Package org.moeaframework.core.population

Class Population

java.lang.Object
org.moeaframework.core.population.Population
All Implemented Interfaces:
Iterable<Solution>, Copyable<Population>, Stateful, Displayable, Formattable<Solution>
Direct Known Subclasses:
MSOPSRankedPopulation, NondominatedPopulation, NondominatedSortingPopulation, ReferenceVectorGuidedPopulation
public class Population extends Object implements Iterable<Solution>, Formattable<Solution>, Copyable<Population>, Stateful
A collection of solutions and common methods for manipulating the collection.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Population()
    Constructs an empty population.
    Population(Iterable<? extends Solution> iterable)
    Constructs a population initialized with a collection of solutions.
    Population(T[] solutions)
    Constructs a population initialized with an array of solutions.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(Solution solution)
    Adds the specified solution to this population.
    boolean
    addAll(Iterable<? extends Solution> iterable)
    Adds a collection of solutions to this population.
    <T extends Solution>
    boolean
    addAll(T[] solutions)
    Adds an array of solutions to this population.
    List<Solution>
    asList()
    Returns the contents of this population as a list.
    TabularData<Solution>
    asTabularData()
    Returns the contents of this object as a TabularData instance, which can be used to save, print, or format the data in various ways.
    void
    clear()
    Removes all solutions from this population.
    boolean
    contains(Solution solution)
    Returns true if this population contains the specified solution; false otherwise.
    boolean
    containsAll(Iterable<? extends Solution> iterable)
    Returns true if this population contains all the solutions in the specified collection; false otherwise.
    <T extends Solution>
    boolean
    containsAll(T[] solutions)
    Returns true if this population contains all the solutions in the specified array; false otherwise.
    Population
    copy()
    Returns a copy of this population.
    Population
    filter(Predicate<? super Solution> predicate)
    Returns a new population containing only the solutions matching the given predicate.
    Solution
    get(int index)
    Returns the solution at the specified index in this population.
    double[]
    getLowerBounds()
    Computes the lower bounds of this population.
    double[]
    getUpperBounds()
    Computes the upper bounds of this population.
    int
    indexOf(Solution solution)
    Returns the index of the specified solution in this population.
    boolean
    isEmpty()
    Returns true if this population contains no solutions; false otherwise.
    Iterator<Solution>
    iterator()
    Returns an iterator for accessing the solutions in this population.
    static Population
    load(File file)
    Loads a population from the specified result file.
    static Population
    load(Reader reader)
    Loads a population from the specified reader.
    void
    loadState(ObjectInputStream stream)
    Loads the state of this object from the stream.
    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.
    boolean
    removeAll(Iterable<? extends Solution> iterable)
    Removes all solutions in the specified collection from this population.
    boolean
    removeAll(Predicate<? super Solution> predicate)
    Removes all solutions matching the given predicate.
    <T extends Solution>
    boolean
    removeAll(T[] solutions)
    Removes all solutions in the specified array from this population.
    void
    replace(int index, Solution solution)
    Replaces the solution at the given index.
    void
    save(File file)
    Saves all solutions to the specified result file.
    void
    save(Writer writer)
    Saves all solutions to the specified result file.
    void
    saveState(ObjectOutputStream stream)
    Writes the state of this object to the stream.
    int
    size()
    Returns the number of solutions in this population.
    void
    sort(Comparator<? super Solution> comparator)
    Sorts the solutions in this population using the specified comparator.
    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.

    Methods inherited from class java.lang.Object

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

    Methods inherited from interface org.moeaframework.util.format.Displayable

    display

    Methods inherited from interface org.moeaframework.util.format.Formattable

    display, display, display, save, save, save

    Methods inherited from interface java.lang.Iterable

    forEach, spliterator

  • Constructor Details

    • Population

      public Population()
      Constructs an empty population.

