org.apache.commons.math3.genetics

Class CycleCrossover<T>

java.lang.Object

org.apache.commons.math3.genetics.CycleCrossover<T>

Type Parameters:

T - generic type of the AbstractListChromosomes for crossover

All Implemented Interfaces:

CrossoverPolicy

public class CycleCrossover<T>
extends java.lang.Object
implements CrossoverPolicy

Cycle Crossover [CX] builds offspring from ordered chromosomes by identifying cycles between two parent chromosomes. To form the children, the cycles are copied from the respective parents.

To form a cycle the following procedure is applied:

1. start with the first gene of parent 1
2. look at the gene at the same position of parent 2
3. go to the position with the same gene in parent 1
4. add this gene index to the cycle
5. repeat the steps 2-5 until we arrive at the starting gene of this cycle

The indices that form a cycle are then used to form the children in alternating order, i.e. in cycle 1, the genes of parent 1 are copied to child 1, while in cycle 2 the genes of parent 1 are copied to child 2, and so forth ...

Example (zero-start cycle):

 p1 = (8 4 7 3 6 2 5 1 9 0)    X   c1 = (8 1 2 3 4 5 6 7 9 0)
 p2 = (0 1 2 3 4 5 6 7 8 9)    X   c2 = (0 4 7 3 6 2 5 1 8 9)

 cycle 1: 8 0 9
 cycle 2: 4 1 7 2 5 6
 cycle 3: 3
 

This policy works only on AbstractListChromosome, and therefore it is parameterized by T. Moreover, the chromosomes must have same lengths.

Since:

3.1

See Also:

Cycle Crossover Operator

Constructor Summary

Constructors

Constructor and Description
CycleCrossover() Creates a new CycleCrossover policy.
CycleCrossover(boolean randomStart) Creates a new CycleCrossover policy using the given randomStart behavior.

Method Summary

Modifier and Type	Method and Description
ChromosomePair	crossover(Chromosome first, Chromosome second) Perform a crossover operation on the given chromosomes.
boolean	isRandomStart() Returns whether the starting index is chosen randomly or set to zero.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CycleCrossover

public CycleCrossover()

Creates a new CycleCrossover policy.

CycleCrossover

public CycleCrossover(boolean randomStart)

Creates a new CycleCrossover policy using the given randomStart behavior.

Parameters:

randomStart - whether the start index shall be chosen randomly or be set to 0

Method Detail

isRandomStart

public boolean isRandomStart()

Returns whether the starting index is chosen randomly or set to zero.

Returns:

true if the starting index is chosen randomly, false otherwise

crossover

public ChromosomePair crossover(Chromosome first,
                                Chromosome second)
                         throws DimensionMismatchException,
                                MathIllegalArgumentException

Perform a crossover operation on the given chromosomes.

Specified by:

crossover in interface CrossoverPolicy

Parameters:

first - the first chromosome.

second - the second chromosome.

Returns:

the pair of new chromosomes that resulted from the crossover.

Throws:

MathIllegalArgumentException - if the chromosomes are not an instance of AbstractListChromosome

DimensionMismatchException - if the length of the two chromosomes is different