Module org.cicirello.chips_n_salsa
Package org.cicirello.search.sa

Class ModifiedLamOriginal

java.lang.Object
org.cicirello.search.sa.ModifiedLamOriginal
All Implemented Interfaces:
Splittable<AnnealingSchedule>, AnnealingSchedule
public final class ModifiedLamOriginal extends Object implements AnnealingSchedule
This class implements the Modified Lam annealing schedule, which dynamically adjusts simulated annealing's temperature parameter up and down to either decrease or increase the neighbor acceptance rate as necessary to attempt to match a theoretically determined ideal. The Modified Lam annealing schedule is a practical realization of Lam and Delosme's (1988) schedule, refined first by Swartz (1993) and then further by Boyan (1998). For complete details of the Modified Lam schedule, along with its origins and rationale, see the following references:
  • Lam, J., and Delosme, J. 1988. Performance of a new annealing schedule. In Proc. 25th ACM/IEEE DAC, 306–311.
  • Swartz, W. P. 1993. Automatic Layout of Analog and Digital Mixed Macro/Standard Cell Integrated Circuits. Ph.D. Dissertation, Yale University.
  • Boyan, J. A. 1998. Learning Evaluation Functions for Global Optimization. Ph.D. Dissertation, Carnegie Mellon University, Pittsburgh, PA.

This class, ModifiedLamOriginal, is a direct implementation of the Modified Lam schedule as described in the reference to Boyan above. In most cases, if you want to use the Modified Lam schedule, you should prefer the ModifiedLam class, which includes a variety of optimizations to speed up the updating of schedule parameters. This ModifiedLamOriginal class is included in the library for investigating the benefit of the optimizations incorporated into the ModifiedLam class (see that class's documentation for a description of the specific optimizations made).

The accept(double, double) methods of this class use the classic, and most common, Boltzmann distribution for determining whether to accept a neighbor.

  • Constructor Summary

    Constructors
    Constructor
    Description
    ModifiedLamOriginal()
    Default constructor.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    accept(double neighborCost, double currentCost)
    Determine whether or not to accept a neighboring solution based on its cost and the current cost, both passed as parameters.
    void
    init(int maxEvals)
    Perform any initialization necessary for the annealing schedule at to the start of a run of simulated annealing.
    ModifiedLamOriginal
    split()
    Generates a functionally identical copy of this object, for use in multithreaded implementations of search algorithms.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • ModifiedLamOriginal

      public ModifiedLamOriginal()
      Default constructor. The Modified Lam annealing schedule, unlike other annealing schedules, has no control parameters other than the run length (the maxEvals parameter of the init(int) method), so no parameters need be passed to the constructor.

  • Method Details

    • init

      public void init(int maxEvals)
      Description copied from interface: AnnealingSchedule
      Perform any initialization necessary for the annealing schedule at to the start of a run of simulated annealing. This includes initializing the temperature parameter. This method is called once by implementations of simulated annealing at the start of the run. Implementations of simulated annealing that perform reannealing will also call this once at the start of each reanneal.
      Specified by:
      init in interface AnnealingSchedule
      Parameters:
      maxEvals - The maximum length of the run of simulated annealing about to start. Some annealing schedules depend upon prior knowledge of run length. For those annealing schedules that don't depend upon run length, this parameter is ignored.

    • accept

      public boolean accept(double neighborCost, double currentCost)
      Description copied from interface: AnnealingSchedule
      Determine whether or not to accept a neighboring solution based on its cost and the current cost, both passed as parameters. Lower cost indicates better solution. This method must also update the temperature and any other state data related to the annealing schedule.
      Specified by:
      accept in interface AnnealingSchedule
      Parameters:
      neighborCost - The cost of the neighboring solution under consideration.
      currentCost - The cost of the current solution.
      Returns:
      true if simulated annealing should accept the neighbor, and false otherwise.

    • split

      public ModifiedLamOriginal 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<AnnealingSchedule>
      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.