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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.

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/*
 * 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.evo;

import org.cicirello.search.ProgressTracker;
import org.cicirello.search.operators.bits.BitFlipMutation;
import org.cicirello.search.operators.bits.BitVectorInitializer;
import org.cicirello.search.problems.IntegerCostOptimizationProblem;
import org.cicirello.search.problems.OptimizationProblem;
import org.cicirello.search.representations.BitVector;

/**
 * This class implements a (1+1)-GA, a special case of a (1+1)-EA, where solutions are represented
 * with a vector of bits. In a (1+1)-EA, the evolutionary algorithm has a population size of 1, in
 * each cycle of the algorithm a single mutant is created from that single population member,
 * forming a population of size 2, and finally the EA keeps the better of the two solutions. This is
 * perhaps the simplest case of an EA. This class supports optimizing BitVector objects. Mutation is
 * the standard bit-flip mutation of a genetic algorithm, where a mutation rate M specifies the
 * probability that each bit flips (from 0 to 1 or vice versa) during a mutation.
 *
 * @author Vincent A. Cicirello, https://www.cicirello.org/
 */
public final class OnePlusOneGeneticAlgorithm extends OnePlusOneEvolutionaryAlgorithm {

  /**
   * Creates a OnePlusOneGeneticAlgorithm instance for real-valued optimization problems. A {@link
   * ProgressTracker} is created for you.
   *
   * @param problem An instance of an optimization problem to solve.
   * @param m The probability of flipping each bit during a mutation, which must be greater than 0.0
   *     and less than 1.0.
   * @param bitLength The length of BitVectors required to represent solutions to the problem.
   * @throws IllegalArgumentException if m ≤ 0 or m ≥ 1 or if bitLength is negative.
   * @throws NullPointerException if problem is null.
   */
  public OnePlusOneGeneticAlgorithm(
      OptimizationProblem problem, double m, int bitLength) {
    this(problem, m, bitLength, new ProgressTracker());
  }

  /**
   * Creates a OnePlusOneGeneticAlgorithm instance for integer-valued optimization problems. A
   * {@link ProgressTracker} is created for you.
   *
   * @param problem An instance of an optimization problem to solve.
   * @param m The probability of flipping each bit during a mutation, which must be greater than 0.0
   *     and less than 1.0.
   * @param bitLength The length of BitVectors required to represent solutions to the problem.
   * @throws IllegalArgumentException if m ≤ 0 or m ≥ 1 or if bitLength is negative.
   * @throws NullPointerException if problem is null.
   */
  public OnePlusOneGeneticAlgorithm(
      IntegerCostOptimizationProblem problem, double m, int bitLength) {
    this(problem, m, bitLength, new ProgressTracker());
  }

  /**
   * Creates a OnePlusOneGeneticAlgorithm instance for real-valued optimization problems.
   *
   * @param problem An instance of an optimization problem to solve.
   * @param m The probability of flipping each bit during a mutation, which must be greater than 0.0
   *     and less than 1.0.
   * @param bitLength The length of BitVectors required to represent solutions to the problem.
   * @param tracker A ProgressTracker object, which is used to keep track of the best solution found
   *     during the run, the time when it was found, and other related data.
   * @throws IllegalArgumentException if m ≤ 0 or m ≥ 1 or if bitLength is negative.
   * @throws NullPointerException if problem is null or if tracker is null.
   */
  public OnePlusOneGeneticAlgorithm(
      OptimizationProblem problem,
      double m,
      int bitLength,
      ProgressTracker tracker) {
    super(problem, new BitFlipMutation(m), new BitVectorInitializer(bitLength), tracker);
  }

  /**
   * Creates a OnePlusOneGeneticAlgorithm instance for integer-valued optimization problems.
   *
   * @param problem An instance of an optimization problem to solve.
   * @param m The probability of flipping each bit during a mutation, which must be greater than 0.0
   *     and less than 1.0.
   * @param bitLength The length of BitVectors required to represent solutions to the problem.
   * @param tracker A ProgressTracker object, which is used to keep track of the best solution found
   *     during the run, the time when it was found, and other related data.
   * @throws IllegalArgumentException if m ≤ 0 or m ≥ 1 or if bitLength is negative.
   * @throws NullPointerException if problem is null or if tracker is null.
   */
  public OnePlusOneGeneticAlgorithm(
      IntegerCostOptimizationProblem problem,
      double m,
      int bitLength,
      ProgressTracker tracker) {
    super(problem, new BitFlipMutation(m), new BitVectorInitializer(bitLength), tracker);
  }

  /*
   * private copy constructor in support of the split method.
   */
  private OnePlusOneGeneticAlgorithm(OnePlusOneGeneticAlgorithm other) {
    super(other);
  }

  @Override
  public OnePlusOneGeneticAlgorithm split() {
    return new OnePlusOneGeneticAlgorithm(this);
  }
}