Implement support for equal rankings

README.md

@@ -24,6 +24,7 @@ OpenTally is highly customisable, including options for:
 * calculations using fixed-point arithmetic, guarded fixed-point ([quasi-exact](http://www.votingmatters.org.uk/ISSUE24/I24P2.pdf)) or exact rational numbers
 * different tie breaking rules (backwards, random, manual) with auditable deterministic random number generation
 * multiple constraints (e.g. affirmative action rules)
+* equal rankings
 
 ## Online usage
 

docs/blt.md

@@ -9,9 +9,9 @@ The file format is as follows:
 -2
 3 1 3 4 0
 4 1 3 2 0
-2 4 1 3 0
+2 4 1=3 0
 1 2 0
-2 2 4 3 1 0
+2 2=4=3 1 0
 1 3 4 2 0
 0
 "Adam"
@@ -25,7 +25,7 @@ The first line (`4 2`) indicates that there are 4 candidates for 2 vacancies.
 
 The second line (`-2`), which is optional, indicates that the 2nd candidate (Basil) has withdrawn. Multiple withdrawn candidates may be specified on this line, e.g. `-2 -3 -4`.
 
-The third line (second, if there are no withdrawn candidates) begins the ballot data. `3 1 3 4 0` indicates that there were 3 ballots which voted, in order of preference, for the 1st candidate (Adam), then the 3rd candidate (Charlotte), then the 4th candidate (Donald). A `0` optionally indicates the end of the list of preferences.
+The third line (second, if there are no withdrawn candidates) begins the ballot data. `3 1 3 4 0` indicates that there were 3 ballots which voted, in order of preference, for the 1st candidate (Adam), then the 3rd candidate (Charlotte), then the 4th candidate (Donald). An `=` indicates that multiple candidates were ranked at the same preference. A `0` optionally indicates the end of the list of preferences.
 
 The end of the list of ballots must be indicated with a single `0`.
 

html/index.js

@@ -29,7 +29,7 @@ var tblResult = document.getElementById('result');
 var divLogs2 = document.getElementById('resultLogs2');
 var olStageComments;
 
-var worker = new Worker('worker.js');
+var worker = new Worker('worker.js?v=GITVERSION');
 
 worker.onmessage = function(evt) {
 	if (evt.data.type === 'init') {

html/worker.js

@@ -1,4 +1,4 @@
-importScripts('opentally.js');
+importScripts('opentally.js?v=GITVERSION');
 
 var wasm = wasm_bindgen;
 var wasmRaw;
@@ -9,7 +9,7 @@ const DATA_START = DATA_ADDR + 8;
 const DATA_END = 50 * 1024; // Needs to be increased compared with Asyncify default
 
 async function initWasm() {
-	wasmRaw = await wasm_bindgen('opentally_async.wasm');
+	wasmRaw = await wasm_bindgen('opentally_async.wasm?v=GITVERSION');
 	
 	new Int32Array(wasmRaw.memory.buffer, DATA_ADDR).set([DATA_START, DATA_END]);
 	

src/election.rs

@@ -24,6 +24,8 @@ use crate::stv::{QuotaMode, STVOptions};
 #[cfg(not(target_arch = "wasm32"))]
 use rkyv::{Archive, Archived, Deserialize, Fallible, Resolver, Serialize, with::{ArchiveWith, DeserializeWith, SerializeWith}};
 
+use itertools::Itertools;
+
 use std::cmp::max;
 use std::collections::HashMap;
 
