X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=blobdiff_plain;f=compute-scottish-stv;h=e09f1ebcefb4430d7b8299afa0c27b8dcbd4d3e5;hp=575f10ed4f5275812acc8dcf3493f0f5b3326653;hb=4642960b13763e24dcb10ab40cd650e12e1f84fe;hpb=4cd1697174e964f23d0ad06faaa2bcd24288d174

diff --git a/compute-scottish-stv b/compute-scottish-stv
index 575f10e..e09f1eb 100755
--- a/compute-scottish-stv
+++ b/compute-scottish-stv
@@ -32,18 +32,31 @@ our $stage=0;
 our $quota;
 our %tie;
 
+our $DIGS = 5;
+our $F = (new Math::BigRat 10)->bpow($DIGS);
+
 open DEBUG, ">.compute.log" or die $!;
 DEBUG->autoflush(1);
 
-$SIG{__WARN__} = sub {
+sub debug_dump () {
     print DEBUG Dumper(\%tie,
 		       \@non_transferable,
 		       \%cands,
 		       \@allvotes,
 		       $stage, $quota);
+}
+
+$SIG{__WARN__} = sub {
+    $SIG{__DIE__} = undef;
+    debug_dump;
     confess $_[0];
 };
 
+$SIG{__DIE__} = sub {
+    debug_dump;
+    die $_[0];
+};
+
 sub unkopt ($$) {
     my ($what,$opt) = @_;
     if ($opt =~ m/^[A-Z]/) {
@@ -98,6 +111,7 @@ for (;;) {
 $cands{$_}{Cand} = $_ foreach keys %cands;
 $_->{Weight} //= 1/1 foreach @allvotes;
 $_->{TransferredSurplus} //= [ ] foreach @allvotes;
+$_->{OrigPrefs} //= [ @{ $_->{Prefs} } ] foreach @allvotes;
 
 sub votelog ($$) {
     my ($vote,$m) = @_;
@@ -111,6 +125,7 @@ sub sortballots (@) {
     # Strips that first preference from the ballot.
     # If the first preference has been eliminated, strips it
     # and looks for further preferences.
+    print DEBUG "sortballots ".(scalar @_)."...\n";
     foreach my $v (@_) {
 	my $firstprefs = shift @{ $v->{Prefs} };
 	my $w = $v->{Weight};
@@ -144,39 +159,69 @@ sub sortballots (@) {
     }
 }
 
+sub floor ($) {
+    my ($v) = @_;
+    $v = new Math::BigRat $v; # we need a copy
+    return $v->bfloor();
+}
+
+sub sv ($) {
+    my ($in) = @_;
+    my $v = new Math::BigRat $in; # just in case
+    my $intpart = floor($v);
+    my $frac = $v - $intpart;
+    my $good = floor($frac * $F);
+    my $bad = $frac * $F - $good;
+    my $s = sprintf "%7d", $intpart;
+    if ($frac) {
+	$s .= sprintf ".%0${DIGS}d", $good;
+	$s .= sprintf "%-4s", ($bad ? "+$bad" : "");
+    } else {
+	$s .= sprintf " %${DIGS}s%4s", '', '';
+    }
+#print STDERR "# $in => $s # (intpart=$intpart frac=$frac)\n";
+    return $s;
+}
+
 sub prf {
     my $fmt = shift;
     printf "stage %d: ".$fmt, $stage, @_;
 }
 
 sub countballots () {
-    foreach my $cand (sort keys %cands) {
-	my $c = $cands{$cand};
+    foreach my $c (values %cands) {
 	next if $c->{NonCont};
-	$c->{Total} = 0;
+	$c->{Total} = 0/1;
 	$c->{Total} += $_->{Weight} foreach @{ $c->{Votes} };
-	prf "candidate %-10s: %10s votes\n", $cand, $c->{Total};
+	print DEBUG "counted $c->{Cand} $c->{Total}\n";
 	$c->{History}[$stage-1] = $c->{Total};
     }
+
+    foreach my $c (reverse sort total_history_cmp
+		   grep { !$_->{NonCont} } values %cands) {
+	prf "candidate %-10s: %s votes\n", $c->{Cand}, sv $c->{Total};
+    }
 }
 
