X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=blobdiff_plain;f=parse;h=13fe2f23395fabb16bb0a9b15d3bc6496f9454ea;hp=e176ecc250713bf4e03b34a4ab3f6007f93dc64d;hb=454c5cdcf27ce0ac28aa9f62585387139690c779;hpb=5dc538aedf489281785ce32f25dcaa18385ac6a5

diff --git a/parse b/parse
index e176ecc..13fe2f2 100755
--- a/parse
+++ b/parse
@@ -1,13 +1,14 @@
 #!/usr/bin/perl -w
 use strict;
 use utf8;
+use autodie;
 
 use Data::Printer;
 use Graph::Directed;
 
-binmode STDIN, 'encoding(UTF-8)' or die;
-binmode STDOUT, 'encoding(UTF-8)' or die;
-binmode STDERR, 'encoding(UTF-8)' or die;
+binmode STDIN, 'encoding(UTF-8)';
+binmode STDOUT, 'encoding(UTF-8)';
+binmode STDERR, 'encoding(UTF-8)';
 
 our @choices;
 our %choices;
@@ -26,6 +27,7 @@ while (<>) {
     s/\s+$//;
     next if m/^\s*\#/;
     next unless m/\S/;
+    next if m/^\s/;
     if (m/^([A-Z]+)\s*\=\s*(\S.*)$/) {
 	my ($choname, $desc) = ($1,$2);
 	my $cho = addchoice($choname, Desc => $desc);
@@ -56,6 +58,8 @@ our @vab;
 
 # Go through the voters and construct V(A,B)
 
+print "\nPreference matrix\n";
+
 foreach my $iv (@invotes) {
     my ($votestr,$voter) = @$iv;
     eval {
@@ -90,29 +94,29 @@ foreach my $iy (-2..$#ch) {
     foreach my $ix (-2..$#ch) {
 	if ($iy==-1) {
 	    if ($ix==-1) {
-		printf "+" or die;
+		printf "+";
 	    } else {
-		printf "------" or die;
+		printf "------";
 	    }
 	} elsif ($ix==-1) {
-	    printf "|" or die;
+	    printf "|";
 	} elsif ($ix==-2 && $iy==-2) {
-	    printf "V(Y,X)" or die;
+	    printf "V(Y,X)";
 	} elsif ($iy==-2) {
-	    printf "%5s ", $choices[$ix] or die $!;
+	    printf "%5s ", $choices[$ix];
 	} elsif ($ix==-2) {
-	    printf "%5s ", $choices[$iy] or die $!;
+	    printf "%5s ", $choices[$iy];
 	} else {
 	    my $v = \( $vab[$iy][$ix] );
 	    $$v ||= [ ];
 	    if (@$$v) {
-		printf "%5d ", (scalar @$$v) or die $!;
+		printf "%5d ", (scalar @$$v);
 	    } else {
-		printf "%5s ", "" or die $!;
+		printf "%5s ", "";
 	    }
 	}
     }
-    printf "\n" or die $!;
+    printf "\n";
 }
 
 sub drop ($$) {
@@ -121,7 +125,7 @@ sub drop ($$) {
     $ch[$i]{Dropped} = $why;
 }
 
-print "# quorum A.6(2)\n" or die $!;
+print "\nQuorum A.6(2) (quorum is $quorum)\n";
 
 foreach my $i (0..$#choices) {
     next if $ch[$i]{Dropped};
@@ -131,7 +135,7 @@ foreach my $i (0..$#choices) {
     drop $i, "quorum ($v < $quorum)";
 }
 
-print "# maj. ratio A.6(3)\n" or die $!;
+print "\nMajority ratio A.6(3)\n";
 
 foreach my $i (0..$#choices) {
     next if $ch[$i]{Dropped};
@@ -144,56 +148,119 @@ foreach my $i (0..$#choices) {
     drop $i, "majority ratio ($vad * $majr->[1] <= $vda * $majr->[0])";
 }
 
-my $defeats = Graph::Directed->new; # A.6(4)
+print "\nDefeats A.6(4)\n";
+
+my $defeats = Graph::Directed->new;
+
+sub chremain () {
+    return grep { !$ch[$_]{Dropped} } (0..$#ch);
+}
 
-foreach my $ia (0..$#ch) {
-    foreach my $ib (0..$#ch) {
-	my $vab = $vab[$ia][$ib];
-	my $vba = $vab[$ib][$ia];
+foreach my $ia (chremain()) {
+    $defeats->add_vertex($choices[$ia]);
+    foreach my $ib (chremain()) {
+	my $vab = scalar @{ $vab[$ia][$ib] };
+	my $vba = scalar @{ $vab[$ib][$ia] };
 	next unless $vab > $vba;
-	print "defeat: $choices[$ia] beats $choices[$ib] ($vab > $vba)\n"
-	    or die $!;
-	$defeats->add_vertex($ia,$ib);
+	my $diff = $vab - $vba;
+	print "defeat: $choices[$ia] beats $choices[$ib]",
+	    " ($vab > $vba: $diff)\n";
+	$defeats->add_edge($choices[$ia],$choices[$ib]);
     }
 }
 
