Examples with ExamSimpleNeighbour org.cpsolver.exam.neighbours.ExamSimpleNeighbour used on opensource projects

Example 1 with ExamSimpleNeighbour

use of org.cpsolver.exam.neighbours.ExamSimpleNeighbour in project cpsolver by UniTime.

the class ExamConstruction method selectNeighbour.

/**
     * Select a neighbour. While there are exams that are still not assigned:
     * <ul>
     * <li>The worst unassigned exam is selected (using
     * {@link Exam#compareTo(Exam)})
     * <li>The best period that does not break any hard constraint and for which
     * there is a room assignment available is selected together with the set
     * the best available rooms for the exam in the best period (computed using
     * {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)}).
     * </ul>
     * Return null when done (all variables are assigned and the problem is
     * locally optimal).
     */
@Override
public Neighbour<Exam, ExamPlacement> selectNeighbour(Solution<Exam, ExamPlacement> solution) {
    ExamModel model = (ExamModel) solution.getModel();
    Assignment<Exam, ExamPlacement> assignment = solution.getAssignment();
    Context context = getContext(assignment);
    if (!iActive) {
        iActive = true;
        // iProgress.setPhase("Construction ...", model.variables().size());
        iProgress.info("[" + Thread.currentThread().getName() + "] Construction ...");
    }
    // iProgress.setProgress(assignment.nrAssignedVariables());
    if (model.variables().size() - assignment.nrAssignedVariables() <= context.skip().size())
        return checkLocalOptimality(assignment, model);
    Exam bestExam = null;
    for (Exam exam : model.variables()) {
        if (assignment.getValue(exam) != null || context.skip().contains(exam))
            continue;
        if (bestExam == null || exam.compareTo(bestExam) < 0)
            bestExam = exam;
    }
    ExamPlacement best = null;
    for (ExamPeriodPlacement period : bestExam.getPeriodPlacements()) {
        if (bestExam.countStudentConflicts(assignment, period) > 0) {
            if (context.assignments().contains(bestExam.getId() + ":" + period.getIndex()))
                continue;
        }
        if (!bestExam.checkDistributionConstraints(assignment, period))
            continue;
        ExamPlacement placement = new ExamPlacement(bestExam, period, null);
        if (best == null || best.getTimeCost(assignment) > placement.getTimeCost(assignment)) {
            Set<ExamRoomPlacement> rooms = bestExam.findBestAvailableRooms(assignment, period);
            if (rooms != null)
                best = new ExamPlacement(bestExam, period, rooms);
        }
    }
    if (best != null) {
        context.assignments().add(bestExam.getId() + ":" + best.getPeriod().getIndex());
        return new ExamSimpleNeighbour(assignment, best);
    }
    /*
           * else { for (Enumeration
           * e=bestExam.getPeriodPlacements().elements();e.hasMoreElements();) {
           * ExamPeriodPlacement period = (ExamPeriodPlacement)e.nextElement();
           * ExamPlacement placement = new ExamPlacement(bestExam, period,
           * null); if (best==null ||
           * best.getTimeCost()>placement.getTimeCost()) { Set rooms =
           * bestExam.findBestAvailableRooms(period); if (rooms!=null) best =
           * new ExamPlacement(bestExam, period, rooms); } } if (best!=null) {
           * bestExam.allowAllStudentConflicts(best.getPeriod());
           * iAssignments.add(bestExam.getId()+":"+best.getPeriod().getIndex());
           * return new ExamSimpleNeighbour(best); } }
           */
    if (!context.skip().contains(bestExam)) {
        context.skip().add(bestExam);
        return selectNeighbour(solution);
    }
    return checkLocalOptimality(assignment, model);
}

Example 2 with ExamSimpleNeighbour

use of org.cpsolver.exam.neighbours.ExamSimpleNeighbour in project cpsolver by UniTime.

the class ExamConstruction method checkLocalOptimality.

/**
     * Find a new assignment of one of the assigned exams that improves the time
     * cost {@link ExamPlacement#getTimeCost(Assignment)} and for which there is a set of
     * available rooms {@link Exam#findBestAvailableRooms(Assignment, ExamPeriodPlacement)}.
     * Return null, if there is no such assignment (the problem is considered
     * locally optimal).
     * @param assignment current assignment
     * @param model problem model
     * @return a neighbour to assign or null if none was found
     */
public Neighbour<Exam, ExamPlacement> checkLocalOptimality(Assignment<Exam, ExamPlacement> assignment, ExamModel model) {
    if (iCheckLocalOptimality) {
        Context context = getContext(assignment);
        for (Exam exam : assignment.assignedVariables()) {
            ExamPlacement current = assignment.getValue(exam);
            if (current.getTimeCost(assignment) <= 0)
                continue;
            ExamPlacement best = null;
            for (ExamPeriodPlacement period : exam.getPeriodPlacements()) {
                if (exam.countStudentConflicts(assignment, period) > 0) {
                    if (context.assignments().contains(exam.getId() + ":" + period.getIndex()))
                        continue;
                }
                if (!exam.checkDistributionConstraints(assignment, period))
                    continue;
                ExamPlacement placement = new ExamPlacement(exam, period, null);
                if (best == null || best.getTimeCost(assignment) > placement.getTimeCost(assignment)) {
                    Set<ExamRoomPlacement> rooms = exam.findBestAvailableRooms(assignment, period);
                    if (rooms != null)
                        best = new ExamPlacement(exam, period, rooms);
                }
            }
            if (best != null && best.getTimeCost(assignment) < current.getTimeCost(assignment))
                return new ExamSimpleNeighbour(assignment, best);
        }
    }
    iActive = false;
    return null;
}