ec

Class Problem

java.lang.Object

ec.Problem

All Implemented Interfaces:

Prototype, Setup, Serializable, Cloneable

Direct Known Subclasses:

AddSubtract, BBOBenchmarks, CartPole, CompetitiveMaxOnes, ECSuite, GEProblem, GPProblem, HIFF, HighDimension, KnapsackProblem, MajorityGA, MasterProblem, MaxOnes, MetaProblem, Mona, MooSuite, NK, OddRosenbrock, SAT, Singular, Sum, TSPProblem, XOR

public abstract class Problem
extends Object
implements Prototype

Problem is a prototype which defines the problem against which we will evaluate individuals in a population.

Since Problems are Prototypes, you should expect a new Problem class to be cloned and used, on a per-thread basis, for the evolution of each chunk of individuals in a new population. If you for some reason need global Problem information, you will have to provide it statically, or copy pointers over during the clone() process (there is likely only one Problem prototype, depending on the Evaluator class used).

Note that Problem does not implement a specific evaluation method. Your particular Problem subclass will need to implement a some kind of Problem Form (for example, SimpleProblemForm) appropriate to the kind of evaluation being performed on the Problem. These Problem Forms will provide the evaluation methods necessary.

Problem forms will define some kind of evaluation method. This method may be called in one of two ways by the Evaluator.

• The evaluation is called for a series of individuals. This is the old approach, and it means that each individual must be evaluated and modified as specified by the Problem Form during the evaluation call.
• prepareToEvaluate is called, then a series of individuals is evaluated, and then finishEvaluating is called. This is the new approach, and in this case the Problem is free to delay evaluating and modifying the individuals until finishEvaluating has been called. The Problem may perfectly well evaluate and modify the individuals during each evaluation call if it likes. It's just given this additional option.

Problems should be prepared for both of the above situations. The easiest way to handle it is to simply evaluate each individual as his evaluate(...) method is called, and do nothing during prepareToEvaluate or finishEvaluating. That should be true for the vast majority of Problem types.

Version:

2.0

Author:

Sean Luke

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static String	P_PROBLEM

Constructor Summary

Constructors

Constructor and Description
Problem()

Method Summary

Modifier and Type	Method and Description
boolean	canEvaluate() Asynchronous Steady-State EC only: Returns true if the problem is ready to evaluate.
Object	clone() Creates a new individual cloned from a prototype, and suitable to begin use in its own evolutionary context.
void	closeContacts(EvolutionState state, int result) Called to shut down remote evaluation network contacts when the run is completed.
Parameter	defaultBase() Here's a nice default base for you -- you can change it if you like
void	describe(EvolutionState state, Individual ind, int subpopulation, int threadnum, int log) Part of SimpleProblemForm.
void	describe(Individual ind, EvolutionState state, int subpopulation, int threadnum, int log, int verbosity) Deprecated. Use the version without verbosity
void	finishEvaluating(EvolutionState state, int threadnum) Will be called by the Evaluator after prepareToEvaluate(...) is called and then a series of individuals are evaluated.
void	initializeContacts(EvolutionState state) Called to set up remote evaluation network contacts when the run is started.
void	prepareToEvaluate(EvolutionState state, int threadnum) May be called by the Evaluator prior to a series of individuals to evaluate, and then ended with a finishEvaluating(...).
void	reinitializeContacts(EvolutionState state) Called to reinitialize remote evaluation network contacts when the run is restarted from checkpoint.
void	setup(EvolutionState state, Parameter base) Sets up the object by reading it from the parameters stored in state, built off of the parameter base base.

Methods inherited from class java.lang.Object

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

Field Detail

P_PROBLEM

public static final String P_PROBLEM

See Also:

Constant Field Values

Constructor Detail

Problem

public Problem()

Method Detail

defaultBase

public Parameter defaultBase()

Here's a nice default base for you -- you can change it if you like

Specified by:

defaultBase in interface Prototype

setup

public void setup(EvolutionState state,
                  Parameter base)

Description copied from interface: Prototype

Sets up the object by reading it from the parameters stored in state, built off of the parameter base base. If an ancestor implements this method, be sure to call super.setup(state,base); before you do anything else.

