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use strict; # -*- cperl -*-
use warnings;
use lib qw( ../../../../lib );
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=head1 NAME
Algorithm::Evolutionary::Fitness::Rastrigin - Implementation of Rastrigin's function
=head1 SYNOPSIS
    my $n_dimensions=2;  #Max. number of elements to choose
    my $rastrigin = Algorithm::Evolutionary::Fitness::Rastrigin->new( $n_dimensions ); 
=head1 DESCRIPTION
Classical Rastrigin function, used for tests of numerical optimization problems. 
Check it at L<http://www-optima.amp.i.kyoto-u.ac.jp/member/student/hedar/Hedar_files/TestGO_files/Page2607.htm>
=head1 METHODS
=cut
package Algorithm::Evolutionary::Fitness::Rastrigin;
our ($VERSION) = ( '$Revision: 3.3 $ ' =~ / (\d+\.\d+)/ ) ;
use Carp qw( croak );
use base qw(Algorithm::Evolutionary::Fitness::Base);
use constant PI2    => 8 * atan2(1, 1);
use constant RASTRIGIN_A => 10;
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=head2 new
Creates a new instance of the problem, with the said number of bits and peaks
=cut 
sub new {
  my $class = shift;
  my ( $n_dimensions ) = @_;
  #Instantiate superclass
  my $self = $class->SUPER::new();
  #Assign stuff
  $self->{'n_dimensions'} = $n_dimensions;
  $self->{'_base_fitness'} = RASTRIGIN_A*$n_dimensions;
  $self->initialize();
  return $self;
}
sub _really_apply {
    my $self = shift;
    return $self->Rastrigin( @_ );
}
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=head2 Rastrigin
Applies the knapsack problem to the string, using a penalty function
=cut
sub Rastrigin {
    my $self = shift;
    my @array = @_;
    my $fitness = $self->{'_base_fitness'};
    for ( my $i = 0; $i < $self->{'n_dimensions'}; $i ++ ) {
      $fitness += $array[$i]*$array[$i]- RASTRIGIN_A *cos(PI2*$array[$i]);
    }
    return $fitness;
}
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=head1 Copyright
   
  This file is released under the GPL. See the LICENSE file included in this distribution,
  or go to http://www.fsf.org/licenses/gpl.txt
  CVS Info: $Date: 2010/09/28 19:41:26 $ 
  $Header: /media/Backup/Repos/opeal/opeal/Algorithm-Evolutionary/lib/Algorithm/Evolutionary/Fitness/Rastrigin.pm,v 3.3 2010/09/28 19:41:26 jmerelo Exp $ 
  $Author: jmerelo $ 
  $Revision: 3.3 $
  $Name $
=cut
"Pi squared???";