com.salesforce.jgrapht.alg.BellmanFordPathElement Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of AptSpringProcessor Show documentation

This project contains the apt processor that implements all the checks enumerated in @Verify. It is a self contained, and shaded jar.

There is a newer version: 2.0.7

Show newest version

/*
 * (C) Copyright 2006-2017, by France Telecom and Contributors.
 *
 * JGraphT : a free Java graph-theory library
 *
 * This program and the accompanying materials are dual-licensed under
 * either
 *
 * (a) the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation, or (at your option) any
 * later version.
 *
 * or (per the licensee's choosing)
 *
 * (b) the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation.
 */
package com.salesforce.jgrapht.alg;

import com.salesforce.jgrapht.*;

/**
 * Helper class for {@link BellmanFordShortestPath}; not intended for general use.
 * 
 * @deprecated moved into shortest path package
 */
@Deprecated
final class BellmanFordPathElement
    extends AbstractPathElement
{
    private double cost = 0;
    private double epsilon;

    /**
     * Creates a path element by concatenation of an edge to a path element.
     *
     * @param pathElement
     * @param edge edge reaching the end vertex of the path element created.
     * @param cost total cost of the created path element.
     * @param epsilon tolerance factor.
     */
    protected BellmanFordPathElement(
        Graph graph, BellmanFordPathElement pathElement, E edge, double cost,
        double epsilon)
    {
        super(graph, pathElement, edge);

        this.cost = cost;
        this.epsilon = epsilon;
    }

    /**
     * Copy constructor.
     *
     * @param original source to copy from
     */
    BellmanFordPathElement(BellmanFordPathElement original)
    {
        super(original);
        this.cost = original.cost;
        this.epsilon = original.epsilon;
    }

    /**
     * Creates an empty path element.
     *
     * @param vertex end vertex of the path element.
     * @param epsilon tolerance factor.
     */
    protected BellmanFordPathElement(V vertex, double epsilon)
    {
        super(vertex);

        this.cost = 0;
        this.epsilon = epsilon;
    }

    /**
     * Returns the total cost of the path element.
     *
     * @return .
     */
    public double getCost()
    {
        return this.cost;
    }

    /**
     * Returns true if the path has been improved, 
     * false otherwise. We use an "epsilon" precision to check whether the cost has been
     * improved (because of many roundings, a formula equal to 0 could unfortunately be evaluated to
     * 10^-14).
     *
     * @param candidatePrevPathElement
     * @param candidateEdge
     * @param candidateCost
     *
     * @return .
     */
    protected boolean improve(
        BellmanFordPathElement candidatePrevPathElement, E candidateEdge,
        double candidateCost)
    {
        // to avoid improvement only due to rounding errors.
        if (candidateCost < (getCost() - epsilon)) {
            this.prevPathElement = candidatePrevPathElement;
            this.prevEdge = candidateEdge;
            this.cost = candidateCost;
            this.nHops = candidatePrevPathElement.getHopCount() + 1;

            return true;
        } else {
            return false;
        }
    }
}

// End BellmanFordPathElement.java