net.sourceforge.cilib.util.selection.recipes.TournamentSelector Maven / Gradle / Ivy

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/**           __  __
 *    _____ _/ /_/ /_    Computational Intelligence Library (CIlib)
 *   / ___/ / / / __ \   (c) CIRG @ UP
 *  / /__/ / / / /_/ /   http://cilib.net
 *  \___/_/_/_/_.___/
 */
package net.sourceforge.cilib.util.selection.recipes;

import com.google.common.collect.Iterables;
import com.google.common.collect.Ordering;
import java.util.Comparator;
import java.util.List;
import net.sourceforge.cilib.controlparameter.ControlParameter;
import net.sourceforge.cilib.controlparameter.ProportionalControlParameter;
import net.sourceforge.cilib.util.selection.PartialSelection;
import net.sourceforge.cilib.util.selection.Samples;
import net.sourceforge.cilib.util.selection.Selection;
import net.sourceforge.cilib.util.selection.arrangement.RandomArrangement;
import net.sourceforge.cilib.util.selection.arrangement.ReverseArrangement;
import net.sourceforge.cilib.util.selection.arrangement.SortedArrangement;

/**
 * A recipe for Tournament selection.
 * 
 * Tournament selection is performed by:
 * 

 *   Randomly ordering a list of elements.
 *   Selecting a sublist of {@code tournamentSize}.
 *   Sorting the created sublist.
 *   Selecting the best performing element.
 *   Return the result.
 * 
 *
 * @param  The selection type.
 */
public class TournamentSelector implements Selector {

    private static final long serialVersionUID = -6689673224380247931L;
    private ControlParameter tournamentProportion;
    private Comparator comparator;

    /**
     * Create a new instance.
     */
    public TournamentSelector() {
        this.tournamentProportion = new ProportionalControlParameter();
        this.comparator = Ordering.natural();
    }

    /**
     * Create a copy of the provided instance.
     * @param copy The instance to copy.
     */
    public TournamentSelector(TournamentSelector copy) {
        this.tournamentProportion = copy.tournamentProportion.getClone();
        this.comparator = copy.comparator;
    }

    /**
     * Get the size of the tournament.
     * @return The size of the tournament.
     */
    public ControlParameter getTournamentSize() {
        return this.tournamentProportion;
    }

    /**
     * Set the size of the tournament.
     * @param tournamanetSize The value to set.
     */
    public void setTournamentSize(ControlParameter tournamanetSize) {
        this.tournamentProportion = tournamanetSize;
    }

    /**
     * Set the comparator for the selection.
     * @param comparator The value to set.
     */
    public void setComparator(Comparator comparator) {
        this.comparator = comparator;
    }

    /**
     * Get the comparator for the selection.
     * @return The current comparator.
     */
    public Comparator getComparator() {
        return this.comparator;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public PartialSelection on(Iterable iterable) {
        int size = Iterables.size(iterable);
        int tournamentSize = Double.valueOf(this.tournamentProportion.getParameter() * size).intValue();
        List intermediate = Selection.copyOf(iterable).orderBy(new RandomArrangement()).select(Samples.last(tournamentSize));
        return Selection.copyOf(intermediate).orderBy(new SortedArrangement()).orderBy(new ReverseArrangement());
    }
}