Improve performance of Scottish STV

Remove reliance on normalising ballot papers

docs/options.md

@@ -196,7 +196,7 @@ In the BLT file format, each set of preferences can have a specified weight –
 
 When ballots are not normalised (default), a set of preferences with weight *n* > 1 is represented as a single ballot with value *n*. This is known as [list-packed ballots](http://www.votingmatters.org.uk/ISSUE21/I21P1.pdf).
 
-When ballots are normalised, a set of preferences with weight *n* > 1 is instead converted to *n* ballots each with value 1. This is generally required only when the rules directly deal with individual ballot values, such as when *Sum surplus transfers* is set to *Per ballot*.
+When ballots are normalised, a set of preferences with weight *n* > 1 is instead converted to *n* ballots each with value 1.
 
 ## Count optimisations
 

html/index.js

@@ -438,7 +438,7 @@ function changePreset() {
 		document.getElementById('selNumbers').value = 'fixed';
 		document.getElementById('txtDP').value = '5';
 		document.getElementById('txtPPDP').value = '5';
-		document.getElementById('chkNormaliseBallots').checked = true;
+		document.getElementById('chkNormaliseBallots').checked = false;
 		document.getElementById('chkRoundQuota').checked = true;
 		document.getElementById('txtRoundQuota').value = '0';
 		document.getElementById('chkRoundVotes').checked = false;

src/stv/gregory.rs

@@ -226,15 +226,19 @@ where
 		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 = &vote.ballot.orig_value * &reweight_value_fraction(orig_value_fraction, surplus, is_weighted, surplus_fraction, surplus_denom, opts.round_surplus_fractions);
+				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;
 			}
-			//state.logger.log_literal(format!("Transferring {:.0} ballot papers, totalling {:.dps$} votes.", entry.num_ballots, entry.num_votes, dps=opts.pp_decimals));
 			return result;
 		}
 	}

tests/scotland.rs

@@ -32,7 +32,7 @@ fn scotland_linn07_fixed5() {
 		//.round_votes(Some(5))
 		.round_quota(Some(0))
 		.sum_surplus_transfers(stv::SumSurplusTransfersMode::PerBallot)
-		.normalise_ballots(true)
+		//.normalise_ballots(true)
 		.quota_criterion(stv::QuotaCriterion::GreaterOrEqual)
 		.early_bulk_elect(false)
 		.pp_decimals(5)
@@ -50,7 +50,7 @@ fn scotland_linn07_gfixed5() {
 		.round_votes(Some(5))
 		.round_quota(Some(0))
 		.sum_surplus_transfers(stv::SumSurplusTransfersMode::PerBallot)
-		.normalise_ballots(true)
+		//.normalise_ballots(true)
 		.quota_criterion(stv::QuotaCriterion::GreaterOrEqual)
 		.early_bulk_elect(false)
 		.pp_decimals(5)