source: bidspace/src/main/java/geniusweb/bidspace/pareto/ParetoLinearAdditive.java@ 30

package geniusweb.bidspace.pareto;

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

import geniusweb.issuevalue.Bid;
import geniusweb.issuevalue.Domain;
import geniusweb.profile.Profile;
import geniusweb.profile.utilityspace.LinearAdditive;

/**
 * pareto frontier implementation for {@link LinearAdditive}. This is a highly
 * optimized pareto method for {@link LinearAdditive} spaces
 */
public class ParetoLinearAdditive implements ParetoFrontier {

        private final List<LinearAdditive> utilSpaces;
        private Set<Bid> points = null;
        // all issues in a deterministic order

        /**
         * 
         * @param utilSpaces. Must contain at least two {@link LinearAdditive}s and
         *                    all must be defined on the same donain.
         */
        public ParetoLinearAdditive(List<LinearAdditive> utilSpaces) {
                if (utilSpaces == null || utilSpaces.size() < 2) {
                        throw new IllegalArgumentException(
                                        "utilSpaces must contain at least 2 spaces");
                }
                Domain domain = utilSpaces.get(0).getDomain();
                for (LinearAdditive space : utilSpaces) {
                        if (!space.getDomain().equals(domain)) {
                                throw new IllegalArgumentException(
                                                "Expected all spaces using domain " + domain.getName()
                                                                + " but found " + space.getDomain().getName());
                        }
                }
                this.utilSpaces = utilSpaces;
        }

        @Override
        public List<Profile> getProfiles() {
                return Collections.unmodifiableList(utilSpaces);
        }

        @Override
        public Set<Bid> getPoints() {
                if (points == null) {
                        points = computePareto();
                }
                return points;
        }

        @Override
        public String toString() {
                return "Pareto " + getPoints();
        }

        private Set<Bid> computePareto() {
                LinkedList<String> issues = new LinkedList<>(
                                utilSpaces.get(0).getDomain().getIssues());
                PartialPareto partial = PartialPareto.create(utilSpaces, issues);
                return partial.getPoints().stream().map(point -> point.getBid())
                                .collect(Collectors.toSet());
        }

}