COPYING: provide a licence

[appendix-a6.git] / compute-scottish-stv

diff --git a/compute-scottish-stv b/compute-scottish-stv
index e09f1ebcefb4430d7b8299afa0c27b8dcbd4d3e5..98ec3082bd92de269a79af720f4ba8472c8f163a 100755 (executable)
--- a/compute-scottish-stv
+++ b/compute-scottish-stv
@@ -31,6 +31,7 @@ our %cands;
 our $stage=0;
 our $quota;
 our %tie;
+our @elected;
 
 our $DIGS = 5;
 our $F = (new Math::BigRat 10)->bpow($DIGS);
@@ -57,6 +58,8 @@ $SIG{__DIE__} = sub {
     die $_[0];
 };
 
+sub total_history_cmp ();
+
 sub unkopt ($$) {
     my ($what,$opt) = @_;
     if ($opt =~ m/^[A-Z]/) {
@@ -66,6 +69,23 @@ sub unkopt ($$) {
     }
 }
 
+my $display_cmp = \&total_history_cmp;
+my $for_compare = 0;
+
+while (@ARGV && $ARGV[0] =~ m/^\-/) {
+    $_ = shift @ARGV;
+    if (m/^--$/) {
+       last;
+    } elsif (m/^--sort=alpha$/) {
+       $display_cmp = sub { $b->{Cand} cmp $a->{Cand} };
+    } elsif (m/^--for-compare$/) {
+       $for_compare = 1;
+       unshift @ARGV, '--sort=alpha';
+    } else {
+       die;
+    }
+}
+
 for (;;) {
     $_ = <>;
     if (m/^\| /) {
@@ -185,20 +205,31 @@ sub sv ($) {
 
 sub prf {
     my $fmt = shift;
-    printf "stage %d: ".$fmt, $stage, @_;
+    printf " ".$fmt, @_;
+}
+sub prfm {
+    prf @_ unless $for_compare;
 }
 
 sub countballots () {
+    my @pr;
+
     foreach my $c (values %cands) {
        next if $c->{NonCont};
        $c->{Total} = 0/1;
        $c->{Total} += $_->{Weight} foreach @{ $c->{Votes} };
        print DEBUG "counted $c->{Cand} $c->{Total}\n";
        $c->{History}[$stage-1] = $c->{Total};
+       push @pr, $c;
+    }
+
+    if ($for_compare) {
+       # for comparison with OpenSTV, which always prints
+       # the quota for every elected candidate
+       push @pr, { %$_, Total => $quota } foreach @elected;
     }
 
-    foreach my $c (reverse sort total_history_cmp
-                  grep { !$_->{NonCont} } values %cands) {
+    foreach my $c (reverse sort $display_cmp @pr) {
        prf "candidate %-10s: %s votes\n", $c->{Cand}, sv $c->{Total};
     }
 }
@@ -206,8 +237,9 @@ sub countballots () {
 sub computequota () {
     my $totalvalid = 0/1;
     $totalvalid += $_->{Total} foreach values %cands;
-    $quota = floor($totalvalid / (1 + $seats));
-    prf "quota %s\n", sv $quota;
+    $quota = floor($totalvalid / (1 + $seats) + 1);
+    prfm "total valid %s\n", sv $totalvalid;
+    prf  "quota       %s\n", sv $quota;
 }
 
 sub total_history_cmp () {
@@ -278,7 +310,7 @@ sub select_best_worst ($$$$) {
            $selectcand, "@all";
     } else {
        $selectcand = $maybe[0]{Cand};
-       prf "$what %s\n", $selectcand;
+       prfm "$what %s\n", $selectcand;
     }
 
     return $cands{$selectcand};
@@ -286,24 +318,31 @@ sub select_best_worst ($$$$) {
 
 sub elect_core ($) {
     my ($c) = @_;
-    prf "*** ELECT %s \`%s' ***\n", $c->{Cand}, $c->{Desc};
+    prfm "*** ELECT %s \`%s' ***\n", $c->{Cand}, $c->{Desc};
     $c->{NonCont} = 'Elected';
+    push @elected, $c;
 }
 
 $stage = 0;
 
 for (;;) {
     $stage++;
+    printf "stage %3d:\n", $stage;
 
     sortballots @allvotes if $stage == 1;
 
-    my $seats_remain = $seats
-       - grep { ($_->{NonCont} // '') eq 'Elected' } values %cands;
+    my $seats_remain = $seats - @elected;
+
+    prfm "seats remaining %d\n", $seats_remain;
+
+    last unless $seats_remain;
+
     if (continuing() <= $seats_remain) {
        foreach my $c (continuing()) {
            prf "electing %s to fill remaining place(s)\n", $c->{Cand};
            elect_core $c;
        }
+       countballots() if $for_compare;
        last;
     }
 
@@ -328,6 +367,8 @@ for (;;) {
            next;
        }
 
+       last if $seats_remain == 1; # don't bother doing more transfers
+
        my $B = $c->{Total};
        my %tspr;
 
@@ -348,7 +389,7 @@ for (;;) {
                die unless $tspr{"@$previously"} == $xfervalue;
            } else {
                $tspr{"@$previously"} = $xfervalue;
-               prf "transfer value of ballots %s: %s\n",
+               prfm "transfer value of ballots %20s: %s\n",
                    "@$previously", sv $xfervalue;
            }
        }
@@ -365,7 +406,7 @@ for (;;) {
        -1, 'eliminating';
 
     if ($c) {
-       prf "=== eliminating %s \`%s' ===\n", $c->{Cand}, $c->{Desc};
+       prfm "=== eliminating %s \`%s' ===\n", $c->{Cand}, $c->{Desc};
        $c->{NonCont} = 'Eliminated';
 
        sortballots @{ $c->{Votes} };
@@ -375,4 +416,17 @@ for (;;) {
     die;
 }
 
-print "done.\n"; 
+print "Winners:\n"; 
+
+if ($for_compare) {
+    foreach my $c (sort { $a->{Cand} cmp $b->{Cand} } @elected) {
+       printf "  %s\n", $c->{Cand};
+    }
+} else {
+    foreach my $i (0..$#elected) {
+       my $c = $elected[$i];
+       printf " %3d. %-10s %s\n", $i+1, $c->{Cand}, $c->{Desc};
+    }
+}
+
+print "done.\n";