Package org.moeaframework.algorithm

Class AbstractAlgorithm

java.lang.Object
org.moeaframework.algorithm.AbstractAlgorithm
All Implemented Interfaces:
Extensible, Algorithm, Stateful
Direct Known Subclasses:
AbstractEvolutionaryAlgorithm, AbstractPSOAlgorithm, AbstractSimulatedAnnealingAlgorithm, CMAES, MOEAD, RandomSearch, RepeatedSingleObjective
public abstract class AbstractAlgorithm extends Object implements Algorithm
Abstract class providing default implementations for several Algorithm methods.

When creating a new subclass, one should:

  1. Use the evaluate(org.moeaframework.core.Solution) or Algorithm.evaluateAll(java.lang.Iterable<org.moeaframework.core.Solution>) methods provided by this class. Do not call Problem.evaluate(org.moeaframework.core.Solution) directly as that will not count the number of function evaluations correctly.
  2. When possible, prefer evaluating all solutions at once by calling Algorithm.evaluateAll(java.lang.Iterable<org.moeaframework.core.Solution>). Doing so allows function evaluations to run in parallel when enabled (see Executor#distributeOnAllCores()).
  3. Implement the algorithm by overriding the initialize() and iterate() methods.

  • Field Details

    • problem

      protected final Problem problem
      The problem being solved.

    • numberOfEvaluations

      protected int numberOfEvaluations
      The number of times the evaluate(org.moeaframework.core.Solution) method was invoked.

    • initialized

      protected boolean initialized
      true if the initialize() method has been invoked; false otherwise.

    • terminated

      protected boolean terminated
      true if the terminate() method has been invoked; false otherwise.

  • Constructor Details

    • AbstractAlgorithm

      public AbstractAlgorithm(Problem problem)
      Constructs an abstract algorithm for solving the specified problem.
      Parameters:
      problem - the problem being solved

  • Method Details

    • evaluate

      public void evaluate(Solution solution)
      Description copied from interface: Algorithm
      Evaluates the specified solution for the problem being solved by this algorithm.
      Specified by:
      evaluate in interface Algorithm
      Parameters:
      solution - the solution to be evaluated
      See Also:

    • getNumberOfEvaluations

      public int getNumberOfEvaluations()
      Description copied from interface: Algorithm
      Returns the number of times the evaluate method was invoked. This is the primary measure of runtime for optimization algorithms.
      Specified by:
      getNumberOfEvaluations in interface Algorithm
      Returns:
      the number of times the evaluate method was invoked

    • getProblem

      public Problem getProblem()
      Description copied from interface: Algorithm
      Returns the problem being solved by this algorithm.
      Specified by:
      getProblem in interface Algorithm
      Returns:
      the problem being solved by this algorithm

    • initialize

      public void initialize()
      Description copied from interface: Algorithm
      Performs any initialization that is required by this algorithm. This method should only be called once, though the specific implementation may choose to no-op or throw AlgorithmInitializationException if called multiple times.

      Implementations should always call super.initialize() to ensure the algorithm is initialized correctly.

      Specified by:
      initialize in interface Algorithm

    • isInitialized

      public boolean isInitialized()
      Description copied from interface: Algorithm
      Returns true if this algorithm has been initialized; false otherwise.
      Specified by:
      isInitialized in interface Algorithm
      Returns:
      true if this algorithm has been initialized; false otherwise
      See Also:

    • assertNotInitialized

      public void assertNotInitialized()
      Throws an exception if the algorithm is initialized. Use this anywhere to check and fail if the algorithm is already initialized.
      Throws:
      AlgorithmInitializationException - if the algorithm is initialized

    • step

      public void step()
      Performs one logical step of this algorithm. The amount of work performed depends on the implementation. One invocation of this method may produce one or many trial solutions.

      In general, calling this method after Algorithm.terminate() is permitted. When this happens, Algorithm.isTerminated() is reset. We recommend checking Algorithm.isTerminated() after each step to detect when termination conditions are reached. However, if the implementation is unable to continue, this method should throw AlgorithmTerminationException.

      Avoid overriding this method in subclasses. Instead, prefer overriding initialize() and iterate() with any algorithm-specific details.

      Specified by:
      step in interface Algorithm

    • iterate

      protected abstract void iterate()
      Performs one iteration of the algorithm. This method should be overridden by implementations to perform each logical iteration of the algorithm.

    • isTerminated

      public boolean isTerminated()
      Description copied from interface: Algorithm
      Returns true if this algorithm has reached its termination condition; false otherwise.
      Specified by:
      isTerminated in interface Algorithm
      Returns:
      true if this algorithm has reached its termination condition; false otherwise
      See Also:

    • terminate

      public void terminate()
      Description copied from interface: Algorithm
      Called when the termination condition is reached and the run is complete. This method is automatically called when using Algorithm.run(TerminationCondition), but can also be invoked directly if executing the algorithm step-by-step with Algorithm.step().

      Implementations should always call super.terminate() to ensure the algorithm is terminated correctly.

      Specified by:
      terminate in interface Algorithm

    • getExtensions

      public Extensions getExtensions()
      Description copied from interface: Extensible
      Returns the extensions associated with the algorithm.
      Specified by:
      getExtensions in interface Extensible
      Returns:
      the extensions

    • 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