    • Population

      public Population(Iterable<? extends Solution> iterable)
      Constructs a population initialized with a collection of solutions.
      Parameters:
      iterable - the collection of solutions for initializing this population

    • Population

      public Population(T[] solutions)
      Constructs a population initialized with an array of solutions.
      Type Parameters:
      T - the type of solutions in the array
      Parameters:
      solutions - the array of solutions for initializing this population

  • Method Details

    • get

      public Solution get(int index)
      Returns the solution at the specified index in this population.
      Parameters:
      index - the index of the solution to be returned
      Returns:
      the solution at the specified index
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0) || (index >= size())

    • remove

      public void remove(int index)
      Removes the solution at the specified index from this population.
      Parameters:
      index - the index of the solution to be removed
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0) || (index >= size())

    • indexOf

      public int indexOf(Solution solution)
      Returns the index of the specified solution in this population. Invocations of certain methods on this population may alter the ordering of solutions, so the index returned should be used immediately by the get or remove methods.
      Parameters:
      solution - the solution whose index is to be returned
      Returns:
      the index of the specified solution

    • add

      public boolean add(Solution solution)
      Adds the specified solution to this population.
      Parameters:
      solution - the solution to be added
      Returns:
      true if the population was modified as a result of this method; false otherwise.

    • addAll

      public boolean addAll(Iterable<? extends Solution> iterable)
      Adds a collection of solutions to this population.
      Parameters:
      iterable - the collection of solutions to be added
      Returns:
      true if the population was modified as a result of this method; false otherwise

    • addAll

      public <T extends Solution> boolean addAll(T[] solutions)
      Adds an array of solutions to this population.
      Type Parameters:
      T - the type of solutions in the array
      Parameters:
      solutions - the solutions to be added
      Returns:
      true if the population was modified as a result of this method; false otherwise

    • replace

      public void replace(int index, Solution solution)
      Replaces the solution at the given index.
      Parameters:
      index - the index to replace
      solution - the new solution

    • clear

      public void clear()
      Removes all solutions from this population.

    • contains

      public boolean contains(Solution solution)
      Returns true if this population contains the specified solution; false otherwise.
      Parameters:
      solution - the solution whose presence is tested
      Returns:
      true if this population contains the specified solution; false otherwise

    • containsAll

      public boolean containsAll(Iterable<? extends Solution> iterable)
      Returns true if this population contains all the solutions in the specified collection; false otherwise.
      Parameters:
      iterable - the collection whose presence is tested
      Returns:
      true if this population contains all the solutions in the specified collection; false otherwise

    • containsAll

      public <T extends Solution> boolean containsAll(T[] solutions)
      Returns true if this population contains all the solutions in the specified array; false otherwise.
      Type Parameters:
      T - the type of solutions in the array
      Parameters:
      solutions - the array whose presence is tested
      Returns:
      true if this population contains all the solutions in the specified array; false otherwise

    • isEmpty

      public boolean isEmpty()
      Returns true if this population contains no solutions; false otherwise.
      Returns:
      true if this population contains no solutions; false otherwise.

    • iterator

      public Iterator<Solution> iterator()
      Returns an iterator for accessing the solutions in this population.
      Specified by:
      iterator in interface Iterable<Solution>

    • remove

      public boolean remove(Solution solution)
      Removes the specified solution from this population, if present.
      Parameters:
      solution - the solution to be removed
      Returns:
      true if this population was modified as a result of this method; false otherwise

    • removeAll

      public boolean removeAll(Iterable<? extends Solution> iterable)
      Removes all solutions in the specified collection from this population.
      Parameters:
      iterable - the collection of solutions to be removed
      Returns:
      true if this population was modified as a result of this method; false otherwise

    • removeAll

      public <T extends Solution> boolean removeAll(T[] solutions)
      Removes all solutions in the specified array from this population.
      Type Parameters:
      T - the type of solutions in the array
      Parameters:
      solutions - the array of solutions to be removed
      Returns:
      true if this population was modified as a result of this method; false otherwise

    • removeAll

      public boolean removeAll(Predicate<? super Solution> predicate)
      Removes all solutions matching the given predicate.
      Parameters:
      predicate - the filter that returns true on solutions to remove
      Returns:
      true if this population was modified as a result of this method; false otherwise

    • filter

      public Population filter(Predicate<? super Solution> predicate)
      Returns a new population containing only the solutions matching the given predicate.

      The filtered population should be treated as a "view" into this population. The structure of the filtered population can be modified without affecting this population (e.g., by adding, removing, or sorting), but any modifications to the solutions contained in either will appear in both. Use copy() to create an independent copy.

