X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=blobdiff_plain;f=compute-scottish-stv;h=6fde10308b409753d9f877e1df709300d2558fa3;hp=e3d5d7770a6b9f81ea701ddb58c3bd444e8dcf4c;hb=a4f2fc687bb9e16c33a59619acafe2cc21833ee1;hpb=781d40da5cf41034debb17d3b7f4f62d5665a97e;ds=sidebyside

diff --git a/compute-scottish-stv b/compute-scottish-stv
index e3d5d77..6fde103 100755
--- a/compute-scottish-stv
+++ b/compute-scottish-stv
@@ -4,6 +4,9 @@
 # The Scottish Local Government Elections Order 2007
 
 use strict;
+use Carp;
+use Data::Dumper;
+use Math::BigRat;
 use bigrat;
 
 # Data structures:
@@ -29,6 +32,18 @@ our $stage=0;
 our $quota;
 our %tie;
 
+open DEBUG, ">.compute.log" or die $!;
+DEBUG->autoflush(1);
+
+$SIG{__WARN__} = sub {
+    print DEBUG Dumper(\%tie,
+		       \@non_transferable,
+		       \%cands,
+		       \@allvotes,
+		       $stage, $quota);
+    confess $_[0];
+};
+
 sub unkopt ($$) {
     my ($what,$opt) = @_;
     if ($opt =~ m/^[A-Z]/) {
@@ -55,12 +70,12 @@ for (;;) {
 	    }
 	}
     } elsif (m/^(\w+) = (\S*) \|/) {
-	my ($cand,$desc) = @_;
+	my ($cand,$desc) = ($1,$2);
 	unkopt "candidate $cand", $_ foreach split / /, $';
 	$cands{$cand}{Desc} = $desc;
     } elsif (m/^(\w*) :\s*(.*)\s*\|(.*)/) {
 	my ($voter,$prefs,$opts) = ($1,$2,$3);
-	my $v = { Voter => $voter };
+	my $v = { Voter => $voter, Prefs => [ ] };
 	push @{ $v->{Prefs} }, [ $_ =~ m/\w+/g ]
 	    foreach split /\s+/, $prefs;
 	foreach $_ (split / /, $opts) {
@@ -81,12 +96,15 @@ for (;;) {
 }
 
 $cands{$_}{Cand} = $_ foreach keys %cands;
+$_->{Weight} //= 1/1 foreach @allvotes;
+$_->{TransferredSurplus} //= [ ] foreach @allvotes;
 
 sub votelog ($$) {
     my ($vote,$m) = @_;
     push @{ $vote->{Log} }, "stage $stage: $m";
 }
 
+sub sortballots (@);
 sub sortballots (@) {
     # Takes each argument, which should be a ballot, sorts
     # it into $cand{CAND}{Votes} according to first preference.
@@ -118,7 +136,7 @@ sub sortballots (@) {
 	my $noncont = $c->{NonCont};
 	if ($noncont) {
 	    votelog $v, "dropping pref $fp, $noncont";
-	    sortvallots $v;
+	    sortballots $v;
 	    next;
 	}
 	votelog $v, "sorted into pile for candidate $fp weight $w";
@@ -128,7 +146,7 @@ sub sortballots (@) {
 
 sub prf {
     my $fmt = shift;
-    printf "stage %d: ".$_, $stage, @_;
+    printf "stage %d: ".$fmt, $stage, @_;
 }
 
 sub countballots () {
@@ -136,22 +154,23 @@ sub countballots () {
 	my $c = $cands{$cand};
 	next if $c->{NonCont};
 	$c->{Total} = 0;
-	$c->{Total} += $_->{Weight} foreach @{ $c->{Voters} };
-	prf "cand %s: %s votes\n", $stage, $cand, $c->{Total};
+	$c->{Total} += $_->{Weight} foreach @{ $c->{Votes} };
+	prf "candidate %-10s: %10s votes\n", $cand, $c->{Total};
 	$c->{History}[$stage-1] = $c->{Total};
     }
 }
 
 sub computequota () {
     my $totalvalid = 0;
-    $totalvalid += $_->{Total} foreach keys %cands;
-    $quota = floor($totalvalid / (1 + $seats));
+    $totalvalid += $_->{Total} foreach values %cands;
+    $quota = ($totalvalid / (1 + $seats)) -> bfloor();
+    prf "quota %10s\n", $quota;
 }
 
 sub total_history_cmp () {
     my $ha = $a->{History};
     my $hb = $b->{History};
-    foreach my $s (reverse 1 .. $stage) {
+    foreach my $s (reverse 0 .. $stage-1) {
 	my $d = $ha->[$s] <=> $hb->[$s];
 	next unless $d;
 	print DEBUG "history cmp $a->{Cand} $b->{Cand}".
@@ -206,13 +225,14 @@ sub select_best_worst ($$$$) {
     if ($nequal > 1) {
 	my @all = map { $_->{Cand} } @maybe[0 .. $nequal-1];
 	my $tiekey = $signum > 0 ? 'Win' : 'Lose';
-	my $win = $tie{"@all"}{$tiekey};
-	die "need tie break, want $tiekey from @all" unless defined $win;
+	$selectcand = $tie{"@all"}{$tiekey};
+	die "need tie break, want $tiekey from @all"
+	    unless defined $selectcand;
 	prf "$what %s due to tie break amongst %s\n",
 	    $selectcand, "@all";
     } else {
-	$selectcand = $maybe[0];
-	prf "$what %s\n";
+	$selectcand = $maybe[0]{Cand};
+	prf "$what %s\n", $selectcand;
     }
 
     return $cands{$selectcand};
@@ -224,13 +244,17 @@ sub elect_core ($) {
     $c->{NonCont} = 'Elected';
 }
 
+$stage = 1;
+
 sortballots @allvotes;
+countballots();
+computequota();
 
 for (;;) {
     $stage++;
 
     my $seats_remain = $seats
-	- grep { $_->{NonCont} eq 'Elected' } values %cands;
+	- grep { ($_->{NonCont} // '') eq 'Elected' } values %cands;
     if (continuing() <= $seats_remain) {
 	foreach my $c (continuing()) {
 	    prf "electing %s to fill remaining place(s)\n", $c->{Cand};
@@ -258,16 +282,30 @@ for (;;) {
 	    next;
 	}
 
-	my $B = $c->{Weight};
+	my $B = $c->{Total};
+	my %tspr;
+
+	prf "surplus %10s\n", $surplus;
 
 	foreach my $v (@{ $c->{Votes} }) {
+	    my $previously = $v->{TransferredSurplus};
+	    push @$previously, $c->{Cand};
+
 	    my $A = $surplus * $v->{Weight};
 	    my $F = 100000;
-	    my $xfervalue = floor(($A * $F) / $B) / $F;
+	    my $xfervalue = ((($A * $F) / $B) -> bfloor() ) / $F;
 	    # SLGEO 48(3): we do arithmetic to 5 d3ecimal places,
 	    # but always rounding down
 	    votelog $v, "transferring with value $xfervalue (A=$A B=$B)";
 	    $v->{Weight} = $xfervalue;
+
+	    if (defined $tspr{"@$previously"}) {
+		die unless $tspr{"@$previously"} == $xfervalue;
+	    } else {
+		$tspr{"@$previously"} = $xfervalue;
+		prf "transfer value of ballots %s: %10s\n",
+		    "@$previously", $xfervalue;
+	    }
 	    sortballots $v;
 	}
 	$c->{Votes} = { }; # will crash if we access it again