Perl x Open Food Facts Hackathon: Paris, France - May 24-25 Learn more

JMERELO / Algorithm-Evolutionary-0.56 / lib / Algorithm / Evolutionary / Op / NoChangeTerm.pm 

            

              
1
2
—
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
—
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
—
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
—
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98

              
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: 1.1.1.1 $ ' =~ /(\d+\.\d+)/ ) ;
use Algorithm::Evolutionary::Op::Base;
our @ISA = qw(Algorithm::Evolutionary::Op::Base);
# Class-wide constants
our $APPLIESTO =  'ARRAY';
our $ARITY = 1;
=head2 new
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 $self;
}
=head2 apply
Checks if the first member of the population has the same fitness as before,
and increments counter. The population I<should be ordered>
=cut
sub apply ($) {
  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 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: 2008/02/12 17:49:39 $ 
  $Header: /cvsroot/opeal/Algorithm-Evolutionary/lib/Algorithm/Evolutionary/Op/NoChangeTerm.pm,v 1.1.1.1 2008/02/12 17:49:39 jmerelo Exp $ 
  $Author: jmerelo $ 
  $Revision: 1.1.1.1 $
  $Name $
  
=cut
"The truth is out there";