@@ -414,11 +416,27 @@ impl<N: Number> Ballot<N> {
 		
 		for preference in self.preferences.iter() {
 			if preference.len() == 1 {
+				// Single preference so just add to the end of existing preferences
 				for minivoter in minivoters.iter_mut() {
 					minivoter.push(preference.clone());
 				}
 			} else {
-				todo!();
+				// Equal ranking
+				// Get all possible permutations
+				let permutations: Vec<Vec<usize>> = preference.iter().copied().permutations(preference.len()).collect();
+				
+				// Split into new "minivoters" for each possible permutation
+				let mut new_minivoters = Vec::with_capacity(minivoters.len() * permutations.len());
+				for permutation in permutations {
+					for minivoter in minivoters.iter() {
+						let mut new_minivoter = minivoter.clone();
+						for p in permutation.iter() {
+							new_minivoter.push(vec![*p]);
+						}
+						new_minivoters.push(new_minivoter);
+					}
+				}
+				minivoters = new_minivoters;
 			}
 		}
 		

src/parser/blt.rs

@@ -144,13 +144,19 @@ impl<N: Number, I: Iterator<Item=char>> BLTParser<N, I> {
 		self.delimiter_not_nl();
 		
 		// Read preferences
-		let mut preferences = Vec::new();
+		let mut preferences: Vec<Vec<usize>> = Vec::new();
 		loop {
 			if self.lookahead() == '0' || self.lookahead() == '\n' {
 				// End of preferences
 				self.accept();
 				break;
+			} else if self.lookahead() == '=' {
+				// Equal preference
+				self.accept();
+				preferences.last_mut().unwrap().push(self.usize()? - 1);
+				self.delimiter_not_nl();
 			} else {
+				// No equal preference
 				preferences.push(vec![self.usize()? - 1]);
 				self.delimiter_not_nl();
 			}

src/parser/csp.rs

@@ -19,6 +19,7 @@ use crate::election::{Ballot, Candidate, Election};
 use crate::numbers::Number;
 
 use csv::ReaderBuilder;
+use itertools::Itertools;
 
 use std::collections::HashMap;
 use std::io::Read;
@@ -82,12 +83,21 @@ pub fn parse_reader<R: Read, N: Number>(reader: R) -> Election<N> {
 		}
 		
 		// Sort by ranking
-		// FIXME: Handle equal rankings and skipped rankings
-		preferences.sort_by(|a, b| a.0.cmp(&b.0));
+		let mut unique_rankings: Vec<usize> = preferences.iter().map(|(r, _)| *r).unique().collect();
+		unique_rankings.sort();
+		
+		let mut sorted_preferences = Vec::with_capacity(preferences.len());
+		for ranking in unique_rankings {
+			// Filter for preferences at this ranking
+			let prefs_this_ranking: Vec<usize> = preferences.iter()
+				.filter_map(|(r, i)| if *r == ranking { Some(**i) } else { None })
+				.collect();
+			sorted_preferences.push(prefs_this_ranking);
+		}
 		
 		ballots.push(Ballot {
 			orig_value: value,
-			preferences: preferences.into_iter().map(|(_, i)| vec![*i]).collect(),
+			preferences: sorted_preferences,
 		});
 	}
 	

tests/data/equal_ranks.blt

@@ -0,0 +1,15 @@
+# Comment: Test data featuring equal rankings
+# Source: RunasSudo
+# Contributor: RunasSudo
+7 4
+1 1 2=3=4 5 6=7 0
+1 5=6=7 0
+0
+"Candidate 1"
+"Candidate 2"
+"Candidate 3"
+"Candidate 4"
+"Candidate 5"
+"Candidate 6"
+"Candidate 7"
+"Test data featuring equal rankings"

tests/equal_ranks.rs

@@ -0,0 +1,28 @@
+/*  OpenTally: Open-source election vote counting
+ *  Copyright © 2021 Lee Yingtong Li (RunasSudo)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+use opentally::election::Election;
+use opentally::numbers::Rational;
+use opentally::parser;
+
+#[test]
+fn parse_equal_ranks() {
+	let mut election: Election<Rational> = parser::blt::parse_path("tests/data/equal_ranks.blt").expect("Parse Error");
+	election.realise_equal_rankings();
+	
+	assert_eq!(election.ballots.len(), 18);
+}