Package org.cicirello.search.restarts

Class ReoptimizableMultistarter<T extends Copyable<T>>

java.lang.Object

org.cicirello.search.restarts.Multistarter<T>

org.cicirello.search.restarts.ReoptimizableMultistarter<T>

Type Parameters:

T - The type of object being optimized.

All Implemented Interfaces:

Splittable<TrackableSearch<T>>, Metaheuristic<T>, ReoptimizableMetaheuristic<T>, TrackableSearch<T>

public final class ReoptimizableMultistarter<T extends Copyable<T>>
extends Multistarter<T>
implements ReoptimizableMetaheuristic<T>

This class is used for implementing multistart metaheuristics, that can be restarted at previously found solutions. It can be used to restart any class that implements the ReoptimizableMetaheuristic interface, and requires specification of either a RestartSchedule for the purpose of specifying run lengths for the restarts, or a run length if all runs are to be of the same length. A multistart metaheuristic returns the best result from among all of the restarts.

Constructor Summary

Constructors

Constructor	Description
ReoptimizableMultistarter(ReoptimizableMetaheuristic<T> search, int runLength)	Constructs a multistart metaheuristic that executes multiple runs of a specified metaheuristic, whose runs are all the same in length.
ReoptimizableMultistarter(ReoptimizableMetaheuristic<T> search, RestartSchedule r)	Constructs a multistart metaheuristic that executes multiple runs of a specified metaheuristic, whose run lengths follow a specified schedule.

Method Summary

Modifier and Type	Method	Description
SolutionCostPair<T>	reoptimize(int numRestarts)	Executes a multistart search, calling the underlying metaheuristic the specified number of times, keeping track of the best solution across the multiple runs of the search.
ReoptimizableMultistarter<T>	split()	Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms.

Methods inherited from class org.cicirello.search.restarts.Multistarter

getProblem, getProgressTracker, getTotalRunLength, optimize, setProgressTracker

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.cicirello.search.Metaheuristic

optimize

Methods inherited from interface org.cicirello.search.TrackableSearch

getProblem, getProgressTracker, getTotalRunLength, setProgressTracker

Constructor Detail

ReoptimizableMultistarter

public ReoptimizableMultistarter(ReoptimizableMetaheuristic<T> search,
                                 RestartSchedule r)

Constructs a multistart metaheuristic that executes multiple runs of a specified metaheuristic, whose run lengths follow a specified schedule.

Parameters:

search - The metaheuristic to restart multiple times.

r - The schedule of run lengths for the multistart search

ReoptimizableMultistarter

public ReoptimizableMultistarter(ReoptimizableMetaheuristic<T> search,
                                 int runLength)

Constructs a multistart metaheuristic that executes multiple runs of a specified metaheuristic, whose runs are all the same in length.

Parameters:

search - The metaheuristic to restart multiple times.

runLength - The length of every restarted run of the metaheuristic.

Throws:

IllegalArgumentException - if runLength < 1

Method Detail

reoptimize

public SolutionCostPair<T> reoptimize(int numRestarts)

Executes a multistart search, calling the underlying metaheuristic the specified number of times, keeping track of the best solution across the multiple runs of the search. Each restart begins at the best solution found so far, but reinitializes any search control parameters.

If this method is called multiple times, the restart schedule is not reinitialized, and the run lengths for the additional restarts will continue where the schedule left off.

Specified by:

reoptimize in interface ReoptimizableMetaheuristic<T extends Copyable<T>>

Parameters:

numRestarts - The number of times to restart the metaheuristic.

Returns:

The best end of run solution (and its cost) of this set of restarts, which may or may not be the same as the solution contained in this metaheuristic's ProgressTracker, which contains the best of all runs. Returns null if the run did not execute, such as if the ProgressTracker already contains the theoretical best solution.

split

public ReoptimizableMultistarter<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 Metaheuristic<T extends Copyable<T>>

Specified by:

split in interface ReoptimizableMetaheuristic<T extends Copyable<T>>

Specified by:

split in interface Splittable<T extends Copyable<T>>

Overrides:

split in class Multistarter<T extends Copyable<T>>

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.