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lib/Algorithm/Evolutionary/Op/Permutation.pm  view on Meta::CPAN

use strict;
use warnings;

=head1 NAME

Algorithm::Evolutionary::Op::Permutation - Per-mutation. Got it? 

=head1 SYNOPSIS

  use Algorithm::Evolutionary::Op::Permutation;

  my $op = new Algorithm::Evolutionary::Op::Permutation ; #Create from scratch
  my $bit_chromosome =  new Algorithm::Evolutionary::Individual::BitString 10;
  $op->apply( $bit_chromosome );

  my $priority = 2;
  my $max_iterations = 100; # Less than 10!, absolute maximum number
			    # of permutations
  $op = new Algorithm::Evolutionary::Op::Permutation $priority, $max_iterations;

  my $xmlStr=<<EOC;
  <op name='Permutation' type='unary' rate='2' />
  EOC
  my $ref = XMLin($xmlStr);

  my $op = Algorithm::Evolutionary::Op::->fromXML( $ref );
  print $op->asXML(), "\n*Arity ->", $op->arity(), "\n";

=head1 Base Class

L<Algorithm::Evolutionary::Op::Base>

=head1 DESCRIPTION

Class independent permutation operator; any individual that has the
    C<_str> instance variable (like
    L<Algorithm::Evolutionary::Individual::String> and
    L<Algorithm::Evolutionary::Individual::BitString>)  will have some
    of its elements swapped. Each string of length l has l!
    permutations; the C<max_iterations> parameter should not be higher
    than that. 

This kind of operator is used extensively in combinatorial
    optimization problems. See, for instance, 
  @article{prins2004simple,
   title={{A simple and effective evolutionary algorithm for the vehicle routing problem}},
   author={Prins, C.},
   journal={Computers \& Operations Research},
   volume={31},
   number={12},
   pages={1985--2002},
   issn={0305-0548},
   year={2004},
   publisher={Elsevier}
  }

And, of course, L<Algorithm::MasterMind>, where it is used in the
    evolutionary algorithms solutions. 


=cut

package  Algorithm::Evolutionary::Op::Permutation;

use lib qw( ../../.. );

our ($VERSION) = ( '$Revision: 3.7 $ ' =~ /(\d+\.\d+)/ );

use Carp;
use Clone qw(clone);
use List::Util qw(shuffle); 

use base 'Algorithm::Evolutionary::Op::Base';

#Class-wide constants
our $APPLIESTO =  'Algorithm::Evolutionary::Individual::String';
our $ARITY = 1;

=head1 METHODS

=head2 new( [$rate = 1][, $max_iterations = 10] )

Creates a new permutation operator; see 
    L<Algorithm::Evolutionary::Op::Base> for details common to all
    operators. The chromosome will undergo a random number of at most
    C<$max_iterations>. By default, it equals 10. 

=cut

sub new {
  my $class = shift;
  my $rate = shift || 1;

  my $self = Algorithm::Evolutionary::Op::Base::new( 'Algorithm::Evolutionary::Op::Permutation', $rate );
  return $self;
}


=head2 create