OpenTally/tests/scotland.rs

/*  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/>.
 */

// https://web.archive.org/web/20121004213938/http://www.glasgow.gov.uk/en/YourCouncil/Elections_Voting/Election_Results/ElectionScotland2007/LGWardResults.htm?ward=1&wardname=1%20-%20Linn

use opentally::election::{CandidateState, CountState, Election};
use opentally::numbers::Fixed;
use opentally::stv;

use num_traits::Zero;
use xmltree::Element;

use std::io::{self, BufRead};
use std::fs::File;

#[test]
fn scotland_linn07_fixed5() {
	let stv_opts = stv::STVOptions {
		round_tvs: Some(5),
		round_weights: None,
		round_votes: None,
		round_quota: Some(0),
		sum_surplus_transfers: stv::SumSurplusTransfersMode::PerBallot,
		quota: stv::QuotaType::Droop,
		quota_criterion: stv::QuotaCriterion::GreaterOrEqual,
		quota_mode: stv::QuotaMode::Static,
		surplus: stv::SurplusMethod::WIG,
		surplus_order: stv::SurplusOrder::BySize,
		transferable_only: false,
		exclusion: stv::ExclusionMethod::SingleStage,
		bulk_exclude: false,
		defer_surpluses: false,
		pp_decimals: 5,
	};
	Fixed::set_dps(5);
	
	// Read XML file
	let file = File::open("tests/data/linn07.xml").expect("IO Error");
	let root = Element::parse(file).expect("Parse Error");
	
	let mut candidates: Vec<&Element> = root.children.iter()
		.filter_map(|n| match n {
			xmltree::XMLNode::Element(e) => if e.name == "candidate" { Some(e) } else { None },
			_ => None,
		})
		.collect();
	let cand_nt = candidates.pop().unwrap();
	
	// TODO: Validate candidate names
	
	let num_stages = root.get_child("headerrow").expect("Syntax Error").children.len();
	
	// Read BLT
	let file = File::open("tests/data/linn07.blt").expect("IO Error");
	let file_reader = io::BufReader::new(file);
	let lines = file_reader.lines();
	
	let election: Election<Fixed> = Election::from_blt(lines.map(|r| r.expect("IO Error").to_string()).into_iter());
	
	// Initialise count state
	let mut state = CountState::new(&election);
	
	// Distribute first preferences
	stv::count_init(&mut state, &stv_opts);
	let mut stage_num = 1;
	
	for i in 0..num_stages {
		println!("Stage {}", stage_num);
		
		// Validate NT
		let nt_votes = get_cand_stage(cand_nt, i)
			.get_child("value").unwrap()
			.get_text().unwrap()
			.to_string();
		
		assert!(approx_eq(&(&state.exhausted.votes + &state.loss_fraction.votes), &parse_str(nt_votes)));
		
		for (candidate, cand_xml) in state.election.candidates.iter().zip(candidates.iter()) {
			let count_card = state.candidates.get(candidate).unwrap();
			
			// Validate candidate votes
			let cand_votes = get_cand_stage(cand_xml, i)
				.get_child("value").unwrap()
				.get_text().unwrap()
				.to_string();
			let cand_votes = parse_str(cand_votes);
			assert!(approx_eq(&count_card.votes, &cand_votes), "Failed to validate votes for candidate {}. Expected {:}, got {:}", candidate.name, cand_votes, count_card.votes);
			
			// Validate candidate states
			let cand_state = get_cand_stage(cand_xml, i)
				.get_child("status").unwrap()
				.get_text().unwrap()
				.to_string();
			if cand_state == "Continuing" {
				assert!(count_card.state == CandidateState::HOPEFUL);
			} else if cand_state == "Elected" {
				assert!(count_card.state == CandidateState::ELECTED);
			} else if cand_state == "Excluded" {
				assert!(count_card.state == CandidateState::EXCLUDED);
			} else {
				panic!("Unknown state descriptor {}", cand_state);
			}
		}
		
		assert_eq!(stv::count_one_stage(&mut state, &stv_opts), false);
		stage_num += 1;
	}
	
	assert_eq!(stv::count_one_stage(&mut state, &stv_opts), true);
}

fn get_cand_stage(candidate: &Element, idx: usize) -> &Element {
	return candidate.children.iter()
		.filter_map(|n| match n {
			xmltree::XMLNode::Element(e) => if e.name == "stage" { Some(e) } else { None },
			_ => None,
		})
		.nth(idx).unwrap();
}

fn parse_str(s: String) -> Fixed {
	if s == "-" { return Fixed::zero(); }
	let f: f64 = s.parse().expect("Syntax Error");
	return opentally::numbers::From::from(f);
}

fn approx_eq(a: &Fixed, b: &Fixed) -> bool {
	// Some tolerance required in equality comparisons, as eSTV incorrectly computes transfers
	// by value, instead of all at once, resulting in increased rounding error
	let eq_tol: Fixed = opentally::numbers::From::from(0.0001);
	
	if a - b > eq_tol {
		return false;
	}
	if b - a > eq_tol {
		return false;
	}
	return true;
}