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Open-source constraint solver.
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/**
 * Copyright (c) 2016, Ecole des Mines de Nantes
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the .
 * 4. Neither the name of the  nor the
 *    names of its contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY  ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL  BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.chocosolver.util.graphOperations.dominance;

import org.chocosolver.util.objects.graphs.DirectedGraph;

/**
 * Class that finds dominators of a given flow graph g(s)
 * Uses the simple LT algorithm which runs in O(m.log(n))
 * Fast in practice
 */
public class SimpleDominatorsFinder extends AbstractLengauerTarjanDominatorsFinder {

    //***********************************************************************************
    // CONSTRUCTORS
    //***********************************************************************************

    /**
     * Object that finds dominators of the given flow graph g(s)
     * It uses the simple LT algorithm which runs in O(m.log(n))
     */
    public SimpleDominatorsFinder(int s, DirectedGraph g) {
        super(s, g);
    }

    //***********************************************************************************
    // link-eval
    //***********************************************************************************

    protected void link(int v, int w) {
        ancestor[w] = v;
    }

    protected int eval(int v) {
        if (ancestor[v] == -1) {
            return v;
        } else {
            compress(v);
            return label[v];
        }

    }

    protected void compress(int v) {
        int k = v;
        list.clear();
        while (ancestor[ancestor[k]] != -1) {
            list.add(k);
            k = ancestor[k];
        }
        for (k = list.size() - 1; k >= 0; k--) {
            v = list.get(k);
            if (semi[label[ancestor[v]]] < semi[label[v]]) {
                label[v] = label[ancestor[v]];
            }
            ancestor[v] = ancestor[ancestor[v]];
        }
    }
}