Fix bugs

Fix bug excluding-by-value/source candidates with no votes
Fix bug electing too many candidates if more reach the quota than vacancies remain
Add regression test

src/stv/gregory.rs

@@ -496,7 +496,9 @@ where
 		}
 		ExclusionMethod::ByValue => {
 			// Exclude by value
-			let excluded_with_votes: Vec<&&Candidate> = excluded_candidates.iter().filter(|c| !state.candidates[*c].finalised).collect();
+			let excluded_with_votes: Vec<&&Candidate> = excluded_candidates.iter()
+				.filter(|c| { let cc = &state.candidates[*c]; !cc.finalised && !cc.parcels.is_empty() })
+				.collect();
 			
 			if excluded_with_votes.is_empty() {
 				votes_remain = false;
@@ -554,7 +556,9 @@ where
 		}
 		ExclusionMethod::BySource => {
 			// Exclude by source candidate
-			let excluded_with_votes: Vec<&&Candidate> = excluded_candidates.iter().filter(|c| !state.candidates[*c].finalised).collect();
+			let excluded_with_votes: Vec<&&Candidate> = excluded_candidates.iter()
+				.filter(|c| { let cc = &state.candidates[*c]; !cc.finalised && !cc.parcels.is_empty() })
+				.collect();
 			
 			if excluded_with_votes.is_empty() {
 				votes_remain = false;

src/stv/mod.rs

@@ -939,11 +939,12 @@ fn meets_vre<N: Number>(state: &CountState<N>, count_card: &CountCard<N>, opts:
 ///
 /// Returns `true` if any candidates were elected.
 fn elect_sure_winners<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOptions) -> Result<bool, STVError> {
-	let num_vacancies = state.election.seats - state.num_elected;
+	if state.num_elected >= state.election.seats {
-	if num_vacancies == 0 {
 		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)
@@ -1033,7 +1034,7 @@ fn elect_hopefuls<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOption
 	
 	let elected = !cands_meeting_quota.is_empty();
 	
-	while !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 {

tests/data/A33.blt

@@ -0,0 +1,17 @@
+# Comment: BY STV
+# Comment: Number of truncated papers:  0
+# Comment: AKA R038 in Wichmann's database
+# Source: Nicolaus Tideman via Warren D Smith <https://rangevoting.org/TidemanData.html>
+# Contributor: RunasSudo
+18 3
+1 15 9 5 6 8 0
+1 18 7 16 1 12 14 0
+1 14 9 17 13 15 5 2 12 16 8 0
+1 6 5 3 4 15 12 9 7 1 14 13 16 18 17 8 2 10 11 0
+1 12 1 17 9 6 5 2 0
+1 15 8 5 3 0
+1 8 15 2 3 5 4 1 9 0
+1 3 5 1 4 11 2 8 0
+1 17 4 9 14 16 6 1 13 8 15 3 18 5 12 11 10 2 7 0
+0
+"A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "f:a33"

tests/special_cases.rs

@@ -17,12 +17,13 @@
 
 mod utils;
 
-use opentally::election::{CountState, Election};
+use opentally::election::{CandidateState, CountState, Election};
 use opentally::numbers::Rational;
 use opentally::parser::blt;
 use opentally::stv;
 use opentally::ties::TieStrategy;
 
+/// Insufficient candidates to fill all vacancies
 #[test]
 fn insufficient_candidates1() {
 	let stv_opts = stv::STVOptionsBuilder::default()
@@ -48,6 +49,7 @@ fn insufficient_candidates1() {
 	}
 }
 
+/// After bulk exclusion of candidates with no votes, insufficient candidates remain to fill all vacancies
 #[test]
 fn insufficient_candidates2() {
 	let stv_opts = stv::STVOptionsBuilder::default()
@@ -72,3 +74,42 @@ fn insufficient_candidates2() {
 		}
 	}
 }
+
+/// Tideman A33 election: exclusion of candidate with no votes; more candidates reach the quota than vacancies
+#[test]
+fn tideman_a33_ers97_rational() {
+	let stv_opts = stv::STVOptionsBuilder::default()
+		.round_surplus_fractions(Some(2))
+		.round_values(Some(2))
+		.round_votes(Some(2))
+		.round_quota(Some(2))
+		.quota(stv::QuotaType::DroopExact)
+		.quota_criterion(stv::QuotaCriterion::GreaterOrEqual)
+		.quota_mode(stv::QuotaMode::ERS97)
+		.ties(vec![TieStrategy::Random(String::new("20210908"))])
+		.surplus(stv::SurplusMethod::EG)
+		.transferable_only(true)
+		.exclusion(stv::ExclusionMethod::ByValue)
+		.early_bulk_elect(false)
+		.bulk_exclude(true)
+		.defer_surpluses(true)
+		.build().unwrap();
+	
+	let mut election: Election<Rational> = blt::parse_path("tests/data/A33.blt").expect("Syntax Error");
+	stv::preprocess_election(&mut election, &stv_opts);
+	
+	let mut state = CountState::new(&election);
+	
+	stv::count_init(&mut state, &stv_opts).unwrap();
+	
+	loop {
+		let result = stv::count_one_stage::<Rational>(&mut state, &stv_opts);
+		match result {
+			Ok(done) => { if done { break; } }
+			Err(err) => { panic!("{}", err); }
+		}
+	}
+	
+	let num_winners = state.candidates.values().filter(|cc| cc.state == CandidateState::Elected).count();
+	assert_eq!(num_winners, 3);
+}