From 2eaee49e874572d17f6682d10abc737f00c38e1c Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 2 Feb 2014 20:40:14 +0000
Subject: [PATCH] seems to work

---
 parse | 36 +++++++++++++++++++++++-------------
 1 file changed, 23 insertions(+), 13 deletions(-)

diff --git a/parse b/parse
index c04d33b..adb3d7d 100755
--- a/parse
+++ b/parse
@@ -147,10 +147,15 @@ foreach my $i (0..$#choices) {
 
 my $defeats = Graph::Directed->new; # A.6(4)
 
-foreach my $ia (0..$#ch) {
-    foreach my $ib (0..$#ch) {
-	my $vab = $vab[$ia][$ib];
-	my $vba = $vab[$ib][$ia];
+sub chremain () {
+    return grep { !$ch[$_]{Dropped} } (0..$#ch);
+}
+
+foreach my $ia (chremain()) {
+    $defeats->add_vertex($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";
 	$defeats->add_vertex($ia,$ib);
@@ -168,6 +173,8 @@ sub weaker ($$) {
     return 0;
 }
 
+print "defeats graph: $defeats\n";
+
 our $schwartz;
 
 for (;;) {
@@ -177,14 +184,16 @@ for (;;) {
 
     my $tdefeats = $defeats->transitive_closure();
 
-    print "# schwartz set A.6(6)\n";
+    print "closure graph: $tdefeats\n";
+
+    print "# Schwartz set A.6(6)\n";
     
     $schwartz = $defeats->copy();
 
-    foreach my $ia (0..$#ch) {
-	foreach my $ib (0..$#ch) {
-	    next if $tdefeats->has_edge($ia,$b);
-	    next if !$tdefeats->has_edge($b,$ia);
+    foreach my $ia (chremain()) {
+	foreach my $ib (chremain()) {
+	    next if $tdefeats->has_edge($ia,$ib);
+	    next if !$tdefeats->has_edge($ib,$ia);
 	    print "not in Schwartz set: $choices[$ia] because $choices[$ib]\n";
 	    $schwartz->delete_vertex($ia);
 	    last;
@@ -195,7 +204,7 @@ for (;;) {
 
     our @weakest = ();
 
-    foreach my $edge (@{ $schwartz->edges() }) {
+    foreach my $edge ($schwartz->edges()) {
 	if (!@weakest) {
 	    # no weakest edges yet
 	} elsif (weaker($edge, $weakest[0])) {
@@ -213,8 +222,8 @@ for (;;) {
     last unless @weakest;
     
     printf "weakest defeats %d > %d", 
-	(scalar @{ $vab[$_->[0]][$_->[1]]) },
-	(scalar @{ $vab[$_->[1]][$_->[0]]) };
+	(scalar @{ $vab[$_->[0]][$_->[1]] }),
+	(scalar @{ $vab[$_->[1]][$_->[0]] });
     foreach my $weakest (@weakest) {
 	my ($ia,$ib) = @$weakest;
 	print "weakest defeat $choices[$ia] > $choices[$ib]\n";
@@ -227,7 +236,8 @@ for (;;) {
 print "# no defeats within the Schwartz set\n";
 print "FINAL SCHWARTZ SET:\n";
 
-print $choices[$_] foreach (@{ $schwartz->nodes() });
+printf "    %-5s %s\n", $choices[$_], $ch[$_]{Desc}
+    foreach ($schwartz->vertices());
 
 print ".\n";
 
-- 
2.30.2