Package org.moeaframework.core
Class NondominatedSortingPopulation
java.lang.Object
org.moeaframework.core.Population
org.moeaframework.core.NondominatedSortingPopulation
- All Implemented Interfaces:
Iterable<Solution>
,Stateful
,Displayable
,Formattable<Solution>
- Direct Known Subclasses:
ReferencePointNondominatedSortingPopulation
Population that maintains the
rank
and crowdingDistance
attributes for its solutions by invoking
NondominatedSorting.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.
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Constructor Summary
ConstructorDescriptionConstructs an empty population that maintains therank
andcrowdingDistance
attributes for its solutions.NondominatedSortingPopulation
(Iterable<? extends Solution> iterable) Constructs a population initialized with the specified solutions that maintains therank
andcrowdingDistance
attributes for its solutions.NondominatedSortingPopulation
(DominanceComparator comparator) Constructs an empty population that maintains therank
andcrowdingDistance
attributes for its solutions.NondominatedSortingPopulation
(DominanceComparator comparator, Iterable<? extends Solution> iterable) Constructs a population initialized with the specified solutions that maintains therank
andcrowdingDistance
attributes for its solutions. -
Method Summary
Modifier and TypeMethodDescriptionboolean
Adds the specified solution to this population.void
clear()
Removes all solutions from this population.copy()
Returns a copy of this population.get
(int index) Returns the solution at the specified index in this population.Returns the dominance comparator used by this non-dominated population.iterator()
Returns an iterator for accessing the solutions in this population.void
loadState
(ObjectInputStream stream) Loads the state of this object from the stream.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
Removes the specified solution from this population, if present.void
Replaces the solution at the given index.void
saveState
(ObjectOutputStream stream) Writes the state of this object to the stream.void
sort
(Comparator<? super Solution> comparator) Sorts the solutions in this population using the specified comparator.void
truncate
(int size) Equivalent to callingtruncate(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, asList, asTabularData, contains, containsAll, containsAll, filter, getLowerBounds, getUpperBounds, indexOf, isEmpty, loadBinary, loadBinary, loadObjectives, loadObjectives, removeAll, removeAll, removeAll, saveBinary, saveBinary, saveObjectives, saveObjectives, 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, saveCSV
Methods inherited from interface java.lang.Iterable
forEach, spliterator
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Constructor Details
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NondominatedSortingPopulation
public NondominatedSortingPopulation()Constructs an empty population that maintains therank
andcrowdingDistance
attributes for its solutions. -
NondominatedSortingPopulation
Constructs an empty population that maintains therank
andcrowdingDistance
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 therank
andcrowdingDistance
attributes for its solutions.- Parameters:
comparator
- the dominance comparatoriterable
- the solutions used to initialize this population
-
NondominatedSortingPopulation
Constructs a population initialized with the specified solutions that maintains therank
andcrowdingDistance
attributes for its solutions.- Parameters:
iterable
- the solutions used to initialize this population
-
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Method Details
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getComparator
Returns the dominance comparator used by this non-dominated population.- Returns:
- the dominance comparator
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add
Description copied from class:Population
Adds the specified solution to this population.- Overrides:
add
in classPopulation
- Parameters:
solution
- the solution to be added- Returns:
true
if the population was modified as a result of this method;false
otherwise.
-
replace
Description copied from class:Population
Replaces the solution at the given index.- Overrides:
replace
in classPopulation
- Parameters:
index
- the index to replacesolution
- the new solution
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get
Description copied from class:Population
Returns the solution at the specified index in this population.- Overrides:
get
in classPopulation
- Parameters:
index
- the index of the solution to be returned- Returns:
- the solution at the specified index
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remove
public void remove(int index) Description copied from class:Population
Removes the solution at the specified index from this population.- Overrides:
remove
in classPopulation
- Parameters:
index
- the index of the solution to be removed
-
remove
Description copied from class:Population
Removes the specified solution from this population, if present.- Overrides:
remove
in classPopulation
- Parameters:
solution
- the solution to be removed- Returns:
true
if this population was modified as a result of this method;false
otherwise
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clear
public void clear()Description copied from class:Population
Removes all solutions from this population.- Overrides:
clear
in classPopulation
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iterator
Description copied from class:Population
Returns an iterator for accessing the solutions in this population.- Specified by:
iterator
in interfaceIterable<Solution>
- Overrides:
iterator
in classPopulation
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sort
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 theget
,remove
and iteration methods should be called immediately after invoking this method.- Overrides:
sort
in classPopulation
- Parameters:
comparator
- the comparator to be used for sorting
-
truncate
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 classPopulation
- Parameters:
size
- the target population size after truncationcomparator
- the comparator to be used for truncation
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truncate
public void truncate(int size) Equivalent to callingtruncate(size, new NondominatedSortingComparator())
.- Parameters:
size
- the target population size after truncation
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prune
public void prune(int size) Prunes the population to the specified size. This is similar totruncate(int)
, except the crowding distance is recalculated each time a solution is removed.- Parameters:
size
- the target population size after pruning
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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 invokeupdate()
manually. -
copy
Description copied from class:Population
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)
orPopulation.addAll(Iterable)
whenever possible. These alternatives are useful when filtering or reordering the solutions, but the solutions themselves are left unchanged.- Overrides:
copy
in classPopulation
- Returns:
- the copy of this population
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saveState
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 callingsuper.saveState(stream)
followed by writing each field.- Specified by:
saveState
in interfaceStateful
- Overrides:
saveState
in classPopulation
- Parameters:
stream
- the stream- Throws:
IOException
- if an I/O error occurred
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loadState
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 inStateful.saveState(ObjectOutputStream)
.- Specified by:
loadState
in interfaceStateful
- Overrides:
loadState
in classPopulation
- Parameters:
stream
- the stream- Throws:
IOException
- if an I/O error occurredClassNotFoundException
- if the stream referenced a class that is not defined
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