Better error messages when insufficient candidates to fill vacancies

This commit is contained in:
RunasSudo 2021-09-05 22:31:34 +10:00
parent 0a7189e54f
commit 09c4a375a7
Signed by: RunasSudo
GPG Key ID: 7234E476BF21C61A
5 changed files with 125 additions and 9 deletions

View File

@ -553,12 +553,14 @@ impl<S: AsRef<str>> From<S> for ConstraintMode {
}
/// An error during the STV count
#[derive(Debug)]
#[derive(Debug, Eq, PartialEq)]
pub enum STVError {
/// Options for the count are invalid
InvalidOptions(&'static str),
/// Tie could not be resolved
UnresolvedTie,
/// Unrecoverable error during the count
CannotCompleteCount(&'static str),
}
impl STVError {
@ -567,6 +569,7 @@ impl STVError {
match self {
STVError::InvalidOptions(s) => s,
STVError::UnresolvedTie => "Unable to resolve tie",
STVError::CannotCompleteCount(s) => s,
}
}
}
@ -667,6 +670,14 @@ where
return Ok(false);
}
// Sanity check
let num_hopefuls = state.candidates.values()
.filter(|cc| cc.state == CandidateState::Hopeful)
.count();
if num_hopefuls == 0 {
return Err(STVError::CannotCompleteCount("Insufficient continuing candidates to complete count"));
}
// Exclude lowest hopeful
exclude_hopefuls(state, &opts)?; // Cannot fail
calculate_quota(state, opts);
@ -960,9 +971,11 @@ fn elect_sure_winners<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOp
}
});
let last_winner = hopefuls[num_vacancies - 1].1;
if last_winner.votes <= total_trailing {
return Ok(false);
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();
@ -973,7 +986,7 @@ fn elect_sure_winners<'a, N: Number>(state: &mut CountState<'a, N>, opts: &STVOp
}
// Bulk elect all leading candidates
while state.num_elected < state.election.seats {
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?")?
@ -1151,7 +1164,7 @@ fn can_bulk_elect<N: Number>(state: &CountState<N>, num_to_exclude: usize) -> bo
})
.count();
if state.num_elected + num_hopefuls - num_to_exclude <= state.election.seats {
if num_hopefuls > 0 && state.num_elected + num_hopefuls - num_to_exclude <= state.election.seats {
return true;
}
return false;

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@ -0,0 +1,14 @@
# Comment: Constructed example - insufficient candidates to fill vacancies
5 7
1 1 0
1 2 0
1 3 0
1 4 0
1 5 0
0
"Candidate 1"
"Candidate 2"
"Candidate 3"
"Candidate 4"
"Candidate 5"
"Insufficient candidates example 1"

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@ -0,0 +1,17 @@
# Comment: Constructed example - insufficient candidates after the exclusion of those with no votes
8 7
1 1 0
1 2 0
1 3 0
1 4 0
1 5 0
0
"Candidate 1"
"Candidate 2"
"Candidate 3"
"Candidate 4"
"Candidate 5"
"Candidate 6"
"Candidate 7"
"Candidate 8"
"Insufficient candidates example 2"

74
tests/units.rs Normal file
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@ -0,0 +1,74 @@
/* 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/>.
*/
mod utils;
use opentally::election::{CountState, Election};
use opentally::numbers::Rational;
use opentally::parser::blt;
use opentally::stv;
use opentally::ties::TieStrategy;
#[test]
fn insufficient_candidates1() {
let stv_opts = stv::STVOptionsBuilder::default()
.ties(vec![TieStrategy::Random(String::new())])
.build().unwrap();
let mut election: Election<Rational> = blt::parse_path("tests/data/insufficient_candidates1.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) => { assert_eq!(done, false); }
Err(err) => {
assert_eq!(err, stv::STVError::CannotCompleteCount("Insufficient continuing candidates to complete count"));
break;
}
}
}
}
#[test]
fn insufficient_candidates2() {
let stv_opts = stv::STVOptionsBuilder::default()
.ties(vec![TieStrategy::Random(String::new())])
.build().unwrap();
let mut election: Election<Rational> = blt::parse_path("tests/data/insufficient_candidates2.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) => { assert_eq!(done, false); }
Err(err) => {
assert_eq!(err, stv::STVError::CannotCompleteCount("Insufficient continuing candidates to complete count"));
break;
}
}
}
}

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@ -65,9 +65,7 @@ where
for<'r> &'r N: ops::Div<&'r N, Output=N>,
for<'r> &'r N: ops::Neg<Output=N>,
{
if stv_opts.normalise_ballots {
election.normalise_ballots();
}
stv::preprocess_election(&mut election, &stv_opts);
// Initialise count state
let mut state = CountState::new(&election);