001package org.cpsolver.studentsct.heuristics.selection;
002
003import java.text.DecimalFormat;
004import java.util.ArrayList;
005import java.util.Collection;
006import java.util.Collections;
007import java.util.LinkedList;
008import java.util.List;
009import java.util.Map;
010import java.util.Queue;
011
012import org.cpsolver.ifs.assignment.Assignment;
013import org.cpsolver.ifs.heuristics.NeighbourSelection;
014import org.cpsolver.ifs.model.InfoProvider;
015import org.cpsolver.ifs.model.Neighbour;
016import org.cpsolver.ifs.solution.Solution;
017import org.cpsolver.ifs.solver.Solver;
018import org.cpsolver.ifs.util.DataProperties;
019import org.cpsolver.ifs.util.Progress;
020import org.cpsolver.studentsct.heuristics.RandomizedBacktrackNeighbourSelection;
021import org.cpsolver.studentsct.model.CourseRequest;
022import org.cpsolver.studentsct.model.Enrollment;
023import org.cpsolver.studentsct.model.FreeTimeRequest;
024import org.cpsolver.studentsct.model.Request;
025
026
027/**
028 * Use backtrack neighbour selection. For all unassigned variables (in a random
029 * order), {@link RandomizedBacktrackNeighbourSelection} is being used.
030 * 
031 * <br>
032 * <br>
033 * 
034 * @version StudentSct 1.3 (Student Sectioning)<br>
035 *          Copyright (C) 2007 - 2014 Tomas Muller<br>
036 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
037 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
038 * <br>
039 *          This library is free software; you can redistribute it and/or modify
040 *          it under the terms of the GNU Lesser General Public License as
041 *          published by the Free Software Foundation; either version 3 of the
042 *          License, or (at your option) any later version. <br>
043 * <br>
044 *          This library is distributed in the hope that it will be useful, but
045 *          WITHOUT ANY WARRANTY; without even the implied warranty of
046 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
047 *          Lesser General Public License for more details. <br>
048 * <br>
049 *          You should have received a copy of the GNU Lesser General Public
050 *          License along with this library; if not see
051 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
052 */
053
054public class BacktrackSelection implements NeighbourSelection<Request, Enrollment>, InfoProvider<Request, Enrollment> {
055    private static DecimalFormat sDF = new DecimalFormat("0.00");
056    protected RandomizedBacktrackNeighbourSelection iRBtNSel = null;
057    protected Queue<Request> iRequests = null;
058    protected boolean iIncludeAssignedRequests = false;
059    
060    protected long iNbrIterations = 0;
061    protected long iTotalTime = 0;
062    protected long iNbrTimeoutReached = 0;
063    protected long iNbrNoSolution = 0;
064
065    public BacktrackSelection(DataProperties properties) {
066        iIncludeAssignedRequests = properties.getPropertyBoolean("Neighbour.IncludeAssignedRequests", iIncludeAssignedRequests);
067    }
068
069    public void init(Solver<Request, Enrollment> solver, String name) {
070        List<Request> variables = new ArrayList<Request>(iIncludeAssignedRequests ? solver.currentSolution().getModel().variables() : solver.currentSolution().getModel().unassignedVariables(solver.currentSolution().getAssignment()));
071        Collections.shuffle(variables);
072        iRequests = new LinkedList<Request>(variables);
073        if (iRBtNSel == null) {
074            try {
075                iRBtNSel = new RandomizedBacktrackNeighbourSelection(solver.getProperties());
076                iRBtNSel.init(solver);
077            } catch (Exception e) {
078                throw new RuntimeException(e.getMessage(), e);
079            }
080        }
081        Progress.getInstance(solver.currentSolution().getModel()).setPhase(name, variables.size());
082    }
083
084    @Override
085    public void init(Solver<Request, Enrollment> solver) {
086        init(solver, "Backtracking...");
087        
088        iNbrIterations = 0;
089        iNbrTimeoutReached = 0;
090        iNbrNoSolution = 0;
091        iTotalTime = 0;
092    }
093    
094    protected synchronized Request nextRequest() {
095        return iRequests.poll();
096    }
097
098    @Override
099    public Neighbour<Request, Enrollment> selectNeighbour(Solution<Request, Enrollment> solution) {
100        Request request = null;
101        while ((request = nextRequest()) != null) {
102            Progress.getInstance(solution.getModel()).incProgress();
103            Enrollment e = request.getAssignment(solution.getAssignment());
104            if (e != null && request instanceof FreeTimeRequest) continue;
105            if (e != null && e.getPriority() == 0 && ((CourseRequest)request).getSelectedChoices().isEmpty()) continue;
106            Neighbour<Request, Enrollment> n = iRBtNSel.selectNeighbour(solution, request);
107            if (iRBtNSel.getContext() != null) {
108                iNbrIterations ++;
109                iTotalTime += iRBtNSel.getContext().getTime();
110                if (iRBtNSel.getContext().isTimeoutReached()) iNbrTimeoutReached ++;
111                if (n == null) iNbrNoSolution ++;
112            }
113            if (n != null && n.value(solution.getAssignment()) <= 0.0)
114                return n;
115        }
116        return null;
117    }
118
119    @Override
120    public void getInfo(Assignment<Request, Enrollment> assignment, Map<String, String> info) {
121        if (iNbrIterations > 0)
122            info.put("Timing of " + getClass().getSimpleName(), sDF.format(((double)iTotalTime) / iNbrIterations) + " ms/it (" +
123                    iNbrIterations + " iterations, " +
124                    (iNbrNoSolution == 0 ? "" : sDF.format(100.0 * iNbrNoSolution / iNbrIterations) + "% no solution, ") +
125                    sDF.format(100.0 * iNbrTimeoutReached / iNbrIterations) + "% time limit of " + sDF.format(iRBtNSel.getTimeout() / 1000.0) + " seconds reached)"); 
126    }
127
128    @Override
129    public void getInfo(Assignment<Request, Enrollment> assignment, Map<String, String> info, Collection<Request> variables) {
130    }
131}