remove no-tiebreak configuration flag - ACR tiebreaking no longer opt…

…ional

src/perl/prefvote/README.md

@@ -219,9 +219,8 @@ It only makes sense for tie-breaking, where becomes meaningful if everything els
     For high-stakes elections, a runoff may be a more appropriate action.
     For polls on approval of a proposal or measure, a tie should mean failure to achieve a majority.
 
-    _PrefVote::Core_ makes average choice rank (ACR) data available to subclasses which must use it for tie-breaking,
-    except when the _no-tiebreak_ configuration flag is set.
-    Ties should be extremely unlikely with ACR tie-breaking enabled.
+    _PrefVote::Core_ makes average choice rank (ACR) data available to subclasses which must use it for tie-breaking.
+    Ties are less likely due to ACR tie-breaking, but cannot be made impossible.
 
 - result\_yaml()
 

src/perl/prefvote/bin/vote-count

@@ -266,14 +266,6 @@ Supported configuration settings:
 
 =over 1
 
-=item no-tiebreak
-
-takes a boolean value, 1 for true or 0 for false.
-This indicating PrefVote voting methods should disable the
-normal tie-breaking by Average Choice Rank (ACR).
-The default is false, which allows tie-breaking with ACR.
-This setting is used by the STV, Schulze and RankedPairs voting methods.
-
 =item input-ties
 
 (for use in testing only)

src/perl/prefvote/lib/PrefVote/Config.pm

@@ -68,12 +68,6 @@ All configuration entries default to non-existent and undefined.
 
 =over 1
 
-=item no-tiebreak
-
-If defined, this contains a boolean flag that inhibits the PrefVote system's use of L<PrefVote::Core>
-"average choice rank" (ACR) data for tie-breaking. This is recognized by L<PrefVote::STV>, L<PrefVote::Schulze> and
-L<PrefVote::RankedPairs>.
-
 =item input-ties
 
 (experimental)

src/perl/prefvote/lib/PrefVote/Core.pm

@@ -1103,9 +1103,8 @@ For low-stakes polls, such as where to meet for dinner, a random selection such
 For high-stakes elections, a runoff may be a more appropriate action.
 For polls on approval of a proposal or measure, a tie should mean failure to achieve a majority.
 
-I<PrefVote::Core> makes average choice rank (ACR) data available to subclasses which must use it for tie-breaking,
-except when the I<no-tiebreak> configuration flag is set.
-Ties should be extremely unlikely with ACR tie-breaking enabled.
+I<PrefVote::Core> makes average choice rank (ACR) data available to subclasses which must use it for tie-breaking.
+Ties are less likely with ACR tie-breaking, but cannot be made impossible.
 
 =item result_yaml()
 

src/perl/rankedpairs/lib/PrefVote/RankedPairs.pm

@@ -408,13 +408,10 @@ sub cmp_choice
     }
 
     # 2nd comparison: choice/candidate's average ballot placement in ascending order
-    my $tiebreak_disabled = $self->config("no-tiebreak") // 0;    # config flag to disable tie-breaking by avg rank
-    if ( not $tiebreak_disabled ) {
-        my $place1 = $self->average_ranking($cand1);
-        my $place2 = $self->average_ranking($cand2);
-        if ( not fp_equal( $place1, $place2 ) ) {
-            return fp_cmp( $place1, $place2 );
-        }
+    my $place1 = $self->average_ranking($cand1);
+    my $place2 = $self->average_ranking($cand2);
+    if ( not fp_equal( $place1, $place2 ) ) {
+        return fp_cmp( $place1, $place2 );
     }
 
     return 0;

src/perl/schulze/lib/PrefVote/Schulze/Round.pm

@@ -630,10 +630,6 @@ sub narrow_winners
     my $self        = shift;
     my $schulze_ref = shift;    # ref to PrefVote::Schulze object
 
-    # skip step if configuration flag disables PrefVotes's tie-breaking by average rank to strictly follow algorithm
-    my $tiebreak_disabled = $self->config("no-tiebreak") // 0;    # config flag to disable tie-breaking by avg rank
-    return if $tiebreak_disabled;
-
     # sort winners by average ballot placement order
     my @winning_group =
         sort { fp_cmp( $schulze_ref->average_ranking($a), $schulze_ref->average_ranking($b) ) } $self->win_flag_keys();

src/perl/stv/lib/PrefVote/STV.pm

@@ -270,14 +270,12 @@ sub process_winners
     # quota exceeded - we have a winner!
     my @round_winner;
     my $place             = $self->winners_count() + 1;
-    my $tiebreak_disabled = $self->config("no-tiebreak") // 0;    # config flag to disable tie-breaking by avg rank
     foreach my $curr_key (@round_candidate) {
 
         # mark all the candidates over quota who are tied for first place as winners
         if (
             ( $round->tally_get($curr_key)->votes() == $round->tally_get( $round_candidate[0] )->votes() )
-            and ( $tiebreak_disabled
-                or fp_equal( $self->average_ranking($curr_key), $self->average_ranking( $round_candidate[0] ) ) )
+            and fp_equal( $self->average_ranking($curr_key), $self->average_ranking( $round_candidate[0] ) )
             )
         {
             my $c_votes        = $round->tally_get($curr_key)->votes();
@@ -316,13 +314,11 @@ sub eliminate_losers
 
     # mark candidates tied for last as eliminated
     my @round_eliminated;
-    my $tiebreak_disabled = $self->config("no-tiebreak") // 0;    # config flag to disable tie-breaking by avg rank
     for ( $i = ( scalar @round_candidate ) - 1 ; $i > 0 ; $i-- ) {
         my $indexed_cand = $round_candidate[$i];
         if (
             ( $round->tally_get($last_cand)->votes() == $round->tally_get($indexed_cand)->votes() )
-            and ( $tiebreak_disabled
-                or fp_equal( $self->average_ranking($last_cand), $self->average_ranking($indexed_cand) ) )
+            and fp_equal( $self->average_ranking($last_cand), $self->average_ranking($indexed_cand) )
             )
         {
             $round->tally_get($indexed_cand)->mark_as_eliminated();
@@ -370,7 +366,6 @@ sub count
         }
 
         # sort in descending order
-        my $tiebreak_disabled = $self->config("no-tiebreak") // 0;    # config flag to disable tie-breaking by avg rank
         my @round_candidate   = $round->sort_candidates(
             sub {
                 # 1st/primary comparison: votes for candidate in descending order
@@ -381,12 +376,10 @@ sub count
                 }
 
                 # 2nd comparison: average ballot-ranking position in ascending order
-                if ( not $tiebreak_disabled ) {
-                    my $acr0 = $self->average_ranking( $_[0] );
-                    my $acr1 = $self->average_ranking( $_[1] );
-                    if ( not fp_equal( $acr0, $acr1 ) ) {
-                        return fp_cmp( $acr0, $acr1 );
-                    }
+                my $acr0 = $self->average_ranking( $_[0] );
+                my $acr1 = $self->average_ranking( $_[1] );
+                if ( not fp_equal( $acr0, $acr1 ) ) {
+                    return fp_cmp( $acr0, $acr1 );
                 }
 
                 # 3rd comparison: alphabetical (so ties in testing keep consistent order)