Problem

java.lang.Object
-
- jcgp.backend.modules.Module
- -
  - jcgp.backend.modules.problem.Problem
  -
-

-
-
Direct Known Subclasses:
-
TestCaseProblem
-
-
-
-
```
public abstract class Problem
-extends Module
```
-
Defines the general behaviour of a CGP problem. The primary function of Problem - is to evaluate a population and assign a fitness value to each chromosome. -
- Problems are free to define whether better fitness means a higher or lower fitness value. - In some problem types, it is more convenient to treat fitness 0 as the best possible value. - This can be done by changing the fitness orientation to BestFitness.HIGH or BestFitness.LOW as appropriate. - Fitness orientation is set to high by default. -

- When extending this class, the constructor should call a few methods in order to - properly construct the problem type: setFunctionSet(), setFileExtension() and setFitnessOrientation(), - with the respective arguments. As with all subclasses of Module, setName() and - registerParameters() should be used where appropriate as well. -

- It is advisable to use Resources.reportln() and Resources.report() - to print any relevant information. Note that reportln() and report() are affected - by the report interval base parameter. Use Resources.println() and - Resources.print() to print information regardless of the current generation. - See Resources for more information.
-
-
Author:
-
Eduardo Pedroni
-
See Also:
-
Module
-
-

- -

Method Summary

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract void`	`evaluate(Population population)` - The most important method of the problem type. -
`double`	`getBestFitness()`
`java.lang.String`	`getFileExtension()`
`BestFitness`	`getFitnessOrientation()`
`FunctionSet`	`getFunctionSet()`
`abstract int`	`hasImprovement(Population population)` - Used to assert whether a given population has a chromosome that is an improvement over - the current best chromosome. -
`abstract int`	`hasPerfectSolution(Population population)` - Used to assert whether a given population contains a perfect solution - to the problem. -
`abstract void`	`parseProblemData(java.io.File file, - ModifiableResources resources)` - Parses the specified file and uses the parsed data to - set up the problem type instance appropriately. -
`void`	`reset()` - Resets the bestFitness parameter. -

- - -
Methods inherited from class jcgp.backend.modules.Module
-getLocalParameters, toString

- - -
Methods inherited from class java.lang.Object
-equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- -
- - - -
  Method Detail
  - - - -
  - -
    evaluate
    -
```
public abstract void evaluate(Population population)
```
    -
    The most important method of the problem type. This is called once - per generation, when the new population has been generated. -
    
    - The basic functionality of this method is to loop through all chromosomes - in the population and decode them according to the problem type. The - fitness of each chromosome is then calculated using the problem data - or otherwise (subjective problem types such as art generation might - leave fitness evaluations up to the user) and assigned to the appropriate - chromosome. -
    
    - In addition, realisations of this method should update the value of - bestFitness as appropriate, since the value of this parameter is displayed - if a GUI is in use.
    -
    -
    Parameters:
    -
    population - the population to be evaluated.
    -
    -
  - - - -
  - -
    hasPerfectSolution
    -
```
public abstract int hasPerfectSolution(Population population)
```
    -
    Used to assert whether a given population contains a perfect solution - to the problem. It is up to the problem to define what qualifies - a perfect solution, as some problems (subject ones such as music and - art evolution, for example) might not have perfect solutions at all.
    -
    -
    Parameters:
    -
    population - the population to search through for a perfect chromosome.
    -
    Returns:
    -
    the perfect solution index, if one exits, -1 if no perfect solution was found.
    -
    -
  - - - -
  - -
    hasImprovement
    -
```
public abstract int hasImprovement(Population population)
```
    -
    Used to assert whether a given population has a chromosome that is an improvement over - the current best chromosome. A typical implementation of this method - will simply compare chromosome fitness values, though the problem type - is free to implement this in any way.
    -
    -
    Parameters:
    -
    population - the population potentially containing a fitter chromosome.
    -
    Returns:
    -
    the index of the first chromosome in the population that is an improvement, -1 if none is found.
    -
    -
  - - - -
  - -
    parseProblemData
    -
```
public abstract void parseProblemData(java.io.File file,
-                                      ModifiableResources resources)
```
    -
    Parses the specified file and uses the parsed data to - set up the problem type instance appropriately. Any necessary - resource changes can be performed using the provided ModifiableResources - instance. -
    
    - In addition, realisations of this method should update the value of - maxFitness where appropriate, as this may be displayed to the user - if a GUI is in use.
    -
    -
    Parameters:
    -
    file - the data file to parse.
    -
    resources - a modifiable reference to the experiment's resources.
    -
    -
  - - - -
  - -
    getFunctionSet
    -
```
public FunctionSet getFunctionSet()
```
    -
    -
    Returns:
    -
    the FunctionSet object used by this problem type.
    -
    -
  - - - -
  - -
    getFileExtension
    -
```
public java.lang.String getFileExtension()
```
    -
    -
    Returns:
    -
    the file extension accepted by this problem type for problem data files.
    -
    -
  - - - -
  - -
    getFitnessOrientation
    -
```
public BestFitness getFitnessOrientation()
```
    -
    -
    Returns:
    -
    the fitness orientation of this particular problem.
    -
    -
  - - - -
  - -
    getBestFitness
    -
```
public double getBestFitness()
```
    -
    -
    Returns:
    -
    the current best fitness, in other words, the fitness - value of the fittest chromosome in the current generation.
    -
    -
  - - - -
  - -
    reset
    -
```
public void reset()
```
    -
    Resets the bestFitness parameter.
    -
  -
-

Class Problem

Method Summary

Methods inherited from class jcgp.backend.modules.Module

Methods inherited from class java.lang.Object

Method Detail

evaluate

hasPerfectSolution

hasImprovement

parseProblemData

getFunctionSet

getFileExtension

getFitnessOrientation

getBestFitness

reset