For prototypes, setup(...) is typically called once for the prototype instance; cloned instances do not receive the setup(...) call. setup(...) may be called more than once; the only guarantee is that it will get called at least once on an instance or some "parent" object from which it was ultimately cloned.

Specified by:

setup in interface Prototype

Specified by:

setup in interface Setup

clone

public Object clone()

Description copied from interface: Prototype

Creates a new individual cloned from a prototype, and suitable to begin use in its own evolutionary context.

Typically this should be a full "deep" clone. However, you may share certain elements with other objects rather than clone hem, depending on the situation:

• If you hold objects which are shared with other instances, don't clone them.
• If you hold objects which must be unique, clone them.
• If you hold objects which were given to you as a gesture of kindness, and aren't owned by you, you probably shouldn't clone them.
• DON'T attempt to clone: Singletons, Cliques, or Populations, or Subpopulation.
• Arrays are not cloned automatically; you may need to clone an array if you're not sharing it with other instances. Arrays have the nice feature of being copyable by calling clone() on them.

Implementations.

• If no ancestor of yours implements clone(), and you have no need to do clone deeply, and you are abstract, then you should not declare clone().
• If no ancestor of yours implements clone(), and you have no need to do clone deeply, and you are not abstract, then you should implement it as follows:

   public Object clone() 
       {
       try
           { 
           return super.clone();
           }
       catch ((CloneNotSupportedException e)
           { throw new InternalError(); } // never happens
       }
          

• If no ancestor of yours implements clone(), but you need to deep-clone some things, then you should implement it as follows:

   public Object clone() 
       {
       try
           { 
           MyObject myobj = (MyObject) (super.clone());
  
           // put your deep-cloning code here...
           }
       catch ((CloneNotSupportedException e)
           { throw new InternalError(); } // never happens
       return myobj;
       } 
          

• If an ancestor has implemented clone(), and you also need to deep clone some things, then you should implement it as follows:

   public Object clone() 
       { 
       MyObject myobj = (MyObject) (super.clone());
  
       // put your deep-cloning code here...
  
       return myobj;
       } 
          

Specified by:

clone in interface Prototype

Overrides:

clone in class Object

prepareToEvaluate

public void prepareToEvaluate(EvolutionState state,
                              int threadnum)

May be called by the Evaluator prior to a series of individuals to evaluate, and then ended with a finishEvaluating(...). If this is the case then the Problem is free to delay modifying the individuals or their fitnesses until at finishEvaluating(...). If no prepareToEvaluate(...) is called prior to evaluation, the Problem must complete its modification of the individuals and their fitnesses as they are evaluated as stipulated in the relevant evaluate(...) documentation for SimpleProblemForm or GroupedProblemForm. The default method does nothing. Note that prepareToEvaluate() can be called *multiple times* prior to finishEvaluating() being called -- in this case, the subsequent calls may be ignored.

finishEvaluating

public void finishEvaluating(EvolutionState state,
                             int threadnum)

Will be called by the Evaluator after prepareToEvaluate(...) is called and then a series of individuals are evaluated. However individuals may be evaluated without prepareToEvaluate or finishEvaluating being called at all. See the documentation for prepareToEvaluate for more information. The default method does nothing.

initializeContacts

public void initializeContacts(EvolutionState state)

Called to set up remote evaluation network contacts when the run is started. By default does nothing.

reinitializeContacts

public void reinitializeContacts(EvolutionState state)

Called to reinitialize remote evaluation network contacts when the run is restarted from checkpoint. By default does nothing.

closeContacts

public void closeContacts(EvolutionState state,
                          int result)

Called to shut down remote evaluation network contacts when the run is completed. By default does nothing.

canEvaluate

public boolean canEvaluate()

Asynchronous Steady-State EC only: Returns true if the problem is ready to evaluate. In most cases, the default is true.

describe

public void describe(EvolutionState state,
                     Individual ind,
                     int subpopulation,
                     int threadnum,
                     int log)

Part of SimpleProblemForm. Included here so you don't have to write the default version, which usually does nothing.

describe

public final void describe(Individual ind,
                           EvolutionState state,
                           int subpopulation,
                           int threadnum,
                           int log,
                           int verbosity)

Deprecated. Use the version without verbosity