From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 1 Aug 2016 15:28:44 +0000 (+0100)
Subject: stv: correct surplus transfer value
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=commitdiff_plain;h=16858a6757d2b921469a29d4974dbd1f7c221e1d;hp=0328306e06758d9fb43cec21611d044eda1acf09;ds=sidebyside

stv: correct surplus transfer value
---

diff --git a/stv b/stv
index fbd7b41..111b2bd 100755
--- a/stv
+++ b/stv
@@ -140,7 +140,7 @@ for (;;) {
     my $placesremain = $places - @elected;
 
     unless ($placesremain > 0) {
-	printf "Complete.\n";
+	printf "Complete: @elected\n";
 	last;
     }
 
@@ -194,6 +194,8 @@ for (;;) {
 
     my $need_to_transfer_surplus = 1;
 
+    my @newsurpluses;
+
     # Look for people to elect.
     # We elect as many as we can, rather than recomputing the (lower) quota
     # (ERS rules 5.4.9)
@@ -206,17 +208,43 @@ for (;;) {
 	printf "%7s %10s ***************\n", 'ELECTED', $s->{Cand};
 	push @elected, $s->{Cand};
 
-	my $derate = $topvoters / $surplus;
-	printf "%7s %10s %s\n", 'derate', $s->{Cand}, pr $derate;
-
 	foreach my $vote (@{ $s->{Votes} }) {
-	    votelog $vote, "elected $s->{Cand}, derated $derate";
-	    $vote->{Weight} /= $derate;
+	    votelog $vote, "elected $s->{Cand}";
 	}
-	push @surpluses, $s;
+
+	$s->{Surplus} = $surplus;
+	push @newsurpluses, $s;
 	delete $sorted{ $s->{Cand} };
 	delete $continuing{ $s->{Cand} };
 
+	$things_update->();
+    }
+
+    foreach my $s (@newsurpluses) {
+	# calculate the transfer value of each surplus
+	# we do this simultaneously, but based on the number of
+	# continuing candidates (excluding all the ones elected already)
+	# ERS rule 5.3.3
+
+	my $votes = $s->{Votes};
+	my $surplus = $s->{Surplus};
+	my $transferrable =
+	    sum0
+	    map { $_->{Weight} }
+	    grep { !!voteliveprefs $_ }
+	    @$votes;
+
+	printf "%7s %10s %s\n", 'xfrable', $s->{Cand}, pr $transferrable;
+	if ($transferrable > $surplus) {
+	    my $derate = $transferrable / $surplus;
+	    printf "%7s %10s %s\n", 'derate', $s->{Cand}, pr $derate;
+	    foreach my $vote (@{ $s->{Votes} }) {
+		votelog $vote, "part of surplus, derated ". pr $derate;
+		$vote->{Weight} /= $derate;
+	    }
+	}
+	push @surpluses, $s;
+
 	$things_update->();
 	printf "%7s %10s %s\n", 'surplus', $s->{Cand}, pr $s->{Total};