 sub computequota () {
-    my $totalvalid = 0;
+    my $totalvalid = 0/1;
     $totalvalid += $_->{Total} foreach values %cands;
-    $quota = ($totalvalid / (1 + $seats)) -> bfloor();
-    prf "quota %10s\n", $quota;
+    $quota = floor($totalvalid / (1 + $seats));
+    prf "quota %s\n", sv $quota;
 }
 
 sub total_history_cmp () {
     my $ha = $a->{History};
     my $hb = $b->{History};
+    my $m = "stage $stage history cmp $a->{Cand} $b->{Cand}";
+    print DEBUG  "$m...\n";
     foreach my $s (reverse 0 .. $stage-1) {
 	my $d = $ha->[$s] <=> $hb->[$s];
 	next unless $d;
-	print DEBUG "history cmp $a->{Cand} $b->{Cand}".
-	    " => $d (#$s $ha->[$s] $hb->[$s])\n";
+	print DEBUG "$m => $d (#$s $ha->[$s] $hb->[$s])\n";
 	return $d;
     }
+    print DEBUG "$m => 0\n";
     return 0;
 }
 
@@ -205,13 +250,14 @@ sub select_best_worst ($$$$) {
 
     for (;;) {
 	my $nextc = $maybe[$nequal];
+	last unless $nextc;
 
 	# Only interested in those who compare equal according to the
 	# history (SLGEO 49(2)); NB our history includes the current
 	# round.
 	
 	last if $signum*($a = $maybe[0], $b = $nextc, total_history_cmp) > 0;
-	$nextc++;
+	$nequal++;
     }
 
     if ($nequal > 1 && !$wanttiebreak->($maybe[0]{Total})) {
@@ -277,7 +323,7 @@ for (;;) {
 	# SLGEO 48
 	my $surplus = $c->{Total} - $quota;
 
-	if ($surplus <= 0) {
+	if ($surplus <= 0/1) {
 	    prf "no surplus\n";
 	    next;
 	}
@@ -285,15 +331,14 @@ for (;;) {
 	my $B = $c->{Total};
 	my %tspr;
 
-	prf "surplus %10s\n", $surplus;
+	prf "surplus %s\n", sv $surplus;
 
 	foreach my $v (@{ $c->{Votes} }) {
 	    my $previously = $v->{TransferredSurplus};
 	    push @$previously, $c->{Cand};
 
 	    my $A = $surplus * $v->{Weight};
-	    my $F = 100000;
-	    my $xfervalue = ((($A * $F) / $B) -> bfloor() ) / $F;
+	    my $xfervalue = floor(($A * $F) / $B) / $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)";
@@ -303,11 +348,12 @@ for (;;) {
 		die unless $tspr{"@$previously"} == $xfervalue;
 	    } else {
 		$tspr{"@$previously"} = $xfervalue;
-		prf "transfer value of ballots %s: %10s\n",
-		    "@$previously", $xfervalue;
+		prf "transfer value of ballots %s: %s\n",
+		    "@$previously", sv $xfervalue;
 	    }
-	    sortballots $v;
 	}
+	sortballots @{ $c->{Votes} };
+
 	$c->{Votes} = { }; # will crash if we access it again
 	next;
     }
@@ -319,8 +365,10 @@ for (;;) {
 	-1, 'eliminating';
 
     if ($c) {
-	prf "=== eliminating %s (%s) ===\n", $c->{Cand}, $c->{Desc};
+	prf "=== eliminating %s \`%s' ===\n", $c->{Cand}, $c->{Desc};
 	$c->{NonCont} = 'Eliminated';
+
+	sortballots @{ $c->{Votes} };
 	next;
     }