io.github.ericmedvet.jgea.problem.mapper.FitnessFunction Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of jgea.problem Show documentation
Problem (benchmarks and templates) for jgea.
The newest version!
/*-
 * ========================LICENSE_START=================================
 * jgea-problem
 * %%
 * Copyright (C) 2018 - 2024 Eric Medvet
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * =========================LICENSE_END==================================
 */

package io.github.ericmedvet.jgea.problem.mapper;

import io.github.ericmedvet.jgea.core.distance.BitStringHamming;
import io.github.ericmedvet.jgea.core.distance.Distance;
import io.github.ericmedvet.jgea.core.operator.GeneticOperator;
import io.github.ericmedvet.jgea.core.representation.sequence.bit.BitString;
import io.github.ericmedvet.jgea.core.representation.sequence.bit.BitStringFactory;
import io.github.ericmedvet.jgea.core.representation.sequence.bit.BitStringFlipMutation;
import io.github.ericmedvet.jgea.core.representation.tree.Tree;
import io.github.ericmedvet.jgea.core.util.LinkedHashMultiset;
import io.github.ericmedvet.jgea.core.util.Multiset;
import io.github.ericmedvet.jnb.datastructure.Pair;
import java.util.*;
import java.util.function.Function;
import org.apache.commons.math3.stat.StatUtils;
import org.apache.commons.math3.stat.correlation.PearsonsCorrelation;

public class FitnessFunction implements Function, Tree>, List> {

  private static final int EXPRESSIVENESS_DEPTH = 2;
  private final List problems;
  private final int maxMappingDepth;
  private final List properties;
  private final List genotypes;
  private final double[] genotypeDistances;

  public FitnessFunction(
      List problems,
      int genotypeSize,
      int n,
      int maxMappingDepth,
      List properties,
      long seed) {
    this.problems = problems;
    this.maxMappingDepth = maxMappingDepth;
    this.properties = properties;
    Random random = new Random(seed);
    // build genotypes
    GeneticOperator mutation = new BitStringFlipMutation(0.01d);
    BitStringFactory factory = new BitStringFactory(genotypeSize);
    Set set = new LinkedHashSet<>();
    for (int i = 0; i < Math.floor(Math.sqrt(n)); i++) {
      set.addAll(consecutiveMutations(factory.build(random), (int) Math.floor(Math.sqrt(n)), mutation, random));
    }
    while (set.size() < n) {
      set.add(factory.build(random));
    }
    genotypes = new ArrayList<>(set);
    // compute distances
    genotypeDistances = computeDistances(genotypes, new BitStringHamming());
  }

  public enum Property {
    DEGENERACY,
    NON_UNIFORMITY,
    NON_LOCALITY
  }

  @SuppressWarnings({"rawtypes", "unchecked"})
  @Override
  public List apply(Pair, Tree> pair) {
    List> valuesLists = new ArrayList<>();
    for (EnhancedProblem problem : problems) {
      List localValues = apply(pair, problem);
      if (valuesLists.isEmpty()) {
        localValues.forEach(v -> {
          List valuesList = new ArrayList<>(problems.size());
          valuesLists.add(valuesList);
        });
      }
      for (int i = 0; i < localValues.size(); i++) {
        valuesLists.get(i).add(localValues.get(i));
      }
    }
    return valuesLists.stream()
        .map(valuesList -> valuesList.stream()
            .mapToDouble(Double::doubleValue)
            .average()
            .orElse(Double.NaN))
        .toList();
  }

  protected  List apply(Pair, Tree> pair, EnhancedProblem problem) {
    // build mapper
    RecursiveMapper recursiveMapper = new RecursiveMapper<>(
        pair.first(),
        pair.second(),
        maxMappingDepth,
        EXPRESSIVENESS_DEPTH,
        problem.problem().getGrammar());
    // map
    List solutions = genotypes.stream()
        .map(recursiveMapper)
        .map(t -> problem.problem().getSolutionMapper().apply(t))
        .toList();
    Multiset multiset = new LinkedHashMultiset<>(solutions);
    multiset.addAll(solutions);
    // compute properties
    List values = new ArrayList<>();
    for (Property property : properties) {
      if (property.equals(Property.DEGENERACY)) {
        values.add(1d - (double) multiset.elementSet().size() / (double) genotypes.size());
      } else if (property.equals(Property.NON_UNIFORMITY)) {
        double[] sizes = multiset.elementSet().stream()
            .mapToDouble(multiset::count)
            .toArray();
        values.add(Math.sqrt(StatUtils.variance(sizes)) / StatUtils.mean(sizes));
      } else if (property.equals(Property.NON_LOCALITY)) {
        double[] solutionDistances = computeDistances(solutions, problem.distance());
        double locality =
            1d - (1d + (new PearsonsCorrelation().correlation(genotypeDistances, solutionDistances))) / 2d;
        values.add(Double.isNaN(locality) ? 1d : locality);
      } else {
        values.add(0d);
      }
    }
    return values;
  }

  private  double[] computeDistances(List elements, Distance distance) {
    double[] dists = new double[elements.size() * (elements.size() - 1) / 2];
    int c = 0;
    for (int i = 0; i < elements.size() - 1; i++) {
      for (int j = i + 1; j < elements.size(); j++) {
        dists[c] = distance.apply(elements.get(i), elements.get(j));
        c = c + 1;
      }
    }
    return dists;
  }

  private List consecutiveMutations(
      BitString g, int n, GeneticOperator mutation, Random random) {
    Set set = new LinkedHashSet<>();
    while (set.size() < n) {
      set.add(g);
      g = mutation.apply(Collections.singletonList(g), random).getFirst();
    }
    return new ArrayList<>(set);
  }
}