Module org.cicirello.chips_n_salsa

Package org.cicirello.search.operators.integers

Class UndoableUniformMutation<T extends IntegerValued>

java.lang.Object

org.cicirello.search.operators.integers.UndoableUniformMutation<T>

Type Parameters:

T - The specific IntegerValued type.

All Implemented Interfaces:

Splittable<MutationOperator<T>>, MutationOperator<T>, UndoableMutationOperator<T>, IntegerValued, Copyable<UndoableUniformMutation<T>>

public class UndoableUniformMutation<T extends IntegerValued>
extends Object
implements Copyable<UndoableUniformMutation<T>>

This class implements a uniform mutation with support for the UndoableMutationOperator.undo(T) method. This uniform mutation is for mutating integer values. This class can be used to mutate objects of any of the classes that implement the IntegerValued interface, including both univariate and multivariate objects.

In the form of uniform mutation implemented by this class, a value v is mutated by adding a randomly generated m such that m is drawn uniformly at random from the interval [-radius, radius].

This mutation operator also implements the IntegerValued interface to enable implementation of metaheuristics that mutate their own mutation parameters. That is, you can pass an UndoableUniformMutation object to the MutationOperator.mutate(T) method of a UndoableUniformMutation object.

To construct an UndoableUniformMutation, you must use one of the factory methods. See the various createUniformMutation() methods.

Method Summary

Modifier and Type	Method	Description
UndoableUniformMutation<T>	copy()	Creates an identical copy of this object.
static <T extends IntegerValued> UndoableUniformMutation<T>	createUniformMutation()	Creates a Uniform mutation operator with radius parameter equal to 1 that supports the undo operation.
static <T extends IntegerValued> UndoableUniformMutation<T>	createUniformMutation(int radius)	Creates a Uniform mutation operator that supports the undo operation.
static <T extends IntegerValued> UndoableUniformMutation<T>	createUniformMutation(int radius, double p)	Create a Uniform mutation operator that supports the undo operation.
static <T extends IntegerValued> UndoableUniformMutation<T>	createUniformMutation(int radius, int k)	Create a Uniform mutation operator that supports the undo operation.
static <T extends IntegerValued> UndoableUniformMutation<T>	createUniformMutation(int radius, int lowerBound, int upperBound)	Creates a Uniform mutation operator, such that the mutate method constrains each mutated int value to lie in the interval [lowerBound, upperBound].
final int	get(int i)	Accesses the current value of the mutation parameter.
final int	length()	Gets the number of parameters.
final void	mutate(T c)	Mutates a candidate solution to a problem, by randomly modifying its state.
final void	set(int[] values)	Sets the mutation parameter to a specified value.
final void	set(int i, int value)	Sets the mutation parameter to a specified value.
UndoableUniformMutation<T>	split()	Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms.
final int[]	toArray(int[] values)	Accesses the current value of the mutation parameter as an array.
final void	undo(T c)	Returns a candidate solution to its previous state prior to the most recent mutation performed.

Methods inherited from class java.lang.Object

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

Method Details

createUniformMutation

public static <T extends IntegerValued>
UndoableUniformMutation<T> createUniformMutation()

Creates a Uniform mutation operator with radius parameter equal to 1 that supports the undo operation.

Type Parameters:

T - The specific IntegerValued type.

Returns:

A Uniform mutation operator.

createUniformMutation

public static <T extends IntegerValued>
UndoableUniformMutation<T> createUniformMutation(int radius)

Creates a Uniform mutation operator that supports the undo operation.

Type Parameters:

T - The specific IntegerValued type.

Parameters:

radius - The radius parameter of the Uniform.

Returns:

A Uniform mutation operator.

createUniformMutation

public static <T extends IntegerValued>
UndoableUniformMutation<T> createUniformMutation(int radius,
 int lowerBound,
 int upperBound)

Creates a Uniform mutation operator, such that the mutate method constrains each mutated int value to lie in the interval [lowerBound, upperBound].

Type Parameters:

T - The specific IntegerValued type.

Parameters:

radius - The radius parameter of the Uniform.

lowerBound - A lower bound on the result of a mutation.

upperBound - An upper bound on the result of a mutation.

Returns:

A Uniform mutation operator.

createUniformMutation

public static <T extends IntegerValued>
UndoableUniformMutation<T> createUniformMutation(int radius,
 int k)

Create a Uniform mutation operator that supports the undo operation.

