODO: This could be moved to distribute_surplus to avoid looping over the votes and calculating transfer values twice
let mut new_value_fraction = reweight_value_fraction(orig_value_fraction, surplus, is_weighted, surplus_fraction, surplus_denom, opts.round_surplus_fractions);
if let Some(dps) = opts.round_votes {
new_value_fraction.floor_mut(dps);
}
let mut result = N::new();
for vote in entry.votes.iter() {
let mut vote_value = &new_value_fraction * &vote.ballot.orig_value;
if let Some(dps) = opts.round_votes {
vote_value.floor_mut(dps);
}
result += vote_value;
}
return result;
return Some(total_ballots.clone());
}
}
}
@ -320,13 +245,7 @@ where
parcels_next_prefs.push((parcel.value_fraction, result));
}
// Calculate surplus fraction
let is_weighted = match opts.surplus {
SurplusMethod::WIG => { true }
SurplusMethod::UIG | SurplusMethod::EG => { false }
_ => unreachable!()
};
// Calculate and print surplus fraction
let total_ballots = &transferable_ballots + &exhausted_ballots;
let total_votes = &transferable_votes + &exhausted_votes;
@ -334,15 +253,20 @@ where
let count_card = state.candidates.get_mut(elected_candidate).unwrap();
count_card.ballot_transfers = -&total_ballots;
let surplus_denom = calculate_surplus_denom(&surplus, &transferable_ballots, &transferable_votes, &total_ballots, &total_votes, is_weighted, opts.transferable_only);
let mut surplus_denom = calculate_surplus_denom(&surplus, &transferable_ballots, &transferable_votes, &total_ballots, &total_votes, opts);
let surplus_numer;
let mut surplus_fraction;
match surplus_denom {
match &surplus_denom {
Some(v) => {
surplus_fraction = Some(surplus.clone() / v);
// Round down if requested
if let Some(dps) = opts.round_surplus_fractions {
surplus_fraction.as_mut().unwrap().floor_mut(dps);
surplus_numer = surplus_fraction.clone();
surplus_denom = None;
} else {
surplus_numer = Some(surplus.clone());
}
if opts.transferable_only {
@ -361,6 +285,8 @@ where
}
None => {
surplus_fraction = None;
surplus_numer = None;
surplus_denom = None;
// This can only happen if --transferable-only
if transferable_ballots == N::one() {
@ -373,41 +299,44 @@ where
// Reweight and transfer parcels
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();
let mut transfer_table = TransferTable::new();
for (value_fraction, result) in parcels_next_prefs {
for (candidate, entry) in result.candidates.into_iter() {
// Record transfers
// TODO: Is there a better way of writing this?
let transfers_orig = candidate_transfers.remove(candidate).unwrap();
let transfers_add = sum_surplus_transfers(&entry, &value_fraction, &surplus, is_weighted, &surplus_fraction, &surplus_denom, state, opts);
candidate_transfers.insert(candidate, transfers_orig + transfers_add);
transfer_table.add_transfers(&value_fraction, candidate, &entry.num_ballots);
let mut new_value_fraction;
if opts.surplus.is_weighted() {
new_value_fraction = value_fraction.clone();
new_value_fraction *= surplus_numer.as_ref().unwrap(); // Guaranteed to be Some in WIGM
if let Some(n) = &surplus_denom {
new_value_fraction /= n;
}
} else {
if let Some(sf) = &surplus_fraction {
new_value_fraction = sf.clone();
} else {
new_value_fraction = value_fraction.clone();
}
}
if let Some(dps) = opts.round_values {
new_value_fraction.floor_mut(dps);
}
// Transfer candidate votes
let parcel = Parcel {
votes: entry.votes,
value_fraction: reweight_value_fraction(&value_fraction, &surplus, is_weighted, &surplus_fraction, &surplus_denom, opts.round_surplus_fractions),
value_fraction: new_value_fraction,
source_order: state.num_elected + state.num_excluded,
};
let count_card = state.candidates.get_mut(candidate).unwrap();
count_card.ballot_transfers += parcel.num_ballots();
count_card.parcels.push(parcel);
}
// Record exhausted votes
if opts.transferable_only {
if transferable_votes > surplus {
// No ballots exhaust
} else {
exhausted_transfers += &surplus - &transferable_votes;
}
} else {
exhausted_transfers += sum_surplus_transfers(&result.exhausted, &value_fraction, &surplus, is_weighted, &surplus_fraction, &surplus_denom, state, opts);
}
transfer_table.add_exhausted(&value_fraction, &result.exhausted.num_ballots);
// Transfer exhausted votes
let parcel = Parcel {
@ -415,29 +344,13 @@ where
value_fraction: value_fraction, // TODO: Reweight exhausted votes
source_order: state.num_elected + state.num_excluded,
};
state.exhausted.ballot_transfers += parcel.num_ballots();
state.exhausted.parcels.push(parcel);
}
let mut checksum = N::new();
// 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;
checksum += transfer_table.apply_to(state, opts, Some(&surplus), &surplus_numer, &surplus_denom);
// Finalise candidate votes
let count_card = state.candidates.get_mut(elected_candidate).unwrap();
@ -690,7 +603,7 @@ where
}
// Credit transferred votes
checksum += transfer_table.apply_to(state, opts);
checksum += transfer_table.apply_to(state, opts, None, &None, &None);
if !votes_remain {
// Finalise candidate votes

