```
use strict;
use warnings;
=head1 NAME
Algorithm::Evolutionary::Op::NoChangeTerm - Checks for termination of an algorithm; terminates
when several generations transcur without change
=head1 SYNOPSIS
my $nct = new Algorithm::Evolutionary::Op::NoChangeTerm 10;
#nct->apply( \@pop ) will return false after 10 generations w/o change
=head1 Base Class
L<Algorithm::Evolutionary::Op::Base|Algorithm::Evolutionary::Op::Base>
=head1 DESCRIPTION
Algorithm::Evolutionary::Op::NoChangeTerm is used when we want an
algorithm to finish when the population has stagnated, or the global
optimum is found. It counts how many generations the population has
not changed, and returns false after that limit is reached.
It is useful if you want to run an algorithm for a certain time, or if
you want to apply some fancy diversity operator
=head1 METHODS
=cut
package Algorithm::Evolutionary::Op::NoChangeTerm;
our ($VERSION) = ( '$Revision: 3.0 $ ' =~ / (\d+\.\d+)/ ) ;
use base 'Algorithm::Evolutionary::Op::Base';
=head2 new( [$number_of_generations_without_change] )
Creates a new terminator. Takes as an argument the number of
generations after which it will return false, which defaults to 10.
=cut
sub new {
my $class = shift;
my $hash = { noChangeCounterMax => shift || 10,
noChangeCounter => 0,
lastBestFitness => rand()}; # A random value, unlikely
# to be matched
my $self = Algorithm::Evolutionary::Op::Base::new( __PACKAGE__, 1, $hash );
return $self;
}
=head2 apply( $population )
Checks if the first member of the population has the same fitness as before,
and increments counter. The population I<should be ordered>
=cut
sub apply ($) {
my $self = shift;
my $pop = shift;
if ( $pop->[0]->Fitness() == $self->{_lastBestFitness} ) {
$self->{_noChangeCounter}++;
# print "NCT => ", $self->{_noChangeCounter}++, "\n";
} else {
$self->{_lastBestFitness}= $pop->[0]->Fitness();
$self->{_noChangeCounter} = 0;
}
return $self->{_noChangeCounter} < $self->{_noChangeCounterMax};
}
=head1 See Also
L<Algorithm::Evolutionary::Op::FullAlgorithm> needs an object of this class to check
for the termination condition. It's normally used alongside "generation-type"
objects such as L<Algorithm::Evolutionary::Op::Easy>.
There are other options for termination conditions: L<Algorithm::Evolutionary::Op::DeltaTerm> and
L<Algorithm::Evolutionary::Op::GenerationalTerm>.
=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 08:46:59 $
$Header: /media/Backup/Repos/opeal/opeal/Algorithm-Evolutionary/lib/Algorithm/Evolutionary/Op/NoChangeTerm.pm,v 3.0 2009/07/24 08:46:59 jmerelo Exp $
$Author: jmerelo $
$Revision: 3.0 $
$Name $
=cut
"The truth is out there";
```