org.cicirello.search.representations.SingleInteger Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of chips-n-salsa Show documentation

Chips-n-Salsa is a Java library of customizable, hybridizable, iterative, parallel, stochastic, and self-adaptive local search algorithms. The library includes implementations of several stochastic local search algorithms, including simulated annealing, hill climbers, as well as constructive search algorithms such as stochastic sampling. Chips-n-Salsa now also includes genetic algorithms as well as evolutionary algorithms more generally. The library very extensively supports simulated annealing. It includes several classes for representing solutions to a variety of optimization problems. For example, the library includes a BitVector class that implements vectors of bits, as well as classes for representing solutions to problems where we are searching for an optimal vector of integers or reals. For each of the built-in representations, the library provides the most common mutation operators for generating random neighbors of candidate solutions, as well as common crossover operators for use with evolutionary algorithms. Additionally, the library provides extensive support for permutation optimization problems, including implementations of many different mutation operators for permutations, and utilizing the efficiently implemented Permutation class of the JavaPermutationTools (JPT) library. Chips-n-Salsa is customizable, making extensive use of Java's generic types, enabling using the library to optimize other types of representations beyond what is provided in the library. It is hybridizable, providing support for integrating multiple forms of local search (e.g., using a hill climber on a solution generated by simulated annealing), creating hybrid mutation operators (e.g., local search using multiple mutation operators), as well as support for running more than one type of search for the same problem concurrently using multiple threads as a form of algorithm portfolio. Chips-n-Salsa is iterative, with support for multistart metaheuristics, including implementations of several restart schedules for varying the run lengths across the restarts. It also supports parallel execution of multiple instances of the same, or different, stochastic local search algorithms for an instance of a problem to accelerate the search process. The library supports self-adaptive search in a variety of ways, such as including implementations of adaptive annealing schedules for simulated annealing, such as the Modified Lam schedule, implementations of the simpler annealing schedules but which self-tune the initial temperature and other parameters, and restart schedules that adapt to run length.

There is a newer version: 7.0.1

Show newest version

/*
 * Chips-n-Salsa: A library of parallel self-adaptive local search algorithms.
 * Copyright (C) 2002-2022 Vincent A. Cicirello
 *
 * This file is part of Chips-n-Salsa (https://chips-n-salsa.cicirello.org/).
 *
 * Chips-n-Salsa is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Chips-n-Salsa is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */

package org.cicirello.search.representations;

import org.cicirello.util.Copyable;

/**
 * A simple class for representing the input to a univariate function, such that the input is an
 * integer.
 *
 * @author Vincent A. Cicirello, https://www.cicirello.org/
 */
public class SingleInteger implements IntegerValued, Copyable {

  private int x;

  /** Initializes this function input to 0. */
  public SingleInteger() {}

  /**
   * Initializes this function input to a specified value.
   *
   * @param x The initial value for this function input.
   */
  public SingleInteger(int x) {
    this.x = x;
  }

  /**
   * Initializes this function input as a copy of another.
   *
   * @param other The other function input to copy.
   */
  public SingleInteger(SingleInteger other) {
    x = other.x;
  }

  @Override
  public final int length() {
    return 1;
  }

  /**
   * Accesses the current value of this function input.
   *
   * @return The current value of this function input.
   */
  public final int get() {
    return x;
  }

  @Override
  public final int[] toArray(int[] values) {
    if (values == null || values.length != 1) values = new int[1];
    values[0] = x;
    return values;
  }

  /**
   * Accesses the current value of this function input. This method originates with the {@link
   * IntegerValued} interface. Since this is a univariate function, there is only 1 input variable
   * by definition. Rather than throw an exception for values of i other than 0, this method ignores
   * the i parameter and is equivalent to the {@link #get()} method regardless of value passed for
   * i.
   *
   * @param i The input to get (ignored by this implementation since this is an input for a
   *     univariate function).
   * @return The current value of this function input.
   */
  @Override
  public final int get(int i) {
    return x;
  }

  /**
   * Sets this function input to a specified value.
   *
   * @param x The new value for this function input.
   */
  public void set(int x) {
    this.x = x;
  }

  /**
   * Sets this function input to a specified value. This method originates with the {@link
   * IntegerValued} interface. Since this is a univariate function, there is only 1 input variable
   * by definition. Rather than throw an exception for values of i other than 0, this method ignores
   * the i parameter and is equivalent to the {@link #set(int)} method regardless of value passed
   * for i.
   *
   * This method delegates work to the {@link #set(int)} method, so the behavior of this method
   * will be consistent with any subclasses that override {@link #set(int)}.
   *
   * @param i The input variable to set (ignored by this implementation since this is an input for a
   *     univariate function).
   * @param x The new value for this function input.
   */
  @Override
  public final void set(int i, int x) {
    set(x);
  }

  /**
   * Sets this function input to a specified value. This method originates with the {@link
   * IntegerValued} interface. Since this is a univariate function, there is only 1 input variable
   * by definition. Rather than throw an exception for values.length greater than 1, this method
   * simply uses values[0] and ignores any extra values.
   *
   * This method delegates work to the {@link #set(int)} method, so the behavior of this method
   * will be consistent with any subclasses that override {@link #set(int)}.
   *
   * @param values The values to set.
   */
  @Override
  public final void set(int[] values) {
    set(values[0]);
  }

  /**
   * Creates an identical copy of this object.
   *
   * @return an identical copy of this object
   */
  @Override
  public SingleInteger copy() {
    return new SingleInteger(this);
  }

  /**
   * Indicates whether some other object is "equal to" this one. To be equal, the other object must
   * be of the same runtime type and contain the same value of the function input.
   *
   * @param other The other object to compare.
   * @return true if other is not null, is of the same runtime type as this, and contains the same
   *     function input value.
   */
  @Override
  public boolean equals(Object other) {
    if (other == null || !(other instanceof SingleInteger)) return false;
    return x == ((SingleInteger) other).x;
  }

  /**
   * Returns a hash code value.
   *
   * @return a hash code value
   */
  @Override
  public int hashCode() {
    return x;
  }
}