File Coverage

blib/lib/Graph/Maker/Keller.pm

Criterion	Covered	Total	%
statement	6	8	75.0
branch			n/a
condition			n/a
subroutine	3	3	100.0
pod			n/a
total	9	11	81.8

# Copyright 2015, 2016, 2017 Kevin Ryde
#
# This file is part of Graph-Maker-Other.
#
# This file is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 3, or (at your option) any later
# version.
#
# This file is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.
#
# You should have received a copy of the GNU General Public License along
# with Graph-Maker-Other.  See the file COPYING.  If not, see
# .

package Graph::Maker::Keller;
use 5.004;
use strict;
use Graph::Maker;

use vars '$VERSION','@ISA';
$VERSION = 8;
@ISA = ('Graph::Maker');


sub _default_graph_maker {
  require Graph;
  Graph->new(@_);
}

sub _is_edge {
  my ($from,$to) = @_;
  my $diff = $from ^ $to;
  my $seen_two = 0;
  my $seen_any = 0;
  while ($diff) {
    my $digit = $diff & 3;
    if ($digit)      { $seen_any++; }
    if ($digit == 2) { $seen_two++; }
    if ($seen_any >= 2 && $seen_two) {
      return 1;
    }
    $diff >>= 2;
  }
  return 0;
}

sub init {
  my ($self, %params) = @_;

  my $N        = delete($params{'N'}) || 0;
  my $subgraph = delete($params{'subgraph'}) || 0;
  my $graph_maker = delete($params{'graph_maker'}) || \&_default_graph_maker;

  my $graph = $graph_maker->(%params);

  my $directed = $graph->is_directed;

  if ($subgraph) {
    $graph->set_graph_attribute (name => "Keller Subgraph $N");

    my @vertices;
    foreach my $to (1 .. (1 << (2*$N))-1) {
      if (_is_edge(0,$to)) {
        $graph->add_vertex($to);
        push @vertices, $to;
      }
    }
    foreach my $i (0 .. $#vertices) {
      my $from = $vertices[$i];
      foreach my $j ($i+1 .. $#vertices) {
        my $to = $vertices[$j];
        if (_is_edge($from,$to)) {
          if ($directed) { $graph->add_edge($to, $from); }
          $graph->add_edge($from, $to);
        }
      }
    }

  } else {
    $graph->set_graph_attribute (name => "Keller $N");

    my $max_vertex = (1 << (2*$N)) - 1;
    for my $from (0 .. $max_vertex) {
      $graph->add_vertex($from);  # for $N < 2 where there are no edges

      for my $to ($from+1 .. $max_vertex) {
        if (_is_edge($from,$to)) {
          $graph->add_edge($from, $to);
          if ($directed) { $graph->add_edge($to, $from); }
        }
      }
    }
  }
  return $graph;
}

Graph::Maker->add_factory_type('Keller' => __PACKAGE__);
1;





    # for (my($i,$imask) = (0,1);
    #      $i < $N;
    #      $i++, $imask <<= 2) {
    #   foreach my $ixor ($imask, 2*$imask, 3*$imask) {
    #     my $in = $n ^ $ixor;
    #
    #     for (my($j,$jmask) = (0,2);
    #          $j < $N;
    #          $j++, $jmask <<= 2) {
    #       next if $i == $j;
    #
    #       my $n2 = $in ^ $jmask;
    #       if ($directed || $n2 > $n) {
    #         $graph->add_edge($n, $n2);
    #       }
    #     }
    #   }
    # }


__END__