9
src/stv/mod.rs
View File

@ -403,6 +403,15 @@ impl SurplusMethod {
SurplusMethod::Hare => "--surplus hare",
}.to_string()
}
/// Returns `true` if this is a weighted method
pub fn is_weighted(&self) -> bool {
return match self {
SurplusMethod::WIG => { true }
SurplusMethod::UIG | SurplusMethod::EG => { false }
_ => unreachable!()
};
}
}
impl<S: AsRef<str>> From<S> for SurplusMethod {

136
src/stv/transfers.rs
View File

@ -15,7 +15,7 @@
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
use super::STVOptions;
use super::{STVOptions, SumSurplusTransfersMode};
use crate::election::{Candidate, CountState};
use crate::numbers::Number;
@ -74,8 +74,9 @@ impl<'e, N: Number> TransferTable<'e, N> {
/// Apply the transfers described in the table to the count sheet
///
/// Credit continuing candidates and exhausted pile with the appropriate number of ballot papers and votes.
pub fn apply_to(&self, state: &mut CountState<N>, opts: &STVOptions) -> N {
// TODO: SumSurplusTransfers
pub fn apply_to(&self, state: &mut CountState<N>, opts: &STVOptions, surplus: Option<&N>, surplus_numer: &Option<N>, surplus_denom: &Option<N>) -> N {
// Use weighted rules if exclusion or WIGM
let is_weighted = surplus.is_none() || opts.surplus.is_weighted();
let mut checksum = N::new();
@ -84,13 +85,73 @@ impl<'e, N: Number> TransferTable<'e, N> {
let mut votes_transferred = N::new();
let mut ballots_transferred = N::new();
for column in self.columns.iter() {
if let Some(cell) = column.cells.get(*candidate) {
votes_transferred += cell.ballots.clone() * &column.value_fraction;
ballots_transferred += &cell.ballots;
// If exclusion, or surplus at present value, or SumSurplusTransfersMode::ByValue
if surplus_numer.is_none() || opts.sum_surplus_transfers == SumSurplusTransfersMode::ByValue {
// Calculate transfer across all votes in this parcel
for column in self.columns.iter() {
if let Some(cell) = column.cells.get(*candidate) {
if is_weighted {
votes_transferred += cell.ballots.clone() * &column.value_fraction;
}
ballots_transferred += &cell.ballots;
}
}
if !is_weighted {
votes_transferred = ballots_transferred.clone();
}
// If surplus, multiply by surplus fraction
if let Some(n) = &surplus_numer {
votes_transferred *= n;
}
if let Some(n) = &surplus_denom {
votes_transferred /= n;
}
} else if opts.sum_surplus_transfers == SumSurplusTransfersMode::PerBallot {
// Sum transfer per each individual ballot
for column in self.columns.iter() {
if let Some(cell) = column.cells.get(*candidate) {
ballots_transferred += &cell.ballots;
let mut new_value_fraction;
if is_weighted {
new_value_fraction = column.value_fraction.clone();
// If surplus, multiply by surplus fraction
if let Some(n) = &surplus_numer {
new_value_fraction *= n;
}
if let Some(n) = &surplus_denom {
new_value_fraction /= n;
}
// Round if required
if let Some(dps) = opts.round_values {
new_value_fraction.floor_mut(dps);
}
} else {
if let Some(n) = &surplus_numer {
new_value_fraction = n.clone();
} else {
// Transferred at original value
new_value_fraction = column.value_fraction.clone();
}
if let Some(n) = &surplus_denom {
new_value_fraction /= n;
}
// Round if required
if let Some(dps) = opts.round_values {
new_value_fraction.floor_mut(dps);
}
}
votes_transferred += cell.ballots.clone() * new_value_fraction;
}
}
} else {
unreachable!();
}
// Round if required
if let Some(dps) = opts.round_votes {
votes_transferred.floor_mut(dps);
}
@ -102,23 +163,56 @@ impl<'e, N: Number> TransferTable<'e, N> {
}
// Credit exhausted votes
let mut votes_transferred = N::new();
let mut ballots_transferred = N::new();
// If exclusion or not --transferable-only
if surplus.is_none() || !opts.transferable_only {
// Standard rules
let mut votes_transferred = N::new();
let mut ballots_transferred = N::new();
for column in self.columns.iter() {
votes_transferred += column.exhausted.ballots.clone() * &column.value_fraction;
ballots_transferred += &column.exhausted.ballots;
for column in self.columns.iter() {
if is_weighted {
votes_transferred += column.exhausted.ballots.clone() * &column.value_fraction;
}
ballots_transferred += &column.exhausted.ballots;
}
if !is_weighted {
votes_transferred = ballots_transferred.clone();
}
// If surplus, multiply by surplus fraction
if let Some(n) = &surplus_numer {
votes_transferred *= n;
}
if let Some(n) = &surplus_denom {
votes_transferred /= n;
}
// Round if required
if let Some(dps) = opts.round_votes {
votes_transferred.floor_mut(dps);
}
state.exhausted.transfer(&votes_transferred);
state.exhausted.ballot_transfers += ballots_transferred;
checksum += votes_transferred;
} else {
// Credit only nontransferable difference
if surplus_numer.is_none() {
// TODO: Is there a purer way of calculating this?
let difference = surplus.unwrap().clone() - &checksum;
state.exhausted.transfer(&difference);
checksum += difference;
for column in self.columns.iter() {
state.exhausted.ballot_transfers += &column.exhausted.ballots;
}
} else {
// No ballots exhaust
}
}
if let Some(dps) = opts.round_votes {
votes_transferred.floor_mut(dps);
}
state.exhausted.transfer(&votes_transferred);
state.exhausted.ballot_transfers += ballots_transferred;
checksum += votes_transferred;
return checksum;
}
}