-print "# transitive closure A.6(5)\n" or die $!;
+sub chvab ($$) {
+    my ($ca,$cb) = @_;
+    my $v = $vab[ $choices{$ca}{Index} ][ $choices{$cb}{Index} ];
+    return scalar @$v;
+}
+
+sub weaker ($$) {
+    # A.6(7)(1)
+    my ($def1,$def2) = @_;
+    my ($ca,$cx) = @$def1;
+    my ($cb,$cy) = @$def1;
+    return 1 if chvab($ca, $cx) < chvab($cb, $cy);
+    return 1 if chvab($ca, $cx) == chvab($cb, $cy)
+	&& chvab($cx, $ca) > chvab($cy, $cb);
+    return 0;
+}
 
-my $tdefeats = $defeats->transitive_closure();
+our $schwartz;
 
-print "# schwartz set A.6(6)\n" or die $!;
+for (;;) {
+    # loop from A6(5)
 
-my $schwartz = $defeats->copy();
+    print "defeats graph: $defeats\n";
 
-foreach my $ia (0..$#ch) {
-    foreach my $ib (0..$#ch) {
-	next if $tdefeats->has_edge($ia,$b);
-	next if !$tdefeats->has_edge($b,$ia);
-	print "not in Schwartz set: $choices[$ia] because $choices[$ib]\n"
-	    or die $!;
-	$schwartz->delete_vertex($ia);
-	last;
+    print "\nTransitive closure A.6(5)\n";
+
+    my $tdefeats = $defeats->transitive_closure();
+
+    print "closure graph: $tdefeats\n";
+
+    print "\nSchwartz set A.6(6)\n";
+    
+    $schwartz = $defeats->copy();
+
+    foreach my $ia (chremain()) {
+	foreach my $ib (chremain()) {
+	    next if $tdefeats->has_edge($choices[$ia],$choices[$ib]);
+	    next if !$tdefeats->has_edge($choices[$ib],$choices[$ia]);
+	    print "not in Schwartz set: $choices[$ia] because $choices[$ib]\n";
+	    $schwartz->delete_vertex($choices[$ia]);
+	    last;
+	}
     }
-}
 
-print "# dropping weakest defeats A.6(7)\n" or die $!;
+    print "\nDropping weakest defeats A.6(7)\n";
 
-my @weakest = ();
+    our @weakest = ();
 
-foreach my $edge (@{ $schwartz->edges() }) {
-    if (!@weakest) {
-	# no weakest edges yet
-    } elsif (weaker($edge, $weakest[0])) {
-	# this edge is weaker than previous weakest, start new set
-	@weakest = ();
-    } elsif (weaker($weakest[0], $edge)) {
-	# weakest edge is weaker than this one, ignore this one
-	next;
-    } else {
-	# weakest edge is exactly as weak as this one, add this one
+    foreach my $edge ($schwartz->edges()) {
+#	print " considering @$edge\n";
+	if (!@weakest) {
+	    # no weakest edges yet
+	} elsif (weaker($edge, $weakest[0])) {
+	    # this edge is weaker than previous weakest, start new set
+	    @weakest = ();
+	} elsif (weaker($weakest[0], $edge)) {
+	    # weakest edge is weaker than this one, ignore this one
+	    next;
+	} else {
+	    # weakest edge is exactly as weak as this one, add this one
+	}
+	push @weakest, $edge;
+    }
+
+    last unless @weakest;
+
+    my $w = $weakest[0];
+    printf "weakest defeats %d > %d\n", 
+        chvab($w->[0], $w->[1]),
+	chvab($w->[1], $w->[0]);
+    foreach my $weakest (@weakest) {
+	my ($ca,$cb) = @$weakest;
+	print "weakest defeat $ca > $cb\n";
+	$defeats->delete_edge($ca,$cb);
     }
-    push @weakest, $edge;
+
+    print "defeats within the Schwartz set, round again\n";
+}
+
+print "no defeats within the Schwartz set\n";
+print "final schwartz set:\n\n";
+
+if ($schwartz->vertices() == 1) {
+    print "WINNER IS:\n";
+} else {
+    print "WINNER IS ONE OF (CASTING VOTE DECIDES):\n";
 }
 
+printf "    %-5s %s\n", $_, $choices{$_}{Desc}
+    foreach ($schwartz->vertices());
+
+print ".\n";
+
 #p %choices;
 #p @vab;