Crowding

java.lang.Object
- org.opt4j.optimizer.ea.Crowding

All Implemented Interfaces:

FrontDensityIndicator
```
public class Crowding
extends Object
implements FrontDensityIndicator
```
The Crowding calculates the crowding distance of Individuals as used for instance in the the Nsga2 algorithm. A bounding box around each individual is defined and restricted by the neighboring individuals in each dimension. The crowding distance is the sum of the side-lengths of the bounding box. If an individual does not have neighbors on all sides, the crowding distance is maximal. A normalization in each dimension is applied.

See Also:

"A fast and elitist multiobjective genetic algorithm : NSGA-II, K. Deb, A. Pratap, S. Agarwal, and T. Meyarivan Evolutionary Computation, IEEETransactions on, vol. 6, no. 2, pp. 182-197, August 2002."

Constructor Summary

Constructors
Constructor Description

Crowding()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Map<Individual,Double>`	`getDensityValues(Collection<Individual> individuals)`	Returns the density values for a collection on `Individuals`.
`List<Individual>`	`order(Map<Individual,Double> values)`	Returns an ordered list of the `Individual`s corresponding to their crowding distance.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Crowding
```
public Crowding()
```
- Method Detail
  - order
```
public List<Individual> order(Map<Individual,Double> values)
```
    Returns an ordered list of the Individuals corresponding to their crowding distance. Individuals with a high crowding distance are sorted to the front.
    
    Parameters:
    
    values - the map of individuals to their crowding distance values
    
    Returns:
    
    the sorted list of individuals based on their crowding distance
  - getDensityValues
```
public Map<Individual,Double> getDensityValues(Collection<Individual> individuals)
```
    Description copied from interface: FrontDensityIndicator
    
    Returns the density values for a collection on Individuals.
    
    Specified by:
    
    getDensityValues in interface FrontDensityIndicator
    
    Parameters:
    
    individuals - the individuals
    
    Returns:
    
    a map of each individual to its density value