@syntest/search/dist/lib/algorithms/evolutionary/NSGAII.js

The common core of the SynTest Framework

"use strict";
/*
 * Copyright 2020-2021 Delft University of Technology and SynTest contributors
 *
 * This file is part of SynTest Framework - SynTest Core.
 *
 * 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.
 */
Object.defineProperty(exports, "__esModule", { value: true });
exports.NSGAII = void 0;
const CrowdingDistance_1 = require("../../operators/ranking/CrowdingDistance");
const FastNonDomSorting_1 = require("../../operators/ranking/FastNonDomSorting");
const EvolutionaryAlgorithm_1 = require("./EvolutionaryAlgorithm");
/**
 * Non-dominated Sorting Genetic Algorithm (NSGA-II).
 *
 * Based on:
 * A fast and elitist multiobjective genetic algorithm: NSGA-II
 * K. Deb; A. Pratap; S. Agarwal; T. Meyarivan
 *
 * @author Mitchell Olsthoorn
 * @author Annibale Panichella
 * @author Dimitri Stallenberg
 */
class NSGAII extends EvolutionaryAlgorithm_1.EvolutionaryAlgorithm {
    /**
     * @inheritDoc
     * @protected
     */
    _environmentalSelection(size) {
        const F = (0, FastNonDomSorting_1.fastNonDomSorting)(this._population, this._objectiveManager.getCurrentObjectives());
        // select new population
        const nextPopulation = [];
        let remain = size;
        let index = 0;
        // Obtain the next front
        let currentFront = F[index];
        while (remain > 0 && remain >= currentFront.length) {
            // Assign crowding distance to individuals
            (0, CrowdingDistance_1.crowdingDistance)(currentFront, this._objectiveManager.getCurrentObjectives());
            // Add the individuals of this front
            nextPopulation.push(...currentFront);
            // Decrement remain
            remain = remain - currentFront.length;
            // Obtain the next front
            index++;
            currentFront = F[index];
        }
        // Remain is less than front(index).size, insert only the best one
        if (remain > 0 && currentFront.length > 0) {
            // front contains individuals to insert
            (0, CrowdingDistance_1.crowdingDistance)(currentFront, this._objectiveManager.getCurrentObjectives());
            // sort in descending order of crowding distance
            currentFront.sort((a, b) => b.getCrowdingDistance() - a.getCrowdingDistance());
            for (const individual of currentFront) {
                if (remain === 0)
                    break;
                nextPopulation.push(individual);
                remain--;
            }
        }
        this._population = nextPopulation;
    }
}
exports.NSGAII = NSGAII;
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