CycleCrossover (Apache Commons Math 3.6.1 API)

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 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

Methods
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.
`protected ChromosomePair`	`mate(AbstractListChromosome<T> first, AbstractListChromosome<T> second)` Helper for `crossover(Chromosome, Chromosome)`.

Methods inherited from class java.lang.Object
clone, equals, finalize, 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
  - mate
```
protected ChromosomePair mate(AbstractListChromosome<T> first,
                  AbstractListChromosome<T> second)
                       throws DimensionMismatchException
```
    Helper for crossover(Chromosome, Chromosome). Performs the actual crossover.
    
    Parameters:
    first - the first chromosome
    second - the second chromosome
    
    Returns:
    the pair of new chromosomes that resulted from the crossover
    
    Throws:
    
    DimensionMismatchException - if the length of the two chromosomes is different

Class CycleCrossover<T>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

CycleCrossover

CycleCrossover

Method Detail

isRandomStart

crossover

mate