net.sf.cpsolver.exam.heuristics
Class ExamConstruction

java.lang.Object
  net.sf.cpsolver.exam.heuristics.ExamConstruction

All Implemented Interfaces:

NeighbourSelection

public class ExamConstruction
extends Object
implements NeighbourSelection

Initial solution construction heuristics.

While there are exams that are still not assigned:

• The worst unassigned exam is selected (using Exam.compareTo(Object))
• 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 Exam.findBestAvailableRooms(ExamPeriodPlacement)).

If problem property ExamConstruction.CheckLocalOptimality is true, local (time) optimality is enforced at the end of this phase. During this procedure, for each exam, it tries to change the period of the exam so that the time cost is lower (see ExamPlacement.getTimeCost()), but no hard constraint is violated. The problem is considered locally optimal if there is no such move.

Version:

ExamTT 1.1 (Examination Timetabling)
Copyright (C) 2008 Tomáš Müller
muller@unitime.org
Lazenska 391, 76314 Zlin, Czech Republic

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

Constructor Summary

ExamConstruction(DataProperties properties)
Constructor

Method Summary

Neighbour	checkLocalOptimality(ExamModel model) Find a new assignment of one of the assigned exams that improves the time cost ExamPlacement.getTimeCost() and for which there is a set of available rooms Exam.findBestAvailableRooms(ExamPeriodPlacement).
void	init(Solver solver) Initialization
Neighbour	selectNeighbour(Solution solution) Select a neighbour.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExamConstruction

public ExamConstruction(DataProperties properties)

Constructor

Parameters:

properties - problem properties

Method Detail

init

public void init(Solver solver)

Initialization

Specified by:

init in interface NeighbourSelection

checkLocalOptimality

public Neighbour checkLocalOptimality(ExamModel model)

Find a new assignment of one of the assigned exams that improves the time cost ExamPlacement.getTimeCost() and for which there is a set of available rooms Exam.findBestAvailableRooms(ExamPeriodPlacement). Return null, if there is no such assignment (the problem is considered locally optimal).

selectNeighbour

public Neighbour selectNeighbour(Solution solution)

Select a neighbour. While there are exams that are still not assigned:

• The worst unassigned exam is selected (using Exam.compareTo(Object))
• 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 Exam.findBestAvailableRooms(ExamPeriodPlacement)).

Return null when done (all variables are assigned and the problem is locally optimal).

Specified by:

selectNeighbour in interface NeighbourSelection

Parameters:

solution - given solution

Returns:

a neighbour assignment