      Parameters:
      predicate - the filter that returns true on solutions to keep in the filtered population
      Returns:
      the filtered population

    • size

      public int size()
      Returns the number of solutions in this population.
      Returns:
      the number of solutions in this population

    • sort

      public void sort(Comparator<? super Solution> comparator)
      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.
      Parameters:
      comparator - the comparator to be used for sorting

    • getLowerBounds

      public double[] getLowerBounds()
      Computes the lower bounds of this population. Since all objectives are minimized, this is equivalent to the ideal point. Also note that all solutions, including those violating constraints, are included.
      Returns:
      the lower bounds

    • getUpperBounds

      public double[] getUpperBounds()
      Computes the upper bounds of this population. Since all objectives are minimized, this is equivalent to the Nadir point. Also note that all solutions, including those violating constraints, are included.
      Returns:
      the upper bounds

    • truncate

      public 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.
      Parameters:
      size - the target population size after truncation
      comparator - the comparator to be used for truncation

    • copy

      public Population copy()
      Returns a copy of this population. This can be thought of as a "deep copy", which creates a copy of both the population itself and copies of the individual solutions in the population. Consequently, the returned copy is completely independent, such that any modifications to the contents or order will not impact the original.

      Since creating such a "deep copy" can be expensive, prefer using the constructor Population(Iterable) or addAll(Iterable) whenever possible. These alternatives are useful when filtering or reordering the solutions, but the solutions themselves are left unchanged.

      Specified by:
      copy in interface Copyable<Population>
      Returns:
      the copy of this population

    • asList

      public List<Solution> asList()
      Returns the contents of this population as a list. Consider using copy() first if planning to modify the solutions in any way.
      Returns:
      the contents of this population as a list

    • asTabularData

      public TabularData<Solution> asTabularData()
      Description copied from interface: Formattable
      Returns the contents of this object as a TabularData instance, which can be used to save, print, or format the data in various ways.
      Specified by:
      asTabularData in interface Formattable<Solution>
      Returns:
      the TabularData instance

    • save

      public void save(File file) throws IOException
      Saves all solutions to the specified result file. Files created using this method should only be loaded using the load(File) method.
      Parameters:
      file - the file to which the solutions are written
      Throws:
      IOException - if an I/O error occurred

    • save

      public void save(Writer writer) throws IOException
      Saves all solutions to the specified result file. Files created using this method should only be loaded using the load(File) method.
      Parameters:
      writer - the writer to which the solutions are written
      Throws:
      IOException - if an I/O error occurred

    • load

      public static Population load(File file) throws IOException
      Loads a population from the specified result file. If the file contains multiple population entries, only the last is returned. Files read using this method should only have been created using save(File).
      Parameters:
      file - the file
      Returns:
      the population
      Throws:
      EmptyResultFileException - if the result file was empty or not properly formatted
      IOException - if an I/O error occurred

    • load

      public static Population load(Reader reader) throws IOException
      Loads a population from the specified reader. If the reader contains multiple population entries, only the last is returned. This method does not close the reader!
      Parameters:
      reader - the reader
      Returns:
      the population
      Throws:
      EmptyResultFileException - if the result file was empty or not properly formatted
      IOException - if an I/O error occurred

    • saveState

      public void saveState(ObjectOutputStream stream) throws IOException
      Description copied from interface: Stateful
      Writes the state of this object to the stream. The order that objects are written to the stream is important. We recommend first calling super.saveState(stream) followed by writing each field.
      Specified by:
      saveState in interface Stateful
      Parameters:
      stream - the stream
      Throws:
      IOException - if an I/O error occurred

    • loadState

      public void loadState(ObjectInputStream stream) throws IOException, ClassNotFoundException
      Description copied from interface: Stateful
      Loads the state of this object from the stream. The order for reading objects from the stream must match the order they are written to the stream in Stateful.saveState(ObjectOutputStream).
      Specified by:
      loadState in interface Stateful
      Parameters:
      stream - the stream
      Throws:
      IOException - if an I/O error occurred
      ClassNotFoundException - if the stream referenced a class that is not defined