X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=blobdiff_plain;f=stv;h=3c6160e979f27ffa7f026ed59d20a4b2dabf2710;hp=3942b6b175f488c6dbbedfd6338ded2560eb450c;hb=163ff5fe92d09360697b9ca48e792e50625f5c0d;hpb=be8af598391869fa6bb4cf9ccf630a09f6c2edd8

diff --git a/stv b/stv
index 3942b6b..3c6160e 100755
--- a/stv
+++ b/stv
@@ -3,6 +3,19 @@
 # Does STV according to
 #  http://www.rosenstiel.co.uk/stvrules/av/index.htm
 
+# Usage:
+#  ./stv [TIEBREAK ...] PLACES [INPUT-FILES ...]
+#
+# PLACES is the number of seats to be filled
+#
+# INPUT-FILES are in the format:
+#    VOTER PQRST
+# where P, Q, R, etc. are candidates.  Candidates
+# must be single letters.
+#
+# Each TIEBREAK is
+#   P,Q,... 
+
 use strict;
 use utf8;
 use autodie;
@@ -20,6 +33,25 @@ use List::MoreUtils qw(nsort_by);
 our $stage=0;
 our @allvotes;
 
+our %tiebreak; # $tiebreak{ winningcand }{ losingcand } = 1
+
+while (@ARGV && $ARGV[0] =~ m/[<>]/) {
+    my ($losers, $winners) = ($? eq '<' ? ($`, $') : ($', $`));
+    my @losers = sort split /\,/, $losers;
+    my @winners = sort split /\,/, $winners;
+    die "@losers @winners" if @losers>1 && @winners>1;
+    my @all = sort @losers, @winners;
+    my $record = sub {
+	my ($how, $howers) = @_;
+	return unless @$howers == 1;
+	die "@all $how" if defined $tiebreak{$how}{"@all"};
+	$tiebreak{$how}{"@all"} = $howers->[0];
+    };
+    $record->('winner', \@winners);
+    $record->('loser',  \@losers);
+    shift @ARGV;
+}    
+
 our $places = shift @ARGV;
 die unless $places eq ($places + 0);
 
@@ -95,18 +127,36 @@ sub equalpiles ($@) {
 
 sub historically_prefer ($@) {
     my ($signum, @choices) = @_;
+    # $signum==+1 means choose candidates with more early preferences
 
     return $choices[0] if @choices < 2;
 
     my $compare = sub {
 	foreach my $sr (@stagerecord) {
-	    my $d = $sr->{ $a->{Cand} } <=> $sr->{ $b->{Cand} };
-	    return $d * $signum if $d;
+	    my $d = ($sr->{ $a->{Cand} }//0) <=> ($sr->{ $b->{Cand} }//0);
+	    return -$d * $signum if $d;
 	}
 	return 0;
     };
 
     @choices = sort $compare @choices;
+
+    print DEBUG "historically_prefer\n",
+	Data::Dumper->Dump([\@choices, \@stagerecord],
+			   [qw(_@choices _@stagerecord)]);
+
+    foreach my $s (@choices) {
+	my $c = $s->{Cand};
+	printf " %6s %10s |", 'tiebrk', $c;
+	foreach my $sr (@stagerecord) {
+	    my $p = pr($sr->{$c} // 0);
+	    $p =~ s/\.0+\b//g;
+	    $p =~ s/ //g;
+	    print "$p|";
+	}
+	print "\n";
+    }
+
     $a = $choices[0];
     my $numequal = 1;
     for (;;) {
@@ -116,7 +166,17 @@ sub historically_prefer ($@) {
 	$numequal++;
     }
 
-    die 'random choice unimplemented' if $numequal > 1;
+    if ($numequal > 1) {
+	my $how = $signum > 0 ? 'winner' : 'loser';
+        my @all = sort map { $_->{Cand} } @choices[ 0 .. $numequal-1 ];
+	my $hower = $tiebreak{$how}{"@all"};
+	if (defined $hower) {
+	    printf "%7.7s %10s !!!!!!!!!!\n", "TIE".(uc $how), $hower;
+	    return grep { $_->{Cand} eq $hower } @choices;
+	}
+	die "need tie break for $how between @all\n";
+    }
+
     return $choices[0];
 }
 
@@ -161,7 +221,7 @@ for (;;) {
     }
     my @sorted;
     my $things_update = sub {
-	foreach my $s (@surpluses, values %sorted) {
+	foreach my $s (values %sorted) {
 	    $s->{Total} = sum0 map { $_->{Weight} } @{ $s->{Votes } };
 	}
 	@sorted = nsort_by { -$_->{Total} } values %sorted;
@@ -205,6 +265,7 @@ for (;;) {
 	my $topvoters = $s->{Total};
 	my $surplus = $topvoters - $quota;
 	last unless $surplus >= 0;
+	last unless $placesremain;
 
 	my @elect = equalpiles 'elect?', @sorted;
 
@@ -226,6 +287,7 @@ for (;;) {
 	    push @newsurpluses, $s;
 	    delete $sorted{ $s->{Cand} };
 	    delete $continuing{ $s->{Cand} };
+	    $placesremain--;
 	}
 
 	$things_update->();
@@ -245,15 +307,18 @@ for (;;) {
 	    grep { !!voteliveprefs $_ }
 	    @$votes;
 
+	my $derate = 1/1;
 	printf "%7s %10s %s\n", 'xfrable', $s->{Cand}, pr $transferrable;
 	if ($transferrable > $surplus) {
-	    my $derate = $transferrable / $surplus;
+	    $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;
 	    }
 	}
+	$s->{Total} = $transferrable / $derate;
+
 	push @surpluses, $s;
 
 	$things_update->();
@@ -346,4 +411,14 @@ for (;;) {
     push @unsorted, @$votes;
 }
 
+open VL, ">.stv.votes" or die $!;
+foreach my $vote (@allvotes) {
+    print VL "----------------------------------------\n";
+    print VL "voter $vote->{Voter}\n";
+    print VL "prefs ". (join " ", @{ $vote->{Prefs} }). "\n";
+    print VL $_, "\n" foreach @{ $vote->{Log} };
+}
+print VL "========================================\n";
+close VL;
+
 print "done.\n";