Type Parameters:

T - The specific IntegerValued type.

Parameters:

radius - The radius parameter of the Uniform mutation.

k - The number of input variables that the MutationOperator.mutate(T) method changes when called. The k input variables are chosen uniformly at random from among all subsets of size k. If there are less than k input variables, then all are mutated.

Returns:

A Uniform mutation operator

Throws:

IllegalArgumentException - if k < 1

createUniformMutation

public static <T extends IntegerValued>
UndoableUniformMutation<T> createUniformMutation(int radius,
 double p)

Create a Uniform mutation operator that supports the undo operation.

Type Parameters:

T - The specific IntegerValued type.

Parameters:

radius - The radius parameter of the Uniform mutation.

p - The probability that the MutationOperator.mutate(T) method changes an input variable. If there are n input variables, then n*p input variables will be mutated on average during a single call to the MutationOperator.mutate(T) method.

Returns:

A Uniform mutation operator

Throws:

IllegalArgumentException - if p ≤ 0

split

public UndoableUniformMutation<T> split()

Description copied from interface: Splittable

Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms. The state of the object that is returned may or may not be identical to that of the original. Thus, this is a distinct concept from the functionality of the Copyable interface. Classes that implement this interface must ensure that the object returned performs the same functionality, and that it does not share any state data that would be either unsafe or inefficient for concurrent access by multiple threads. The split method is allowed to simply return the this reference, provided that it is both safe and efficient for multiple threads to share a single copy of the Splittable object. The intention is to provide a multithreaded search with the capability to provide spawned threads with their own distinct search operators. Such multithreaded algorithms can call the split method for each thread it spawns to generate a functionally identical copy of the operator, but with independent state.

Specified by:

split in interface Splittable<T extends IntegerValued>

Specified by:

split in interface UndoableMutationOperator<T extends IntegerValued>

Returns:

A functionally identical copy of the object, or a reference to this if it is both safe and efficient for multiple threads to share a single instance of this Splittable object.

copy

public UndoableUniformMutation<T> copy()

Creates an identical copy of this object.

Specified by:

copy in interface Copyable<T extends IntegerValued>

Returns:

an identical copy of this object

mutate

public final void mutate(T c)

Description copied from interface: MutationOperator

Mutates a candidate solution to a problem, by randomly modifying its state. The mutant that is produced is in the local neighborhood of the original candidate solution.

Specified by:

mutate in interface MutationOperator<T extends IntegerValued>

Parameters:

c - The candidate solution subject to the mutation. This method changes the state of c.

undo

public final void undo(T c)

Description copied from interface: UndoableMutationOperator

Returns a candidate solution to its previous state prior to the most recent mutation performed.

For example, consider the following. Let c' be the current state of c. Let c'' be the state of c after mutate(c); If we then call undo(c), the state of c should revert back to c'.

The behavior of undo is undefined if c is altered by some other process between the calls to mutate and undo. The behavior is also undefined if a different candidate is given to undo then the last given to mutate. For example, if the following two statements are executed, mutate(c); undo(d);, the effect on d is undefined as it wasn't the most recently mutated candidate solution.

Specified by:

undo in interface UndoableMutationOperator<T extends IntegerValued>

Parameters:

c - The candidate solution to revert.

length

public final int length()

Description copied from interface: IntegerValued

Gets the number of parameters.

Specified by:

length in interface IntegerValued

Returns:

The number of parameters for this function.

get

public final int get(int i)

Accesses the current value of the mutation parameter.

Specified by:

get in interface IntegerValued

Parameters:

i - Ignored.

Returns:

The current value of the mutation parameter.

toArray

public final int[] toArray(int[] values)

Accesses the current value of the mutation parameter as an array. This method implemented strictly to meet implementation requirements of IntegerValued interface.

Specified by:

toArray in interface IntegerValued

Parameters:

values - An array to hold the result. If values is null or if values.length is not equal 1, then a new array is constructed for the result.

Returns:

An array containing the current value of the mutation parameter.

set

public final void set(int i,
 int value)

Sets the mutation parameter to a specified value.

Specified by:

set in interface IntegerValued

Parameters:

i - Ignored.

value - The new value for the mutation parameter.

set

public final void set(int[] values)

Sets the mutation parameter to a specified value.

Specified by:

set in interface IntegerValued

Parameters:

values - The new value for the mutation parameter is in values[0], the rest is ignored.