X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=appendix-a6.git;a=blobdiff_plain;f=compute-scottish-stv;h=81dc6adeafb10d553c50b2153a250a530bfc8966;hp=575f10ed4f5275812acc8dcf3493f0f5b3326653;hb=5b395082d4e913cd3049505065af086380c0016c;hpb=4cd1697174e964f23d0ad06faaa2bcd24288d174 diff --git a/compute-scottish-stv b/compute-scottish-stv index 575f10e..81dc6ad 100755 --- a/compute-scottish-stv +++ b/compute-scottish-stv @@ -31,19 +31,35 @@ our %cands; our $stage=0; our $quota; our %tie; +our @elected; + +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 total_history_cmp (); + sub unkopt ($$) { my ($what,$opt) = @_; if ($opt =~ m/^[A-Z]/) { @@ -53,6 +69,19 @@ sub unkopt ($$) { } } +my $display_cmp = \&total_history_cmp; + +while (@ARGV && $ARGV[0] =~ m/^\-/) { + $_ = shift @ARGV; + if (m/^--$/) { + last; + } elsif (m/^--sort=alpha$/) { + $display_cmp = sub { $b->{Cand} cmp $a->{Cand} }; + } else { + die; + } +} + for (;;) { $_ = <>; if (m/^\| /) { @@ -98,6 +127,7 @@ 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 +141,7 @@ 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 +175,69 @@ 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 $display_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) + 1); + prf "total valid %s quota %s\n", (sv $totalvalid), (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 +266,14 @@ 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})) { @@ -242,6 +304,7 @@ sub elect_core ($) { my ($c) = @_; prf "*** ELECT %s \`%s' ***\n", $c->{Cand}, $c->{Desc}; $c->{NonCont} = 'Elected'; + push @elected, $c; } $stage = 0; @@ -251,8 +314,12 @@ for (;;) { sortballots @allvotes if $stage == 1; - my $seats_remain = $seats - - grep { ($_->{NonCont} // '') eq 'Elected' } values %cands; + my $seats_remain = $seats - @elected; + + prf "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}; @@ -277,23 +344,24 @@ for (;;) { # SLGEO 48 my $surplus = $c->{Total} - $quota; - if ($surplus <= 0) { + if ($surplus <= 0/1) { prf "no surplus\n"; next; } + last if $seats_remain == 1; # don't bother doing more transfers + 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 +371,12 @@ for (;;) { die unless $tspr{"@$previously"} == $xfervalue; } else { $tspr{"@$previously"} = $xfervalue; - prf "transfer value of ballots %s: %10s\n", - "@$previously", $xfervalue; + prf "transfer value of ballots %20s: %s\n", + "@$previously", sv $xfervalue; } - sortballots $v; } + sortballots @{ $c->{Votes} }; + $c->{Votes} = { }; # will crash if we access it again next; } @@ -319,12 +388,21 @@ for (;;) { -1, 'eliminating'; if ($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; } die; } -print "done.\n"; +print "Winners:\n"; + +foreach my $i (0..$#elected) { + my $c = $elected[$i]; + printf " %3d. %-10s %s\n", $i+1, $c->{Cand}, $c->{Desc}; +} + +print "done.\n";