/**
* Copyright (c) 1999-2014, 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:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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.
* * Neither the name of the Ecole des Mines de Nantes 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 THE REGENTS AND CONTRIBUTORS ``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 THE REGENTS AND CONTRIBUTORS 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 solver.constraints.nary.nValue.amnv.mis;
import util.objects.graphs.UndirectedGraph;
import util.objects.setDataStructures.ISet;
import java.util.Random;
/**
* Min Degree + Random k heuristic
*
* @since 01/01/2014
* @author Jean-Guillaume Fages
*/
public class MDRk extends MD{
//***********************************************************************************
// VARIABLES
//***********************************************************************************
protected int k, iter;
protected Random rd;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Creates an instance of the Min Degree + Random k heuristic to compute independent sets on graph
* @param graph
* @param k number of random iterations
*/
public MDRk(UndirectedGraph graph, int k){
super(graph);
this.k=k;
this.rd = new Random(0);
}
/**
* Creates an instance of the Min Degree + Random k heuristic to compute independent sets on graph
* @param graph
*/
public MDRk(UndirectedGraph graph){
this(graph,Rk.DEFAULT_K);
}
//***********************************************************************************
// METHODS
//***********************************************************************************
@Override
public void prepare() {
iter=0;
}
@Override
public void computeMIS() {
iter++;
if(iter==1){
super.computeMIS();
}else{
computeMISRk();
}
}
protected void computeMISRk() {
iter++;
out.clear();
inMIS.clear();
while (out.cardinality() < n) {
int nb = rd.nextInt(n - out.cardinality());
int idx = out.nextClearBit(0);
for (int i = idx; i >= 0 && i < n && nb >= 0; i = out.nextClearBit(i + 1)) {
idx = i;
nb--;
}
inMIS.set(idx);
out.set(idx);
ISet nei = graph.getNeighOf(idx);
for (int j = nei.getFirstElement(); j >= 0; j = nei.getNextElement()) {
out.set(j);
}
}
}
@Override
public boolean hasNextMIS(){
return iter<k;
}
}