org.moeaframework.core
Class NondominatedSortingPopulation

java.lang.Object
  org.moeaframework.core.Population
      org.moeaframework.core.NondominatedSortingPopulation

All Implemented Interfaces:

Iterable<Solution>

Direct Known Subclasses:

ReferencePointNondominatedSortingPopulation

public class NondominatedSortingPopulation
extends Population

Population that maintains the rank and crowdingDistance attributes for its solutions by invoking FastNondominatedSorting.evaluate(Population). This population tracks modifications and performs fast non-dominated sorting only when required. Only changes made to this population can be tracked; changes made directly to the contained solutions will not be detected. Therefore, it may be necessary to invoke update() manually.

The iterator() method returned by Population must use the size(), get(int) and remove(int) methods to ensure proper functionality.

Constructor Summary

NondominatedSortingPopulation()
Constructs an empty population that maintains the rank and crowdingDistance attributes for its solutions.

NondominatedSortingPopulation(DominanceComparator comparator)
Constructs an empty population that maintains the rank and crowdingDistance attributes for its solutions.

NondominatedSortingPopulation(DominanceComparator comparator, Iterable<? extends Solution> iterable)
Constructs a population initialized with the specified solutions that maintains the rank and crowdingDistance attributes for its solutions.

NondominatedSortingPopulation(Iterable<? extends Solution> iterable)
Constructs a population initialized with the specified solutions that maintains the rank and crowdingDistance attributes for its solutions.

Method Summary

boolean	add(Solution solution) Adds the specified solution to this population.
void	clear() Removes all solutions from this population.
Solution	get(int index) Returns the solution at the specified index in this population.
Iterator<Solution>	iterator() Returns an iterator for accessing the solutions in this population.
void	prune(int size) Prunes the population to the specified size.
void	remove(int index) Removes the solution at the specified index from this population.
boolean	remove(Solution solution) Removes the specified solution from this population, if present.
void	sort(Comparator<? super Solution> comparator) Sorts the solutions in this population using the specified comparator.
void	truncate(int size) Equivalent to calling truncate(size, new NondominatedSortingComparator()).
void	truncate(int size, Comparator<? super Solution> comparator) Sorts this population using the specified comparator and removes the last (maximum) solutions until this population's size is within the specified size.
void	update() Updates the rank and crowding distance of all solutions in this population.

Methods inherited from class org.moeaframework.core.Population

addAll, addAll, contains, containsAll, containsAll, indexOf, isEmpty, removeAll, removeAll, size

Methods inherited from class java.lang.Object

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

Constructor Detail

NondominatedSortingPopulation

public NondominatedSortingPopulation()

Constructs an empty population that maintains the rank and crowdingDistance attributes for its solutions.

NondominatedSortingPopulation

public NondominatedSortingPopulation(DominanceComparator comparator)

Constructs an empty population that maintains the rank and crowdingDistance attributes for its solutions.

Parameters:

comparator - the dominance comparator

NondominatedSortingPopulation

public NondominatedSortingPopulation(DominanceComparator comparator,
                                     Iterable<? extends Solution> iterable)

Constructs a population initialized with the specified solutions that maintains the rank and crowdingDistance attributes for its solutions.

Parameters:

comparator - the dominance comparator

iterable - the solutions used to initialize this population

NondominatedSortingPopulation

public NondominatedSortingPopulation(Iterable<? extends Solution> iterable)

Constructs a population initialized with the specified solutions that maintains the rank and crowdingDistance attributes for its solutions.

Parameters:

iterable - the solutions used to initialize this population

Method Detail

add

public boolean add(Solution solution)

Description copied from class: Population

Adds the specified solution to this population.

Overrides:

add in class Population

Parameters:

solution - the solution to be added

Returns:

true if the population was modified as a result of this method; false otherwise.

get

public Solution get(int index)

Description copied from class: Population

Returns the solution at the specified index in this population.

Overrides:

get in class Population

Parameters:

index - the index of the solution to be returned

Returns:

the solution at the specified index

remove

public void remove(int index)

Description copied from class: Population

Removes the solution at the specified index from this population.

Overrides:

remove in class Population

Parameters:

index - the index of the solution to be removed

remove

public boolean remove(Solution solution)

Description copied from class: Population

Removes the specified solution from this population, if present.

Overrides:

remove in class Population

Parameters:

solution - the solution to be removed

Returns:

true if this population was modified as a result of this method; false otherwise

clear

public void clear()

Description copied from class: Population

Removes all solutions from this population.

Overrides:

clear in class Population

iterator

public Iterator<Solution> iterator()

Description copied from class: Population

Returns an iterator for accessing the solutions in this population.

Specified by:

iterator in interface Iterable<Solution>

Overrides:

iterator in class Population

Returns:

an Iterator.

sort

public void sort(Comparator<? super Solution> comparator)

Description copied from class: Population

Sorts the solutions in this population using the specified comparator. Invocations of certain methods on this population may alter the ordering of solutions, so the get, remove and iteration methods should be called immediately after invoking this method.

Overrides:

sort in class Population

Parameters:

comparator - the comparator to be used for sorting

truncate

public void truncate(int size,
                     Comparator<? super Solution> comparator)

Description copied from class: Population

Sorts this population using the specified comparator and removes the last (maximum) solutions until this population's size is within the specified size.

Overrides:

truncate in class Population

Parameters:

size - the target population size after truncation

comparator - the comparator to be used for truncation

truncate

public void truncate(int size)

Equivalent to calling truncate(size, new NondominatedSortingComparator()).

Parameters:

size - the target population size after truncation

prune

public void prune(int size)

Prunes the population to the specified size. This is similar to truncate(int), except the crowding distance is recalculated each time a solution is removed.

Parameters:

size - the target population size after pruning

update

public void update()

Updates the rank and crowding distance of all solutions in this population. This method will in general be called automatically when the population is modified. However, only changes made to this population can be tracked; changes made directly to the contained solutions will not be detected. Therefore, it may be necessary to invoke update() manually.