MOEA Framework 2.12
API Specification

org.moeaframework.algorithm
Class MSOPSRankedPopulation

java.lang.Object
  extended by org.moeaframework.core.Population
      extended by org.moeaframework.algorithm.MSOPSRankedPopulation
All Implemented Interfaces:
Iterable<Solution>

public class MSOPSRankedPopulation
extends Population

Population implementing the ranking scheme used by the Multiple Single Objective Pareto Sampling (MSOPS) algorithm. Solutions are ranked with respect to T weight vectors based on two metrics --- the weighted min-max aggregate and the vector angle distance scaling (VADS) metric --- producing 2*T scores/rankings. The overall ranking of a solution is computed using a lexicographical ordering, where the best rank is given to the solution with the best individual ranking among the T weight vectors.

Three methods of constraint handling are described in the literature. In the original paper, [1], E. Hughes recommends ranking feasible and infeasible solutions separately and ensuring the ranking if worse for the infeasible solutions. In the published Matlab code, [2], E. Hughes penalizes the objective values based on the magnitude of the constraint violation. Lastly, in [3], E. Hughes states that the infeasible solutions are ranked in order by their aggregate constraint violation. Regardless of these differences, all three methods ensure the ranking is always worse for infeasible solutions. This implementation follows this practice by penalizing the scores based on the magnitude of the constraint violation (similar to [2]).

References:

  1. E. J. Hughes. "Multiple Single Objective Pareto Sampling." 2003 Congress on Evolutionary Computation, pp. 2678-2684.
  2. Matlab source code available from http://code.evanhughes.org/.
  3. E. J. Hughes. "MSOPS-II: A general-purpose many-objective optimizer." 2007 IEEE Congress on Evolutionary Computation, pp. 3944-3951.
  4. E. J. Hughes. "Evolutionary many-objective optimization: many once or one many." 2005 IEEE Congress on Evolutionary Computation, pp. 222-227.


Constructor Summary
MSOPSRankedPopulation(List<double[]> weights)
          Constructs an empty population that maintains the rank and attribute for its solutions using the MSOPS ranking method.
MSOPSRankedPopulation(List<double[]> weights, Iterable<? extends Solution> iterable)
          Constructs a population initialized with the specified solutions that maintains the rank attribute for its solutions using the MSOPS ranking method.
 
Method Summary
 boolean add(Solution solution)
          Adds the specified solution to this population.
 void clear()
          Removes all solutions from this population.
 Population findNearest(int index, int size)
          Returns the neighborhood of solutions nearest to and including the given solution.
 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 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 replace(int index, Solution solution)
          Replaces the solution at the given index.
 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 RankComparator()).
 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 attribute of all solutions in this population using the MSOPS ranking method.
 
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

MSOPSRankedPopulation

public MSOPSRankedPopulation(List<double[]> weights)
Constructs an empty population that maintains the rank and attribute for its solutions using the MSOPS ranking method.

Parameters:
weights - the weight vectors

MSOPSRankedPopulation

public MSOPSRankedPopulation(List<double[]> weights,
                             Iterable<? extends Solution> iterable)
Constructs a population initialized with the specified solutions that maintains the rank attribute for its solutions using the MSOPS ranking method.

Parameters:
weights - the weight vectors
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.

replace

public void replace(int index,
                    Solution solution)
Description copied from class: Population
Replaces the solution at the given index.

Overrides:
replace in class Population
Parameters:
index - the index to replace
solution - the new solution

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

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 RankComparator()).

Parameters:
size - the target population size after truncation

findNearest

public Population findNearest(int index,
                              int size)
Returns the neighborhood of solutions nearest to and including the given solution.

Parameters:
index - the index of the solution at the center of the neighborhood
size - the size of the neighborhood
Returns:
the solutions in the neighborhood

update

public void update()
Updates the rank attribute of all solutions in this population using the MSOPS ranking method. 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.


MOEA Framework 2.12
API Specification

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