# NAME

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

# 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";
```

# Base Class

Algorithm::Evolutionary::Op::Base

# DESCRIPTION

Class independent permutation operator; any individual that has the `_str`

instance variable (like Algorithm::Evolutionary::Individual::String and Algorithm::Evolutionary::Individual::BitString) will have some of its elements swapped. Each string of length l has l! permutations; the `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, Algorithm::MasterMind, where it is used in the evolutionary algorithms solutions.

# METHODS

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

Creates a new permutation operator; see Algorithm::Evolutionary::Op::Base for details common to all operators. The chromosome will undergo a random number of at most `$max_iterations`

. By default, it equals 10.

## create

Creates a new mutation operator with an application priority, which defaults to 1.

Called create to distinguish from the classwide ctor, new. It just makes simpler to create an Operator

## apply( $chromosome )

Applies at most `max_iterations`

permutations to a "Chromosome" that includes the `_str`

instance variable. The number of iterations will be random, so that applications of the operator on the same individual will create diverse offspring.

## SEE ALSO

Uses Algorithm::Permute, which is purported to be the fastest permutation library around. Might change it in the future to Algorithm::Combinatorics, which is much more comprehensive.

# 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: 2013/01/09 07:22:50 $
$Header: /media/Backup/Repos/opeal/opeal/Algorithm-Evolutionary/lib/Algorithm/Evolutionary/Op/Permutation.pm,v 3.7 2013/01/09 07:22:50 jmerelo Exp $
$Author: jmerelo $
$Revision: 3.7 $
```