```
use strict; # -*- cperl -*-
use warnings;
use lib qw( ../../../../lib );
=head1 NAME
Algorithm::Evolutionary::Fitness::ECC - Error Correcting codes problem generator
=head1 SYNOPSIS
my $number_of_codewords = 10;
my $min_distance = 1;
my $p_peaks = Algorithm::Evolutionary::Fitness::ECC->new( $number_of_codewords, $min_distance );
=head1 DESCRIPTION
Extracted from article "Effects of scale-free and small-world topologies on binary coded self-adaptive CEA", by Giacobini et al [Ga]. Quoting:
" The ECC problem was presented in
[MW]. We will consider a three-tuple (n, M, d), where n is the length of each codeword
(number of bits), M is the number of codewords, and d is the minimum Hamming
distance between any pair of codewords. Our objective will be to find a code which
has a value for d as large as possible (reflecting greater tolerance to noise and errors),
given previously fixed values for n and M . The problem we have studied is a simplified
version of that in [MW]. In our case we search half of the codewords (M/2) that will
compose the code, and the other half is made up by the complement of the codewords
computed by the algorithm"
[Ga] Mario Giacobini, Mike Preuss, Marco Tomassini: Effects of Scale-Free and Small-World Topologies on Binary Coded Self-adaptive CEA. EvoCOP 2006: 86-98.
[MW] F. J. MacWilliams and N. J. A. Sloane. The Theory of Error-Correcting Codes. North-
Holland, Amsterdam, 1977.
=head1 METHODS
=cut
package Algorithm::Evolutionary::Fitness::ECC;
our ($VERSION) = ( '$Revision: 3.2 $ ' =~ / (\d+\.\d+)/ ) ;
use Carp qw(croak);
use lib qw(../../.. ../.. ..);
use base qw(Algorithm::Evolutionary::Fitness::String);
use Algorithm::Evolutionary::Utils qw(hamming);
=head2 new
Creates a new instance of the problem, with the said number of bits and peaks
=cut
sub new {
my $class = shift;
my ($number_of_codewords, $min_distance ) = @_;
croak "Too few codewords" if !$number_of_codewords;
croak "Distance too small" if !$min_distance;
my $self = $class->SUPER::new();
bless $self, $class;
$self->initialize();
$self->{'number_of_codewords'} = $number_of_codewords;
return $self;
}
=head2 _really_apply
Applies the instantiated problem to a chromosome
=cut
sub _really_apply {
my $self = shift;
return $self->ecc( @_ );
}
=head2 ecc
Applies the instantiated problem to a string
=cut
sub ecc {
my $self = shift;
my $string = shift || croak "Can't work with a null string";
my $cache = $self->{'_cache'};
if ( $cache->{$string} ) {
return $cache->{$string};
}
my $length = length($string)/$self->{'number_of_codewords'};
my @codewords = ( $string =~ /.{$length}/gs );
my $distance;
for ( my $i = 0; $i <= $#codewords; $i ++ ) {
for ( my $j = $i+1; $j <= $#codewords; $j ++ ) {
my $this_distance = hamming( $codewords[$i], $codewords[$j] );
$distance += 1/(1+$this_distance*$this_distance);
}
}
$cache->{$string} = 1/$distance;
return $cache->{$string};
}
=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: 2009/07/24 10:25:49 $
$Header: /media/Backup/Repos/opeal/opeal/Algorithm-Evolutionary/lib/Algorithm/Evolutionary/Fitness/ECC.pm,v 3.2 2009/07/24 10:25:49 jmerelo Exp $
$Author: jmerelo $
$Revision: 3.2 $
$Name $
=cut
"What???";
```