Module org.cicirello.chips_n_salsa
Package org.cicirello.search.concurrent

Class ParallelReoptimizableMetaheuristic<T extends Copyable<T>>

java.lang.Object
org.cicirello.search.concurrent.ParallelMetaheuristic<T>
org.cicirello.search.concurrent.ParallelReoptimizableMetaheuristic<T>
Type Parameters:
T - The type of object being optimized.
All Implemented Interfaces:
AutoCloseable, Splittable<TrackableSearch<T>>, Metaheuristic<T>, ReoptimizableMetaheuristic<T>, TrackableSearch<T>
Direct Known Subclasses:
ParallelReoptimizableMultistarter
public class ParallelReoptimizableMetaheuristic<T extends Copyable<T>> extends ParallelMetaheuristic<T> implements ReoptimizableMetaheuristic<T>
This class enables running multiple copies of a metaheuristic, or multiple metaheuristics, in parallel with multiple threads. It specifically requires that all metaheuristics are solving the same problem, but otherwise they may be the same or different metaheuristics.

  • Constructor Details

    • ParallelReoptimizableMetaheuristic

      public ParallelReoptimizableMetaheuristic(ReoptimizableMetaheuristic<T> search, int numThreads)
      Constructs a parallel metaheuristic that executes multiple identical copies of a metaheuristic in parallel across multiple threads.
      Parameters:
      search - The metaheuristic to run in parallel.
      numThreads - The number of threads to use.
      Throws:
      IllegalArgumentException - if numThreads is less than 1.

    • ParallelReoptimizableMetaheuristic

      public ParallelReoptimizableMetaheuristic(Collection<? extends ReoptimizableMetaheuristic<T>> searches)
      Constructs a parallel metaheuristic that executes multiple metaheuristics in parallel across multiple threads.
      Parameters:
      searches - A collection of the metaheuristics to run in parallel. The number of threads will be equal to the size of this collection.
      Throws:
      IllegalArgumentException - if the Collection of Metaheuristics don't all share the same problem (i.e., requires that s1.getProblem() == s2.getProblem() for all s1, s2 in searches).
      IllegalArgumentException - if the Collection of Metaheuristics don't all share a single ProgressTracker (i.e., requires that s1.getProgressTracker() == s2.getProgressTracker() for all s1, s2 in searches).

  • Method Details

    • reoptimize

      public final SolutionCostPair<T> reoptimize(int runLength)
      Executes a parallel metaheuristic search. The number of threads, the specific metaheuristic executed by each thread, etc are determined by how the ParallelReoptimizableMetaheuristic was configured at the time of construction. The reoptimize method runs the reoptimize method of each of the parallel instances of the search the specified for the specified run length (identical for all parallel instances), keeping track of the best solution across the multiple parallel runs of the search.
      Specified by:
      reoptimize in interface ReoptimizableMetaheuristic<T extends Copyable<T>>
      Parameters:
      runLength - The run length for all parallel metaheuristics.
      Returns:
      The best end of run solution (and its cost) of this set of parallel runs, which may or may not be the same as the solution contained in this metaheuristic's ProgressTracker, which contains the best of all runs across all calls to optimize. Returns null if the run did not execute, such as if the ProgressTracker already contains the theoretical best solution.
      Throws:
      IllegalStateException - if the ParallelMetaheuristic.close() method was previously called.

    • split

      public ParallelReoptimizableMetaheuristic<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 ParallelMetaheuristic<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.